Author: "Polyakov, V A." / Publication Type: Reports - Searchworks@Jio Institute Digital Library Search Results

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115 results on '"Polyakov, V A."'

1. Proof of principle for a light dark matter search with low-energy positron beams at NA64

Author: Andreev, Yu. M., Antonov, A., Torres, M. A. Ayala, Banerjee, D., Oberhauser, B. Banto, Bautin, V., Bernhard, J., Bisio, P., Bondì, M., Celentano, A., Charitonidis, N., Crivelli, P., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gertsenberger, S. V., Girod, S., Gninenko, S. N., Hösgen, M., Kambar, Y., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marini, A., Marsicano, L., Matveev, V. A., Fredes, R. Mena, Yanssen, R. Mena, Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Salamatin, K., Samoylenko, V. D., Sieber, H., Shchukin, D., Soto, O., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Tuzi, M., Ulloa, P., Volkov, P. V., Voronchikhin, I. V., Zamora-Saá, J., and Zhevlakov, A. S.
Subjects: High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract: Thermal light dark matter (LDM) with particle masses in the 1 MeV - 1 GeV range could successfully explain the observed dark matter abundance as a relic from the primordial Universe. In this picture, a new feeble interaction acts as a "portal" between the Standard Model and LDM particles, allowing for the exploration of this paradigm at accelerator experiments. In the last years, the "missing energy" experiment NA64e at CERN SPS (Super Proton Synchrotron) has set world-leading constraints in the vector-mediated LDM parameter space, by exploiting a 100 GeV electron beam impinging on an electromagnetic calorimeter, acting as an active target. In this paper, we report a detailed description of the analysis of a preliminary measurement with a 70 GeV positron beam at NA64e, performed during summer 2023 with an accumulated statistic of 1.6 x 10^10 positrons on target. This data set was analyzed with the primary aim of evaluating the performance of the NA64e detector with a lower energy positron beam, towards the realization of the post-LS3 program. The analysis results, other than additionally probing unexplored regions in the LDM parameter space, provide valuable information towards the future NA64e positron campaign.
Published: 2025

2. Measurement of the hard exclusive $\pi^{0}$ muoproduction cross section at COMPASS

Author: Alexeev, G. D., Alexeev, M. G., Alice, C., Amoroso, A., Andrieux, V., Anosov, V., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Barth, J., Beck, R., Beckers, J., Bedfer, Y., Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Chang, W. -C., Chatterjee, C., Chiosso, M., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Delcarro, F., Denisenko, I., Denisov, O. Yu., Dehpour, M., Donskov, S. V., Doshita, N., Dreisbach, Ch., Dünnweber, W., Dusaev, R. R., Ecker, D., Eremeev, D., Faccioli, P., Faessler, M., Finger, M., Finger Jr., M., Fischer, H., Flöthner, K. J., Florian, W., Friedrich, J. M., Frolov, V., Ordòñez, L. G. Garcia, Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, D., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Grüner, M., Guskov, A., Haas, P., von Harrach, D., Hoffmann, M., d'Hose, N., Hsieh, C. -Y., Ishimoto, S., Ivanov, A., Iwata, T., Jary, V., Joosten, R., Jörg, P., Kabuß, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Horikawa, K. Kondo, Konorov, I., Korzenev, A. Yu., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Kunne, F., Kurek, K., Kurjata, R. P., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Makke, N., Mallot, G. K., Maltsev, A., Martin, A., Marzec, J., Matoušek, J., Matsuda, T., Pires, C. Menezes, Metzger, F., Meyer, W., Mikhasenko, M., Mitrofanov, E., Miura, D., Miyachi, Y., Molina, R., Moretti, A., Nagaytsev, A., Neyret, D., Niemiec, M., Nový, J., Nowak, W. -D., Nukazuka, G., Olshevsky, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pešek, M., Peshekhonov, D. V., Pešková, M., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Quintans, C., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rychter, A., Rymbekova, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sinha, L., Spülbeck, D., Srnka, A., Stolarski, M., Sulc, M., Suzuki, H., Tessaro, S., Tessarotto, F., Thiel, A., Tosello, F., Townsend, A., Triloki, T., Tskhay, V., Valinoti, B., Veit, B. M., Veloso, J. F. C. A., Ventura, B., Vidon, A., Vijayakumar, A., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: A new and detailed measurement of the cross section for hard exclusive neutral-pion muoproduction on the proton was performed in a wide kinematic region, with the photon virtuality $Q^2$ ranging from 1 to 8 (GeV/$c$)$^{\rm\, 2}$ and the Bjorken variable $x_{\rm Bj}$ ranging from 0.02 to 0.45. The data were collected at COMPASS at CERN using 160 GeV/$c$ longitudinally polarised $\mu^+$ and $\mu^-$ beams scattering off a 2.5 m long liquid hydrogen target. From the average of the measured $\mu^+$ and $\mu^-$ cross sections, the virtual-photon--proton cross section is determined as a function of the squared four-momentum transfer between the initial and final state proton in the range 0.08 (GeV/$c$)$^{\rm\, 2}$ $< |t| <$ 0.64 (GeV/$c$)$^{\rm\, 2}$. From its angular distribution, the combined contribution of transversely and longitudinally polarised photons are determined, as well as transverse--transverse and longitudinal--transverse interference contributions. They are studied as functions of four-momentum transfer $|t|$, photon virtuality $Q^2$ and virtual-photon energy $\nu$. The longitudinal--transverse interference contribution is found to be compatible with zero. The significant transverse--transverse interference contribution reveals the existence of a dominant contribution by transversely polarized photons. This provides clear experimental evidence for the chiral-odd GPD $\overline{E}_T$. In addition, the existence of a non-negligible contribution of longitudinally polarized photons is suggested by the $|t|$-dependence of the cross section at $x_{\rm Bj} < $ 0.1 . Altogether, these results provide valuable input for future modelling of GPDs and thus of cross sections for exclusive pseudo-scalar meson production. Furthermore, they can be expected to facilitate the study of next-to-leading order corrections and higher-twist contributions.
Published: 2024

3. Multiplicities of positive and negative pions, kaons and unidentified hadrons from deep-inelastic scattering of muons off a liquid hydrogen target

Author: Alexeev, G. D., Alexeev, M. G., Alice, C., Amoroso, A., Andrieux, V., Anosov, V., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Barth, J., Beck, R., Beckers, J., Bedfer, Y., Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Chang, W. -C., Chatterjee, C., Chiosso, M., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Delcarro, F., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Dünnweber, W., Dusaev, R. R., Ecker, D., Eremeev, D., Faccioli, P., Faessler, M., Finger, M., Finger jr., M., Fischer, H., Flöthner, K. J., Florian, W., Friedrich, J. M., Frolov, V., Ordòñez, L. G. Garcia, Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, D., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Grüner, M., Guskov, A., Haas, P., von Harrach, D., Hoffmann, M., d'Hose, N., Hsieh, C. -Y., Ishimoto, S., Ivanov, A., Iwata, T., Jary, V., Joosten, R., Kabuß, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khatun, A., Khaustov, G. V., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Horikawa, K. Kondo, Konorov, I., Korzenev, A. Yu., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Kunne, F., Kurek, K., Kurjata, R. P., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Makke, N., Mallot, G. K., Maltsev, A., Martin, A., Marzec, J., Matoušek, J., Matsuda, T., Pires, C. Menezes, Metzger, F., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Miura, D., Miyachi, Y., Molina, R., Moretti, A., Nagaytsev, A., Neyret, D., Niemiec, M., Nový, J., Nowak, W. -D., Nukazuka, G., Olshevsky, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pešek, M., Peshekhonov, D. V., Pešková, M., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Quintans, C., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rychter, A., Rymbekova, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sinha, L., Spülbeck, D., Srnka, A., Stolarski, M., Sulc, M., Suzuki, H., Tessaro, S., Tessarotto, F., Thiel, A., Tosello, F., Townsend, A., Triloki, T., Tskhay, V., Valinoti, B., Veit, B. M., Veloso, J. F. C. A., Vijayakumar, A., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: The multiplicities of positive and negative pions, kaons and unidentified hadrons produced in deep-inelastic scattering are measured in bins of the Bjorken scaling variable $x$, the relative virtual-photon energy $y$ and the fraction of the virtual-photon energy transferred to the final-state hadron $z$. Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam of both electric charges and a liquid hydrogen target. These measurements cover the kinematic domain with photon virtuality $Q^2 > 1$ (GeV/$c)^2$, $0.004 < x < 0.4$, $0.1 < y < 0.7$ and $0.2 < z < 0.85$, in accordance with the kinematic domain used in earlier published COMPASS multiplicity measurements with an isoscalar target. The calculation of radiative corrections was improved by using the Monte Carlo generator DJANGOH, which results in up to 12\% larger corrections in the low-$x$ region., Comment: 19 pages, 29 figures
Published: 2024

4. Shedding light on Dark Sectors with high-energy muons at the NA64 experiment at the CERN SPS

Author: Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Charitonidis, N., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gertsenberger, S. V., Girod, S., Gninenko, S. N., Hösgen, M., Joosten, R., Kachanov, V. A., Kambar, Y., Karneyeu, A. E., Kasianova, E. A., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Fredes, R. Mena, Yanssen, R. G. Mena, Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Salamatin, K. M., Samoylenko, V. D., Shchukin, D. A., Soto, O., Sieber, H., Tikhomirov, V. O., Tlisova, I. V., Toropin, A. N., Tuzi, M., Veit, B. M., Volkov, P. V., Volkov, V. Yu., Voronchikhin, I. V., Zamora-Saá, J., and Zhevlakov, A. S.
Subjects: High Energy Physics - Experiment
Abstract: A search for Dark Sectors is performed using the unique M2 beam line at the CERN Super Proton Synchrotron. New particles ($X$) could be produced in the bremsstrahlung-like reaction of high energy 160 GeV muons impinging on an active target, $\mu N\rightarrow\mu NX$, followed by their decays, $X\rightarrow\text{invisible}$. The experimental signature would be a scattered single muon from the target, with about less than half of its initial energy and no activity in the sub-detectors located downstream the interaction point. The full sample of the 2022 run is analyzed through the missing energy/momentum channel, with a total statistics of $(1.98\pm0.02)\times10^{10}$ muons on target. We demonstrate that various muon-philic scenarios involving different types of mediators, such as scalar or vector particles, can be probed simultaneously with such a technique. For the vector-case, besides a $L_\mu-L_\tau$ $Z'$ vector boson, we also consider an invisibly decaying dark photon ($A'\rightarrow\text{invisible}$). This search is complementary to NA64 running with electrons and positrons, thus, opening the possibility to expand the exploration of the thermal light dark matter parameter space by combining the results obtained with the three beams., Comment: 24 pages, 22 figures
Published: 2024

5. The upper limit on the $K^+ \to \pi^0\pi^0\pi^0e^+\nu$ decay

Author: Kulik, A. V., Filippov, S. N., Gushchin, E. N., Khudyakov, A. A., Kravtsov, V. I., Kudenko, Yu. G., Polyarush, A. Yu., Artamonov, A. V., Donskov, S. V., Filin, A. P., Gorin, A. M., Inyakin, A. V., Khaustov, G. V., Kholodenko, S. A., Kolosov, V. N., Konoplyannikov, A. K., Kurshetsov, V. F., Lishin, V. A., Medynsky, M. V., Obraztsov, V. F., Okhotnikov, A. V., Polyakov, V. A., Romanovsky, V. I., Rykalin, V. I., Sadovsky, A. S., Samoylenko, V. D., Tiurin, I. S., Uvarov, V. A., and Yushchenko, O. P.
Subjects: High Energy Physics - Experiment
Abstract: A search for the $K^{+} \to \pi^{0}\pi^{0}\pi^{0}e^+\nu$ decay is performed by the OKA collaboration. The search is based on $3.65 \times 10^9 ~ K^+$ decays. No signal is observed. The upper limit set is $BR(K^{+} \to \pi^{0}\pi^{0}\pi^{0}e^+\nu) < 5.4\times 10^{-8} ~ 90\%$ CL, 65 times lower than the one currently listed by PDG.
Published: 2024

6. 50 GeV $\pi^-$ in, nothing out: a sensitive probe of invisible $\eta$ and $\eta'$ decays with NA64h

Author: Andreev, Yu. M., Antonov, A., Torres, M. A. Ayala, Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Celentano, A., Charitonidis, N., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gertsenberger, S. V., Girod, S., Gninenko, S. N., Hosgen, M., Kachanov, V. A., Kambar, Y., Karneyeu, A. E., Kekelidze, G. D., Ketzer, B., Kirpichnikov, D. V., Kolosov, V. N., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Marini, A., Marsicano, L., Matveev, V. A., Fredes, R. Mena, Yanssen, R. G. Mena, Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Salamatin, K. M., Samoylenko, V. D., Sieber, H., Shchukin, D. A., Soto, O., Tikhomirov, V. O., Tlisova, I. V., Toropin, A. N., Tuzi, M., Volkov, P. V., Volkov, V. Yu., Voronchikhin, I. V., Zamora-Saa, J., and Zhevlakov, A. S.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We present the first results from a proof-of-concept search for dark sectors via invisible decays of pseudoscalar $\eta$ and $\eta'$ mesons in the NA64h experiment at the CERN SPS. Our novel technique uses the charge-exchange reaction of 50 GeV $\pi^-$ on nuclei of an active target as the source of neutral mesons. The $\eta, \eta' \to invisible$ events would exhibit themselves via a striking signature - the complete disappearance of the incoming beam energy in the detector. No evidence for such events has been found with $2.9\times10^{9}$ pions on target accumulated during one day of data taking. This allows us to set a stringent limit on the branching ratio ${\rm Br}(\eta' \to invisible) < 2.1 \times 10^{-4}$ improving the current bound by a factor of $\simeq3$. We also set a limit on ${\rm Br}(\eta \to invisible) < 1.1 \times 10^{-4}$ comparable with the existing one. These results demonstrate the great potential of our approach and provide clear guidance on how to enhance and extend the sensitivity for dark sector physics from future searches for invisible neutral meson decays., Comment: 5 pages, 3 figures
Published: 2024

7. First constraints on the $L_\mu-L_\tau$ explanation of the muon $g-2$ anomaly from NA64-$e$ at CERN

Author: Andreev, Yu. M., Antonov, A., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Celentano, A., Charitonidis, N., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hösgen, M., Kachanov, V. A., Kambar, Y., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Gertsenberger, S. V., Girod, S., Kasianova, E. A., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marini, A., Marsicano, L., Matveev, V. A., Fredes, R. Mena, Yanssen, R. Mena, Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Salamatin, K., Samoylenko, V. D., Sieber, H., Shchukin, D., Soto, O., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Tuzi, M., Ulloa, P., Volkov, P. V., Volkov, V. Yu., Voronchikhin, I. V., Zamora-Saá, J., and Zhevlako, A. S.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: The inclusion of an additional $U(1)$ gauge $L_\mu-L_\tau$ symmetry would release the tension between the measured and the predicted value of the anomalous muon magnetic moment: this paradigm assumes the existence of a new, light $Z^\prime$ vector boson, with dominant coupling to $\mu$ and $\tau$ leptons and interacting with electrons via a loop mechanism. The $L_\mu-L_\tau$ model can also explain the Dark Matter relic abundance, by assuming that the $Z'$ boson acts as a "portal" to a new Dark Sector of particles in Nature, not charged under known interactions. In this work we present the results of the $Z'$ search performed by the NA64-$e$ experiment at CERN SPS, that collected $\sim 9\times10^{11}$ 100 GeV electrons impinging on an active thick target. Despite the suppressed $Z'$ production yield with an electron beam, NA64-$e$ provides the first accelerator-based results excluding the $g-2$ preferred band of the $Z'$ parameter space in the 1 keV $ < m_{Z'} \lesssim 2$ MeV range, in complementarity with the limits recently obtained by the NA64-$\mu$ experiment with a muon beam., Comment: 15 pages, 5 figures. New version with extended exclusion limits down to 1 keV in Z' mass
Published: 2024

8. Exploration of the Muon $g-2$ and Light Dark Matter explanations in NA64 with the CERN SPS high energy muon beam

Author: Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Charitonidis, N., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Silva, R. B. Galleguillos, Gardikiotis, A., Gertsenberger, S. V., Girod, S., Gninenko, S. N., Hoesgen, M., Kachanov, V. A., Kambar, Y., Karneyeu, A. E., Kasianova, E. A., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Fredes, R. Mena, Yanssen, R. G. Mena, Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Salamatin, K. M., Samoylenko, V. D., Shchukin, D. A., Soto, O., Sieber, H., Tikhomirov, V. O., Tlisova, I. V., Toropin, A. N., Tuzi, M., Veit, M. B., Volkov, P. V., Volkov, V. Yu., Voronchikhin, I. V., Zamora-Saa, J., and Zhevlakov, A. S.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We report on a search for a new $Z'$ ($L_\mu-L_\tau$) vector boson performed at the NA64 experiment employing a high energy muon beam and a missing energy-momentum technique. Muons from the M2 beamline at the CERN Super Proton Synchrotron with a momentum of 160 GeV/c are directed to an active target. A signal event is a single scattered muon with momentum $<$ 80 GeV/c in the final state, accompanied by missing energy, i.e. no detectable activity in the downstream calorimeters. For a total statistic of $(1.98\pm0.02)\times10^{10}$ muons on target, no event is observed in the expected signal region. This allows us to set new limits on part of the remaining $(m_{Z'},\ g_{Z'})$ parameter space which could provide an explanation for the muon $(g-2)_\mu$ anomaly. Additionally, our study excludes part of the parameter space suggested by the thermal Dark Matter relic abundance. Our results pave the way to explore Dark Sectors and light Dark Matter with muon beams in a unique and complementary way to other experiments., Comment: 5 pages, 4 figures
Published: 2024

9. High-statistics measurement of Collins and Sivers asymmetries for transversely polarised deuterons

Author: Alexeev, G. D., Alexeev, M. G., Alice, C., Amoroso, A., Andrieux, V., Anosov, V., Asatryan, S., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Barth, J., Beck, R., Beckers, J., Bedfer, Y., Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Delcarro, F., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Dunnweber, W., Dusaev, R. R., Ecker, D., Eremeev, D., Faccioli, P., Faessler, M., Finger, M., Finger jr., M., Fischer, H., Flothner, K. J., Florian, W., Friedrich, J. M., Frolov, V., Ordonez, L. G. Garcia, Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, D., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Gruner, M., Guskov, A., Haas, P., von Harrach, D., Hoffmann, M., Hoghmrtsyan, A., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jary, V., Joosten, R., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khatun, A., Khaustov, G. V., Klasek, T., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Horikawa, K. Kondo, Konorov, I., Konstantinov, V. F., Korzenev, A. Yu., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makke, N., Mallot, G. K., Maltsev, A., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Mattson, G., Pires, C. Menezes, Metzger, F., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Miura, D., Miyachi, Y., Molina, R., Moretti, A., Movsisyan, A., Nagaytsev, A., Neyret, D., Niemiec, M., Novy, J., Nowak, W. -D., Nukazuka, G., Olshevsky, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pesek, M., Peshekhonov, D. V., Peskova, M., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Quaresma, M., Quintans, C., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rychter, A., Rymbekova, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sharko, K., Sinha, L., Spulbeck, D., Srnka, A., Stolarski, M., Sulc, M., Suzuki, H., Takanashi, Y., Tessaro, S., Tessarotto, F., Thiel, A., Tosello, F., Townsend, A., Triloki, T., Tskhay, V., Valinoti, B., Veit, B. M., Veloso, J. F. C. A., Ventura, B., Vijayakumar, A., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: New results are presented on a high-statistics measurement of Collins and Sivers asymmetries of charged hadrons produced in deep inelastic scattering of muons on a transversely polarised $^6$LiD target. The data were taken in 2022 with the COMPASS spectrometer using the 160 \gevv\ muon beam at CERN, balancing the existing data on transversely polarised proton targets. The first results from about two-thirds of the new data have total uncertainties smaller by up to a factor of three compared to the previous deuteron measurements. Using all the COMPASS proton and deuteron results, both the transversity and the Sivers distribution functions of the $u$ and $d$ quark, as well as the tensor charge in the measured $x$-range are extracted. In particular, the accuracy of the $d$ quark results is significantly improved.
Published: 2023

10. Final COMPASS results on the transverse-spin-dependent azimuthal asymmetries in the pion-induced Drell-Yan process

Author: Alexeev, G. D., Alexeev, M. G., Alice, C., Amoroso, A., Andrieux, V., Anosov, V., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Barth, J., Beck, R., Beckers, J., Bedfer, Y., Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Delcarro, F., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Dunnweber, W., Dusaev, R. R., Ecker, D., Eremeev, D., Faccioli, P., Faessler, M., Finger, M., Finger jr., M., Fischer, H., Flothner, K. J., Florian, W., Friedrich, J. M., Frolov, V., Ordonez, L. G. Garcia, Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, D., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Gruner, M., Guskov, A., Haas, P., von Harrach, D., Heitz, R., Hoffmann, M., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jary, V., Joosten, R., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khatun, A., Khaustov, G. V., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Horikawa, K. Kondo, Konorov, I., Konstantinov, V. F., Korzenev, A. Yu., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makke, N., Mallot, G. K., Maltsev, A., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Mattson, G., Pires, C. Menezes, Metzger, F., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Miura, D., Miyachi, Y., Molina, R., Moretti, A., Nagaytsev, A., Neyret, D., Niemiec, M., Novy, J., Nowak, W. -D., Nukazuka, G., Olshevsky, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pesek, M., Peshekhonov, D. V., Peskova, M., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Quaresma, M., Quintans, C., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rychter, A., Rymbekova, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savada, T., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sharko, K., Sinha, L., Spulbeck, D., Srnka, A., Stolarski, M., Sulc, M., Suzuki, H., Tessaro, S., Tessarotto, F., Thiel, A., Tosello, F., Townsend, A., Triloki, T., Tskhay, V., Valinoti, B., Veit, B. M., Veloso, J. F. C. A., Ventura, B., Vijayakumar, A., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: The COMPASS Collaboration performed measurements of the Drell-Yan process in 2015 and 2018 using a 190 GeV/c $\pi^{-}$ beam impinging on a transversely polarised ammonia target. Combining the data of both years, we present final results on the amplitudes of the five azimuthal modulations in the dimuon production cross section. Three of these transverse-spin-dependent azimuthal asymmetries (TSAs) probe the nucleon leading-twist Sivers, transversity, and pretzelosity transverse-momentum dependent (TMD) parton distribution functions (PDFs). The other two are induced by subleading effects. These TSAs provide unique new inputs for the study of the nucleon TMD PDFs and their universality properties. In particular, the Sivers TSA observed in this measurement is consistent with the fundamental QCD prediction of a sign change of naive time-reversal-odd TMD PDFs when comparing the Drell-Yan process with semi-inclusive measurements of deep inelastic scattering. Also, within the context of model predictions, the observed transversity TSA is consistent with the expectation of a sign change for the Boer-Mulders function.
Published: 2023

11. Observation of $K^{+} \to \pi^{+}\pi^{0}\pi^{0}\gamma$ decay

Author: Filippov, S. N., Gushchin, E. N., Khudyakov, A. A., Kravtsov, V. I., Kudenko, Yu G., Kulik, A. V., Polyarush, A. Yu., Artamonov, A. V., Donskov, S. V., Filin, A. P., Gorin, A. M., Inyakin, A. V., Khaustov, G. V., Kholodenko, S. A., Kolosov, V. N., Kurshetsov, V. F., Lishin, V. A., Medynsky, M. V., Obraztsov, V. F., Okhotnikov, A. V., Polyakov, V. A., Romanovsky, V. I., Rykalin, V. I., Sadovsky, A. S., Samoylenko, V. D., Tiurin, I. S., Uvarov, V. A., Yushchenko, O. P., Bychkov, V. N., Kekelidze, G. D., Lysan, V. M., and Zalikhanov, B. Zh.
Subjects: High Energy Physics - Experiment
Abstract: The $K^{+} \to \pi^{+}\pi^{0}\pi^{0}\gamma$ decay is observed by the OKA collaboration. The branching ratio is measured to be $(4.1 \pm 0.9(stat) \pm 0.4(syst))\times 10^{-6}$. The branching ratio and $\gamma$ energy spectrum are consistent with ChPT prediction., Comment: arXiv admin note: text overlap with arXiv:2310.16429
Published: 2023

12. Searches for the light invisible axion-like particle in $K^{+}\to\pi^{+}\pi^{0}a$ decay

Author: Sadovsky, A. S., Filin, A. P., Akimenko, S. A., Artamonov, A. V., Blik, A. M., Donskov, S. V., Gorin, A. M., Inyakin, A. V., Khaustov, G. V., Kholodenko, S. A., Kolosov, V. N., Kurshetsov, V. F., Lishin, V. A., Medynsky, M. V., Obraztsov, V. F., Okhotnikov, A. V., Polyakov, V. A., Romanovsky, V. I., Rykalin, V. I., Samoylenko, V. D., Tiurin, I. S., Uvarov, V. A., Yushchenko, O. P., Filippov, S. N., Gushchin, E. N., Khudyakov, A. A., Kravtsov, V. I., Kudenko, Yu G., Kulik, A. V., Polyarush, A. Yu., Bychkov, V. N., Kekelidze, G. D., Lysan, V. M., and Zalikhanov, B. Zh.
Subjects: High Energy Physics - Experiment
Abstract: A high statistics data sample of the $K^{+}$ decays is recorded by the OKA collaboration. A missing mass analysis is performed to search for a light invisible pseudoscalar axion-like particle (ALP) $a$ in the decay $K^{+} \to \pi^{+} \pi^{0} a$. No signal is observed, the upper limits for the branching ratio of the decay are calculated. The $90\%$ confidence level upper limit is changing from $2.5\cdot10^{-6}$ to $2\cdot10^{-7}$ for the ALP mass from 0 to 200 MeV/$c^{2}$, except for the region of $\pi^{0}$ mass, where the upper limit is $4.4\cdot10^{-6}$., Comment: 6 pages, 6 figures
Published: 2023
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13. Probing Light Dark Matter with positron beams at NA64

Author: Andreev, Yu. M., Antonov, A., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Bondi, M., Celentano, A., Charitonidis, N., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Kachanov, V. A., Kambar, Y., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Gertsenberger, S. V., Kasianova, E. A., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marini, A., Marsican, L., Matveev, V. A., Fredes, R. M., Yanssen, R. M., Mikhailov, Yu. V., Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Salamatin, K., Samoylenko, V. D., Sieber, H., Shchukin, D., Soto, O., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Tuzi, M., Ulloa, P., Volkov, P. V., Volkov, V. Yu., Voronchikhin, I. V., Zamora-Saa, J., and Zhevlakov, A. S.
Subjects: High Energy Physics - Experiment
Abstract: We present the results of a missing-energy search for Light Dark Matter which has a new interaction with ordinary matter transmitted by a vector boson, called dark photon $A^\prime$. For the first time, this search is performed with a positron beam by using the significantly enhanced production of $A^\prime$ in the resonant annihilation of positrons with atomic electrons of the target nuclei, followed by the invisible decay of $A^\prime$ into dark matter. No events were found in the signal region with $(10.1 \pm 0.1)~\times~10^{9}$ positrons on target with 100 GeV energy. This allowed us to set new exclusion limits that, relative to the collected statistics, prove the power of this experimental technique. This measurement is a crucial first step toward a future exploration program with positron beams, whose estimated sensitivity is here presented., Comment: Version submitted to PRL
Published: 2023

14. Search for Light Dark Matter with NA64 at CERN

Author: Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Silva, R. B. Galleguillos, Gardikiotis, A., Gertsenberger, S. V., Girod, S., Gninenko, S. N., H"osgen, M., Kachanov, V. A., Kambar, Y., Karneyeu, A. E., Kasianova, E. A., Kekelidze, G. D., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marini, A., Marsicano, L., Matveev, V. A., Fredes, R. Mena, Yanssen, R. G. Mena, Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Salamatin, K. M., Samoylenko, V. D., Sieber, H., Shchukin, D., Soto, O., Tikhomirov, V. O., Tlisova, I. V., Toropin, A. N., Trifonov, A. Yu., Tuzi, M., Vasilishin, B. I., Volkov, P. V., Volkov, V. Yu., Voronchikhin, I. V., Zamora-Saa, J., and Zhevlakov, A. S.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: Thermal dark matter models with particle $\chi$ masses below the electroweak scale can provide an explanation for the observed relic dark matter density. This would imply the existence of a new feeble interaction between the dark and ordinary matter. We report on a new search for the sub-GeV $\chi$ production through the interaction mediated by a new vector boson, called the dark photon $A'$, in collisions of 100 GeV electrons with the active target of the NA64 experiment at the CERN SPS. With $9.37\times10^{11}$ electrons on target collected during 2016-2022 runs NA64 probes for the first time the well-motivated region of parameter space of benchmark thermal scalar and fermionic dark matter models. No evidence for dark matter production has been found. This allows us to set the most sensitive limits on the $A'$ couplings to photons for masses $m_{A'} \lesssim 0.35$ GeV, and to exclude scalar and Majorana dark matter with the $\chi-A'$ coupling $\alpha_D \leq 0.1$ for masses $0.001 \lesssim m_\chi \lesssim 0.1$ GeV and $3m_\chi \leq m_{A'}$., Comment: 7 pages, 7 figures. arXiv admin note: text overlap with arXiv:1906.00176
Published: 2023

15. Measurement of the intrinsic hadronic contamination in the NA64$-e$ high-purity $e^+/e^-$ beam at CERN

Author: Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Bondi, M., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., H"osgen, M., Jeckel, M., Kachanov, V. A., Kambar, Y., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Gertsenberger, S. V., Kasianova, E. A., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marini, A., Marsicano, L., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Salamatin, K., Samoylenko, V. D., Sieber, H., Shchukin, D., Soto, O., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Tuzi, M., Ulloa, P., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Voronchikhin, I. V., Zamora-Sa'a, J., and Zhevlakov, A. S.
Subjects: High Energy Physics - Experiment, Physics - Accelerator Physics
Abstract: In this study, we present the measurement of the intrinsic hadronic contamination at the CERN SPS H4 beamline configured to transport electrons and positrons at 100 GeV/c momentum. The analysis was performed using data collected by the NA64-$e$ experiment in 2022. Our study is based on calorimetric measurements, exploiting the different interaction mechanisms of electrons and hadrons in the NA64-ECAL and NA64-HCAL detectors. We determined the intrinsic hadronic contamination by comparing the results obtained using the nominal electron/positron beamline configuration with those obtained in a dedicated setup, in which only hadrons impinged on the detector. The significant differences in the experimental signatures of electrons and hadrons motivated our approach, resulting in a small and well-controlled systematic uncertainty for the measurement. Our study allowed us to precisely determine the intrinsic hadronic contamination, which represents a crucial parameter for the NA64 experiment in which the hadron contaminants may result in non-trivial backgrounds. Moreover, we performed dedicated Monte Carlo simulations for the hadron production induced by the primary T2 target. We found a good agreement between measurements and simulation results, confirming the validity of the applied methodology and our evaluation of the intrinsic hadronic contamination.
Published: 2023

16. The LHCb upgrade I

Author: LHCb collaboration, Aaij, R., Abdelmotteleb, A. S. W., Beteta, C. Abellan, Abudinén, F., Achard, C., Ackernley, T., Adeva, B., Adinolfi, M., Adlarson, P., Afsharnia, H., Agapopoulou, C., Aidala, C. A., Ajaltouni, Z., Akar, S., Akiba, K., Albicocco, P., Albrecht, J., Alessio, F., Alexander, M., Albero, A. Alfonso, Aliouche, Z., Cartelle, P. Alvarez, Amalric, R., Amato, S., Amey, J. L., Amhis, Y., An, L., Anderlini, L., Andersson, M., Andreani, A., Andreianov, A., Andreotti, M., Andreou, D., Andrews, J. E., Anelli, M., Anjam, A., Ao, D., Archilli, F., Arnaud, K., Artamonov, A., Artuso, M., Ashby, J., Aslanides, E., Atzeni, M., Audurier, B., Rocha, D. Ayres, Perea, I. B Bachiller, Bachmann, S., Bachmayer, M., Back, J. J., Bailly-reyre, A., Rodriguez, P. Baladron, Balagura, V., Balbi, G., Baldini, W., Balla, A., Baltazar, M., Band, H., Leite, J. Baptista de Souza, Barbetti, M., Barclay, P., Barlow, R. J., Barsuk, S., Barter, W., Bartolini, M., Baryshnikov, F., Basels, J. M., Bassi, G., Baszczyk, M., Lopes, J. C. Batista, Batsukh, B., Battig, A., Bay, A., Beck, A., Becker, M., Bedeschi, F., Bediaga, I. B., Beigbeder-Beau, C., Beiter, A., Belin, S., Bellee, V., Belous, K., Belov, I., Belyaev, I., Benane, G., Bencivenni, G., Benettoni, M., Ben-Haim, E., Berezhnoy, A., Bernard, F., Bernet, R., Andres, S. Bernet, Berninghoff, D., Bernstein, H. C., Bertella, C., Bertolin, A., Betancourt, C., Betti, F., Bezshyiko, Ia., Bezshyyko, O., Bhasin, S., Bhom, J., Bian, L., Bieker, M. S., Biesuz, N. V., Billoir, P., Biolchini, A., Birch, M., Bishop, F. C. R., Bitadze, A., Bizzeti, A., Blago, M. P., Blake, T., Blanc, F., Blank, J. E., Blusk, S., Bobulska, D., Bochin, B., Boelhauve, J. A., Garcia, O. Boente, Boettcher, T., Bogdanova, G., Boiaryntseva, I., Boldyrev, A., Bolognani, C. S., Bolzonella, R., Bondar, N., Booth, M. J., Borgato, F., Borghi, S., Borsato, M., Borsuk, J. T., Boterenbrood, H., Bouchiba, S. A., Bowcock, T. J. V., Boyaryntsev, A., Boyer, A., Bozzi, C., Bradley, M. J., Braun, S., Rodriguez, A. Brea, Bregliozzi, G., Bridges, K., Briere, M. M. J., Brock, M., Brodski, M., Brodzicka, J., Gonzalo, A. Brossa, Brown, C., Brown, J., Brummitt, A. J., Brundu, D., Brunetti, L., Buda, L., Buonaura, A., Buonincontri, L., Burke, A. T., Burmistrov, L., Burr, C., Bursche, A., Butkevich, A., Butter, J. S., Buytaert, J., Byczynski, W., Cachemiche, J. P., Cadeddu, S., Cai, H., Caillet, A., Calabrese, R., Calefice, L., Calegari, D., Cali, S., Calvi, M., Gomez, M. Calvo, Campana, P., Perez, D. H. Campora, Quezada, A. F. Campoverde, Canfer, S., Capelli, S., Capriotti, L., Carassiti, V., Carbone, A., Cardinale, R., Cardini, A., Carletti, M., Carniti, P., Carroll, J., Carus, L., Vidal, A. Casais, Caspary, R., Casse, G., Cattaneo, M., Cavallero, G., Cavallini, V., Ceelie, L., Celani, S., Cerasoli, J., Cervenkov, D., Cesare, S., Chadaj, B., Chadwick, A. J., Chahrour, I., Chanal, H., Chapman, M. G., Charles, M., Charpentier, Ph., Chaumat, V. J., Barajas, C. A. Chavez, Chefdeville, M., Chen, C., Chen, S., Chernov, A., Chernov, E., Chernyshenko, S., Chiozzi, S., Chobanova, V., Cholak, S., Chrzaszcz, M., Chubykin, A., Chulikov, V., Ciambrone, P., Cicala, M. F., Vidal, X. Cid, Ciezarek, G., Cifra, P., Citterio, M., Ciullo, G., Clark, K., Clarke, P. E. L., Clemencic, M., Cliff, H. V., Closier, J., Cobbledick, J. L., Coco, V., Coelli, S., Cogan, J., Cogneras, E., Cojocariu, L., Collins, P., Colombo, T., Congedo, L., Conti, N., Contu, A., Cooke, N., Corredoira, I., Corti, G., Ramusino, A. Cotta, Couturier, B., Cowan, G. A., Craik, D. C., Torres, M. Cruz, Currie, R., Da Silva, C. L., Dadabaev, S., Dai, L., Dai, X., Dall'Occo, E., Dalseno, J., D'Ambrosio, C., Damen, A., Daniel, J., Danilina, A., d'Argent, P., Daudon, F., Davies, J. E., Davis, A., Davis, J., Francisco, O. De Aguiar, De Benedetti, F., de Boer, J., De Bruyn, K., De Capua, S., De Cian, M., Da Graca, U. 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K., Websdale, D., Webster, J., Wei, Y., Westhenry, B. D. C., White, D. J., Whitehead, M., Wieczorek, D., Wiederhold, A. R., Wiedner, D., Wilkinson, G., Wilkinson, M. K., Williams, I., Williams, M., Williams, M. R. J., Williams, R., Wilson, F. F., Wimberley, J., Windelband, B., Wislicki, W., Witek, M., Witola, L., Wlochal, M., Wong, C. P., Wormald, M., Wormser, G., Wotton, S. A., Wraight, K., Wu, H., Wu, J., Wyllie, K., Xiang, Z., Xie, Y., Xu, A., Xu, J., Xu, L., Xu, M., Xu, Q., Xu, Z., Yang, D., Yang, S., Yang, X., Yang, Y., Yang, Z., Yeomans, L. E., Yeroshenko, V., Yeung, H., Yin, H., Yu, J., Yuan, X., Zaffaroni, E., Zavertyaev, M., Zdybal, M., Zenaiev, O., Zeng, M., Zhang, C., Zhang, D., Zhang, L., Zhang, S., Zhang, Y., Zhao, Y., Zharkova, A., Zhelezov, A., Zheng, Y., Zhou, T., Zhou, X., Zhou, Y., Zhovkovska, V., Zhu, X., Zhu, Z., Zhukov, V., Zivkovic, V., Zou, Q., Zucchelli, S., Zuliani, D., Zunica, G., and Zvyagintsev, S.
Subjects: High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract: The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software., Comment: All figures and tables, along with any supplementary material and additional information, are available at http://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-DP-2022-002.html (LHCb public pages)
Published: 2023
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17. Collins and Sivers transverse-spin asymmetries in inclusive muoproduction of $\rho^0$ mesons

Author: Alexeev, G. D., Alexeev, M. G., Alice, C., Amoroso, A., Andrieux, V., Anosov, V., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Del Carro, F., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Dünnweber, W., Dusaev, R. R., Ecker, D., Efremov, A., Elia, C., Eremeev, D., Faccioli, P., Faessler, M., Finger, M., Finger jr., M., Fischer, H., Flöthner, K. J., Florian, W., Friedrich, J. M., Frolov, V., Ordòñez, L. G. Garcia, Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, D., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Grüner, M., Guskov, A., von Harrach, D., Hoffmann, M., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, V., Joosten, R., Kabuß, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khatun, A., Khaustov, G. V., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Horikawa, K. Kondo, Konorov, I., Konstantinov, V. F., Korzenev, A. M., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Martin, A., Marzec, J., Matoušek, J., Matsuda, T., Mattson, G., Pires, C. Menezes, Metzger, F., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Miura, D., Miyachi, Y., Molina, R., Moretti, A., Nagaytsev, A., Naim, C., Neyret, D., Nový, J., Nowak, W. -D., Nukazuka, G., Olshevsky, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pešek, M., Peshekhonov, D. V., Pešková, M., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Quaresma, M., Quintans, C., Reicherz, G., Riedl, C., Rudnicki, T., Ryabchikov, D. I., Rychter, A., Rymbekova, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sharko, K., Sinha, L., Slunecka, M., Sozzi, F., Spülbeck, D., Srnka, A., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Townsend, A., Triloki, T., Tskhay, V., Valinoti, B., Veit, B. M., Veloso, J. F. C. A., Ventura, B., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: The production of vector mesons in deep inelastic scattering is an interesting yet scarsely explored channel to study the transverse spin structure of the nucleon and the related phenomena. The COMPASS collaboration has performed the first measurement of the Collins and Sivers asymmetries for inclusively produced $\rho^0$ mesons. The analysis is based on the data set collected in deep inelastic scattering in $2010$ using a $160\,\,\rm{GeV}/c$ $\mu^+$ beam impinging on a transversely polarized $\rm{NH}_3$ target. The $\rho^{0}$ mesons are selected from oppositely charged hadron pairs, and the asymmetries are extracted as a function of the Bjorken-$x$ variable, the transverse momentum of the pair and the fraction of the energy $z$ carried by the pair. Indications for positive Collins and Sivers asymmetries are observed.
Published: 2022
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18. Spin Density Matrix Elements in Exclusive $\rho ^0$ Meson Muoproduction

Author: Alexeev, G. D., Alexeev, M. G., Alice, C., Amoroso, A., Andrieux, V., Anosov, V., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Del Carro, F., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Dünnweber, W., Dusaev, R. R., Ecker, D., Efremov, A., Eremeev, D., Faccioli, P., Faessler, M., Finger, M., Finger jr., M., Fischer, H., Flöthner, K. J., Florian, W., Friedrich, J. M., Frolov, V., Ordòñez, L. G. Garcia, Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, D., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Grüner, M., Guskov, A., von Harrach, D., Hoffmann, M., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, V., Joosten, R., Kabuß, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khatun, A., Khaustov, G. V., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Horikawa, K. Kondo, Konorov, I., Konstantinov, V. F., Korzenev, A. M., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Martin, A., Marzec, J., Matoušek, J., Matsuda, T., Mattson, G., Pires, C. Menezes, Metzger, F., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Miura, D., Miyachi, Y., Molina, R., Moretti, A., Nagaytsev, A., Naim, C., Neyret, D., Niemiec, M., Nový, J., Nowak, W. -D., Nukazuka, G., Olshevsky, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pešek, M., Peshekhonov, D. V., Pešková, M., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Quaresma, M., Quintans, C., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rychter, A., Rymbekova, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sharko, K., Sinha, L., Slunecka, M., Spülbeck, D., Srnka, A., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Townsend, A., Triloki, T., Tskhay, V., Valinoti, B., Veit, B. M., Veloso, J. F. C. A., Ventura, B., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive $\rho ^0$ meson muoproduction at COMPASS using 160~GeV/$c$ polarised $ \mu ^{+}$ and $ \mu ^{-}$ beams impinging on a liquid hydrogen target. The measurement covers the kinematic range 5.0~GeV/$c^2$ $< W <$ 17.0~GeV/$c^2$, 1.0 (GeV/$c$)$^2$ $< Q^2 <$ 10.0 (GeV/$c$)$^2$ and 0.01 (GeV/$c$)$^2$ $< p_{\rm{T}}^2 <$ 0.5 (GeV/$c$)$^2$. Here, $W$ denotes the mass of the final hadronic system, $Q^2$ the virtuality of the exchanged photon, and $p_{\rm{T}}$ the transverse momentum of the $\rho ^0$ meson with respect to the virtual-photon direction. The measured non-zero SDMEs for the transitions of transversely polarised virtual photons to longitudinally polarised vector mesons ($\gamma^*_T \to V^{ }_L$) indicate a violation of $s$-channel helicity conservation. Additionally, we observe a dominant contribution of natural-parity-exchange transitions and a very small contribution of unnatural-parity-exchange transitions, which is compatible with zero within experimental uncertainties. The results provide important input for modelling Generalised Parton Distributions (GPDs). In particular, they may allow one to evaluate in a model-dependent way the role of parton helicity-flip GPDs in exclusive $\rho ^0$ production.
Published: 2022

19. Measurement of T-odd asymmetry in radiative K+ -> pi0 e+ nu gamma decay using OKA detector

Author: Polyarush, A. Yu., Akimenko, S. A., Artamonov, A. V., Bychkov, V. N., Donskov, S. V., Duka, V. A., Inyakin, A. V., Gorin, A. M., Gushchin, E. N., Filin, A. P., Filippov, S. N., Kekelidze, G. D., Kolosov, V. N., Kravtsov, V. I., Khaustov, G. V., Kholodenko, S. A., Khudyakov, A. A., Kudenko, Yu. G., Kulik, A. V., Kurshetsov, V. F., Lishin, V. A., Lysan, V. M., Medynsky, M. V., Obraztsov, V. F., Ohotnikov, A. V., Polyakov, V. A., Romanovsky, V. I., Rykalin, V. I., Sadovsky, A. S., Samoilenko, V. D., Tyurin, I. S., Tchikilev, O. G., Uvarov, V. A., Yushchenko, O. P., and Zalikhanov, B. Zh.
Subjects: High Energy Physics - Experiment
Abstract: The paper presents a measurement of the T-odd correlation in radiation decay \boldmath $K^+ \rightarrow \pi^{0} e^{+} \nu_{e} \gamma $ performed on the installation of the 101200 candidate events of the investigated decay were identified. Measured correlation $\xi_{\pi e \gamma}$ -is a mixed product of moments $e^{+}$, $\pi^{0}$, $\gamma$ in the kaon rest system, normalized by $M^{3}_{K}$. To assess the asymmetry of the distribution by $\xi_{\pi e \gamma}$ the value used is $A_{\xi}= \frac {N_{+}-N_{-}} {N_{+}+N_{-}}$, where $N_{+(-)}$ is the number of events with $\xi$ greater than (less than) zero. For the $A_{\xi}$ asymmetry, the value is obtained $A_{\xi} = (+0.1 \pm 3.9($stat.$) \pm1.7($syst.$))\times10^{-3}$ or $|A_{\xi}| < 5.4\times10^{-3} (90\%~ CL)$
Published: 2022
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20. Search for a New B-L Z' Gauge Boson with the NA64 Experiment at CERN

Author: Andreev, Yu. M., Banerjee, D., Banto-Oberhauser, B., Bernhard, J., Bisio, P., Bondi, M., Burtsev, V., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G. D., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marsicano, L., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Salamatin, K., Samoylenko, V. D., Sieber, H., Shchukin, D., Soto, O., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Vasilishin, B. I., Volkov, P. V., Volkov, V. Yu., Voronchikhin, I., and Zamora-Saa, J.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: A search for a new $Z'$ gauge boson associated with (un)broken B-L symmetry in the keV-GeV mass range is carried out for the first time using the missing-energy technique in the NA64 experiment at the CERN SPS. From the analysis of the data with 3.22e11 electrons on target collected during 2016-2021 runs no signal events were found. This allows to derive new constraints on the $Z'-e$ coupling strength, which for the mass range $0.3 < m_{Z'} < 100$ MeV are more stringent compared to those obtained from the neutrino-electron scattering data., Comment: 6 pages, 3 figures. Revised shorter version, Fig.3 updated, published in Physical Review Letters
Published: 2022
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21. Search for a light muon-philic $Z^\prime$ with the NA64-$e$ experiment at CERN

Author: Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Bondì, M., Burtsev, V. E., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hösgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marsicano, L., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Salamatin, K. M., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu, Ulloa, P., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Voronchikhin, I.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: The extension of Standard Model made by inclusion of additional $U(1)$ gauge $L_\mu-L_\tau$ symmetry can explain the difference between the measured and the predicted value of the muon magnetic moment and solve the tension in $B$ meson decays. This model predicts the existence of a new, light $Z^\prime$ vector boson, predominantly coupled to second and third generation leptons, whose interaction with electrons is due to a loop mechanism involving muons and taus. In this work, we present a rigorous evaluation of the upper limits in the $Z^\prime$ parameter space, obtained from the analysis of the data collected by the NA64-$e$ experiment at CERN SPS, that performed a search for light dark matter with $2.84\times10^{11}$ electrons impinging with 100 GeV on an active thick target. The resulting limits, despite being included in a region already investigated by neutrino experiments,touch the muon $g-2$ preferred band for values of the $Z^\prime$ mass of order of 1 MeV. The sensitivity projections for the future high-statistics NA64-$e$ runs demonstrate the power of the electrons/positron beam approach in this theoretical scenario., Comment: 11 pages, 9 figures. This version was accepted for publication
Published: 2022
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22. Double $J/\psi$ production in pion-nucleon scattering at COMPASS

Author: Alexeev, G. D., Alexeev, M. G., Amoroso, A., Andrieux, V., Anosov, V., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Ball, M., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Efremov, A., Eremeev, D., Eversheim, P. D., Faccioli, P., Faessler, M., Finger, M., Finger jr., M., Fischer, H., Floethner, K., Florian, W, Franco, C., Friedrich, J. M., Frolov, V., Ordonez, L. G. Garcia, Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, D., Gorzellik, M., Grasso, A., Gridin, A., Groote, S., Perdekamp, M. Grosse, Grube, B., Gruener, M., Guskov, A., von Harrach, D., Hoffmann, M., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khatun, A., Khaustov, G. V., Khokhlov, Yu. A., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Horikawa, K. Kondo, Konorov, I., Konstantinov, V. F., Korzenev, A., Koshkarev, S., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Mattson, G., Pires, C. Menezes, Metzger, F., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Miyachi, Y., Molina, R., Moretti, A., Nagaytsev, A., Naim, C., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Olshevsky, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pesek, M., Peshekhonov, D. V., Peskova, M., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Reicherz, G., Riedl, C., Rudnicki, T., Ryabchikov, D. I., Rychter, A., Rymbekova, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmeing, S., Schmieden, H., Selyunin, A., Sharko, K., Sinha, L., Slunecka, M., Spuelbeck, D., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Townsend, A., Triloki, T., Tskhaty, V., Valinoti, B., Veit, B. M., Veloso, J. F. C. A., Ventura, B., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We present the study of the production of double $J/\psi$ mesons using COMPASS data collected with a 190 GeV/$c$ $\pi^-$ beam scattering off NH$_{3}$, Al and W targets. Kinematic distributions of the collected double $J/\psi$ events are analysed, and the double $J/\psi$ production cross section is estimated for each of the COMPASS targets. The results are compared to predictions from single- and double-parton scattering models as well as the pion intrinsic charm and the tetraquark exotic resonance hypotheses. It is demonstrated that the single parton scattering production mechanism gives the dominant contribution that is sufficient to describe the data. An upper limit on the double intrinsic charm content of pion is evaluated. No significant signatures that could be associated with exotic tetraquarks are found in the double $J/\psi$ mass spectrum., Comment: 12 pages, 4 figures
Published: 2022
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23. Improved exclusion limit for light dark matter from $e^+e^-$ annihilation in NA64

Author: Andreev, Yu., Banerjee, D., Bernhard, J., Bondi, M., Burtsev, V., Celentano, A., Charitonidis, N., Chumakov, A., Cooke, D., Crivelli, P., Depero, E., Dermenev, A., Donskov, S., Dusaev, R., Enik, T., Feshchenko, A., Frolov, V., Gardikiotis, A., Gerassimov, S., Gninenko, S., Hoesgen, M., Jeckel, M., Kachanov, V., Karneyeu, A., Kekelidze, G., Ketzer, B., Kirpichnikov, D., Kirsanov, M., Kolosov, V., Konorov, I., Kovalenko, S., Kramarenko, V., Kravchuk, L., Krasnikov, N., Kuleshov, S., Lyubovitskij, V., Lysan, V., Marsicano, L., Matveev, V., Mikhailov, Yu., Molina, L., Peshekhonov, D., Polyakov, V., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V., Sieber, H., Shchukin, D., Tikhomirov, V., Tlisova, I., Toropin, A., Trifonov, A., Ulloa, P., Vasilishin, B., Vasquez, G., Volkov, P., and Volkov, V.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: The current most stringent constraints for the existence of sub-GeV dark matter coupling to Standard Model via a massive vector boson $A^\prime$ were set by the NA64 experiment for the mass region $m_{A^\prime}\lesssim 250$ MeV, by analyzing data from the interaction of $2.84\cdot10^{11}$ 100-GeV electrons with an active thick target and searching for missing-energy events. In this work, by including $A^\prime$ production via secondary positron annihilation with atomic electrons, we extend these limits in the $200$-$300$ MeV region by almost an order of magnitude, touching for the first time the dark matter relic density constrained parameter combinations. Our new results demonstrate the power of the resonant annihilation process in missing energy dark-matter searches, paving the road to future dedicated $e^+$ beam efforts., Comment: Version accepted for publication as a Letter in Phys. Rev. D
Published: 2021
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24. The exotic meson $\pi_1(1600)$ with $J^{PC} = 1^{-+}$ and its decay into $\rho(770)\pi$

Author: Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anosov, V., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Antequera, J. Berenguer, Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Efremov, A., Eremeev, D., Eversheim, P. D., Faccioli, P., Faessler, M., Finger, M., Finger jr., M., Fischer, H., Floethner, K., Franco, C., Friedrich, J. M., Frolov, V., Ordonez, L. G. Garcia, Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, D., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Guskov, A., Haas, F., von Harrach, D., Hoffmann, M., Heitz, R., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Mattson, G., Metzger, F., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Miyachi, Y., Moretti, A., Nagaytsev, A., Naim, C., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Olshevsky, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pesek, M., Peshekhonov, D. V., Peskova, M., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Reicherz, G., Riedl, C., Rudnicki, T., Ryabchikov, D. I., Rymbekova, A., Rychter, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmeing, S., Schmieden, H., Selyunin, A., Sharko, K., Sinha, L., Slunecka, M., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Townsend, A., Tskhay, V., Triloki, T., Uhl, S., Vauth, A., Veit, B. M., Veloso, J., Ventura, B., Vidon, A., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., Zhao, Y., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We study the spin-exotic $J^{PC} = 1^{-+}$ amplitude in single-diffractive dissociation of 190 GeV$/c$ pions into $\pi^-\pi^-\pi^+$ using a hydrogen target and confirm the $\pi_1(1600) \to \rho(770) \pi$ amplitude, which interferes with a nonresonant $1^{-+}$ amplitude. We demonstrate that conflicting conclusions from previous studies on these amplitudes can be attributed to different analysis models and different treatment of the dependence of the amplitudes on the squared four-momentum transfer and we thus reconcile their experimental findings. We study the nonresonant contributions to the $\pi^-\pi^-\pi^+$ final state using pseudo-data generated on the basis of a Deck model. Subjecting pseudo-data and real data to the same partial-wave analysis, we find good agreement concerning the spectral shape and its dependence on the squared four-momentum transfer for the $J^{PC} = 1^{-+}$ amplitude and also for amplitudes with other $J^{PC}$ quantum numbers. We investigate for the first time the amplitude of the $\pi^-\pi^+$ subsystem with $J^{PC} = 1^{--}$ in the $3\pi$ amplitude with $J^{PC} = 1^{-+}$ employing the novel freed-isobar analysis scheme. We reveal this $\pi^-\pi^+$ amplitude to be dominated by the $\rho(770)$ for both the $\pi_1(1600)$ and the nonresonant contribution. We determine the $\rho(770)$ resonance parameters within the three-pion final state. These findings largely confirm the underlying assumptions for the isobar model used in all previous partial-wave analyses addressing the $J^{PC} = 1^{-+}$ amplitude.
Published: 2021
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25. Probing the explanation of the muon (g-2) anomaly and thermal light dark matter with the semi-visible dark photon channel

Author: Cazzaniga, C., Odagiu, P., Depero, E., Bueno, L. Molina, Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Girod, S., Gninenko, S. N., Hösgen, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Sieber, H., Tikhomirov, V. O., Tlisova, I. V., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We report the results of a search for a new vector boson ($A'$) decaying into two dark matter particles $\chi_1 \chi_2$ of different mass. The heavier $\chi_2$ particle subsequently decays to $\chi_1$ and $A' \to e^- e^+$. For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay $A'\to \chi \overline{\chi}$ and axion-like or pseudo-scalar particles $a \to \gamma \gamma$. With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for $A'$ masses from 2$m_e$ up to 390 MeV and mixing parameter $\epsilon$ between $3\times10^{-5}$ and $2\times10^{-2}$.
Published: 2021
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26. Probing transversity by measuring $\Lambda$ polarisation in SIDIS

Author: Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anosov, V., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Antequera, J. Berenguer, Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Efremov, A., Eversheim, P. D., Faccioli, P., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., Friedrich, J. M., Frolov, V., Ordonez, L. G. Garcia, Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Giordano, D., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Guskov, A., von Harrach, D., Heitz, R., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Kabuss, E., Kang, D. H., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Mattson, G., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Miyachi, Y., Moretti, A., Nagaytsev, A., Naim, C., Negrini, T. S., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevskiy, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pesek, M., Peshekhonov, D. V., Peskova, M., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Reicherz, G., Riedl, C., Rudnicki, T., Ryabchikov, D. I., Rymbekova, A., Rychter, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schiavon, P., Schmieden, H., Selyunin, A., Sharko, K., Sinha, L., Slunecka, M., Smolik, J., Sozzi, F., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Sznajder, P., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Townsend, A., Tskhay, V., Uhl, S., Vauth, A., Veit, B. M., Veloso, J., Ventura, B., Vidon, A., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavada, P., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., Zhao, Y., and Ziembicki, M.
Subjects: High Energy Physics - Experiment
Abstract: Based on the observation of sizeable target-transverse-spin asymmetries in single-hadron and hadron-pair production in Semi-Inclusive measurements of Deep Inelastic Scattering (SIDIS), the chiral-odd transversity quark distribution functions $h_1^q$ are nowadays well established. Several possible channels to access these functions were originally proposed. One candidate is the measurement of the polarisation of $\Lambda$ hyperons produced in SIDIS off transversely polarised nucleons, where the transverse polarisation of the struck quark might be transferred to the final-state hyperon. In this article, we present the COMPASS results on the transversity-induced polarisation of $\Lambda$ and $\bar{\Lambda}$ hyperons produced in SIDIS off transversely polarised protons. Within the experimental uncertainties, no significant deviation from zero was observed. The results are discussed in the context of different models taking into account previous experimental results on $h_1^u$ and $h_1^d$., Comment: 18 pages, 6 figures
Published: 2021
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27. Search for pseudoscalar bosons decaying into $e^+e^-$ pairs in the NA64 experiment at the CERN SPS

Author: Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Subjects: High Energy Physics - Experiment
Abstract: We report the results of a search for a light pseudoscalar particle $a$ that couples to electrons and decays to $e^+e^-$ performed using the high-energy CERN SPS H4 electron beam. If such pseudoscalar with a mass $\simeq 17$ MeV exists, it could explain the ATOMKI anomaly. We used the NA64 data samples collected in the "visible mode" configuration with total statistics corresponding to $8.4\times 10^{10}$ electrons on target (EOT) in 2017 and 2018. In order to increase sensitivity to small coupling parameter $\epsilon$ we used also the data collected in 2016-2018 in the "invisible mode" configuration of NA64 with a total statistics corresponding to $2.84\times 10^{11}$ EOT. A thorough analysis of both these data samples in the sense of background and efficiency estimations was already performed and reported in our previous papers devoted to the search for light vector particles and axion-like particles (ALP). In this work we recalculate the signal yields, which are different due to different cross section and life time of a pseudoscalar particle $a$, and perform a new statistical analysis. As a result, the region of the two dimensional parameter space $m_a - \epsilon$ in the mass range from 1 to 17.1 MeV is excluded. At the mass of the ATOMKI anomaly the values of $\epsilon$ in the range $2.1 \times 10^{-4} < \epsilon < 3.2 \times 10^{-4}$ are excluded., Comment: 6 pages, 2 figures
Published: 2021
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28. Constraints on New Physics in the Electron g-2 from a Search for Invisible Decays of a Scalar, Pseudoscalar, Vector, and Axial Vector

Author: Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Volkov, P. V., and Volkov, V. Yu.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We performed a search for a new generic $X$ boson, which could be a scalar ($S$), pseudoscalar ($P$), vector ($V$) or an axial vector ($A$) particle produced in the 100 GeV electron scattering off nuclei, $e^- Z \to e^- Z X$, followed by its invisible decay in the NA64 experiment at CERN. No evidence for such process was found in the full NA64 data set of $2.84\times 10^{11}$ electrons on target. We place new bounds on the $S, P, V, A$ coupling strengths to electrons, and set constraints on their contributions to the electron anomalous magnetic moment $a_e$, $|\Delta a_{X}| \lesssim 10^{-15} - 10^{-13}$ for the $X$ mass region $m_X\lesssim 1$ GeV. These results are an order of magnitude more sensitive compared to the current accuracy on $a_e$ from the electron $g-2$ experiments and recent high-precision determination of the fine structure constant., Comment: 6 pages, 4 figures
Published: 2021
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29. Study of $K^+ \rightarrow \pi^{0} e^{+} \nu \gamma $ decay with OKA setup

Author: Polyarush, A. Yu., Duk, V. A., Filippov, S. N., Guschin, E. N., Khudyakov, A. A., Kravtsov, V. I., Kudenko, Yu. G., Akimenko, S. A., Artamonov, A. V., Blik, A. M., Burtovoy, V. S., Donskov, S. V., Filin, A. P., Inyakin, A. V., Gorin, A. M., Khaustov, G. V., Kholodenko, S. A., Kolosov, V. N., Kurshetsov, V. F., Lishin, V. A., Medynsky, M. V., Mikhailov, Yu. V., Obraztsov, V. F., Polyakov, V. A., Romanovsky, V. I., Rykalin, V. I., Sadovsky, A. S., Samoilenko, V. D., Shapkin, M. M., Stenyakin, O. V., Tchikilev, O. G., Uvarov, V. A., Yushchenko, O. P., Bychkov, V. N., Kekelidze, G. D., Lysan, V. M., and Zalikhanov, B. Zh.
Subjects: High Energy Physics - Experiment
Abstract: Results of a study of the $K^+ \rightarrow \pi^{0} e^{+} \nu \gamma $ decay at OKA setup are presented. More than 32000 events of this decay are observed. The differential spectra over the photon energy and the photon-electron opening angle in kaon rest frame are presented. The branching ratios, normalized to that of $K_{e3}$ decay are calculated for different cuts in $E^*_\gamma$ and $cos\Theta^{*}_{e\gamma}$. In particular, the branching ratio for $E^{*}_{\gamma}>30$ MeV and $\Theta^{*}_{e \gamma}>20^{\circ}$ is measured R = $\frac{Br(K^+ \rightarrow \pi^{0} e^{+} \nu_{e} \gamma) } {Br(K^+ \rightarrow \pi^{0} e^{+} \nu_{e})} $ = =(0.587$\pm$0.010($stat.$)$\pm$0.015($syst.$))$\times10^{-2}$, which is in a good agreement with ChPT $O(p^{4})$ calculations.
Published: 2020
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30. Spin Density Matrix Elements in Exclusive $\omega$ Meson Muoproduction $^*$

Author: Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Antequera, J. Berenguer, Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Efremov, A., Eversheim, P. D., Faccioli, P., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., Friedrich, J. M., Frolov, V., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Guskov, A., von Harrach, D., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Joerg, P., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Horikawa, K. Kondo, Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Mattson, G., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Naim, C., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevskiy, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pesek, M., Peshekhonov, D. V., Peskova, M., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Regali, C., Reicherz, G., Riedl, C., Rudnicki, T., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sinha, L., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szameitat, T., Sznajder, P., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Townsend, A., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veit, B. M., Veloso, J., Ventura, B., Vidon, A., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavada, P., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., Zhao, Y., and Ziembicki, M.
Subjects: High Energy Physics - Experiment
Abstract: We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive $\omega$ meson muoproduction on the proton at COMPASS using 160 GeV/$c$ polarised $ \mu ^{+}$ and $ \mu ^{-}$ beams impinging on a liquid hydrogen target. The measurement covers the range 5.0 GeV/$c^2$ $< W <$ 17.0 GeV/$c^2$, with the average kinematics $\langle Q^{2} \rangle=$ 2.1 (GeV/$c$)$^2$, $\langle W \rangle= 7.6$ GeV/$c^2$, and $\langle p^{2}_{\rm T} \rangle = 0.16$ (GeV/$c$)$^2$. Here, $Q^2$ denotes the virtuality of the exchanged photon, $W$ the mass of the final hadronic system and $p_T$ the transverse momentum of the $\omega$ meson with respect to the virtual-photon direction. The measured non-zero SDMEs for the transitions of transversely polarised virtual photons to longitudinally polarised vector mesons ($\gamma^*_T \to V_L$) indicate a violation of $s$-channel helicity conservation. Additionally, we observe a sizeable contribution of unnatural-parity-exchange (UPE) transitions that decreases with increasing $W$. The results provide important input for modelling Generalised Parton Distributions (GPDs). In particular, they may allow to evaluate in a model-dependent way the contribution of UPE transitions and assess the role of parton helicity-flip GPDs in exclusive $\omega$ production., Comment: 31 pages, 12 figures, 1 appendix
Published: 2020
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31. Hunting down the X17 boson at the CERN SPS

Author: Depero, E., Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V., Chumakov, A ., Cooke, D., Dermenev, A., Donskov, S., Dusaev, R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V., Gardikiotis, A., Gerassimov, S., Girod, S., Gninenko, S., Hosgen, M., Kachanov, V., Karneyeu, A., Kekelidze, G., Ketzer, B., Kirpichnikov, D., Kirsanov, M., Kolosov, V., Konorov, I., Kovalenko, S., Kramarenko, V., Kravchuk, L., Krasnikov, N., Kuleshov, S., Lyubovitskij, V., Lysan, V., Matveev, V., Mikhailov, Yu., Bueno, L. Molina, Peshekhonov, D., Polyakov, V., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V., Shchukin, D., Sieber, H., Tikhomirov, V., Tlisova, I., Tlisov, D., Toropin, A., Trifonov, A., Vasilishin, B., Vasquez, G., Volkov, P., Volkov, V., Ulloa, P., and Crivelli, P.
Subjects: High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract: Recently, the ATOMKI experiment has reported new evidence for the excess of $e^+ e^-$ events with a mass $\sim$17 MeV in the nuclear transitions of $^4$He, that they previously observed in measurements with $^8$Be. These observations could be explained by the existence of a new vector $X17$ boson. So far, the search for the decay $X17 \rightarrow e^+ e^-$ with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining $X17$ parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the $X17$ decay with the proposed method. To reach this goal an optimization of the $X17$ production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results [Phys. Rev. D101, 071101 (2020)], validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate shows that the goal of the proposed search is feasible.
Published: 2020

32. Triangle Singularity as the Origin of the $a_1(1420)$

Author: Alexeev, G. D., Alexeev, M. G., Amoroso, A., Andrieux, V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Antequera, J. Berenguer, Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Efremov, A., Eversheim, P. D., Faccioli, P., Faessler, M., Finger, M., Finger jr., M., Fischer, H., Franco, C., Friedrich, J. M., Frolov, V., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Guskov, A., von Harrach, D., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Joerg, P., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Mattson, G., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Naim, C., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevskiy, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pesek, M., Peshekhonov, D. V., Peskova, M., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Reicherz, G., Riedl, C., Rudnicki, T., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sinha, L., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Sznajder, P., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Townsend, A., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veit, B. M., Veloso, J., Ventura, B., Vidon, A., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavada, P., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., Zhao, Y., and Ziembicki, M.
Subjects: High Energy Physics - Phenomenology, High Energy Physics - Experiment
Abstract: The COMPASS experiment recently discovered a new isovector resonance-like signal with axial-vector quantum numbers, the $a_1(1420)$, decaying to $f_0(980)\pi$. With a mass too close to and a width smaller than the axial-vector ground state $a_1(1260)$, it was immediately interpreted as a new light exotic meson, similar to the $X$, $Y$, $Z$ states in the hidden-charm sector. We show that a resonance-like signal fully matching the experimental data is produced by the decay of the $a_1(1260)$ resonance into $K^\ast(\to K\pi)\bar{K}$ and subsequent rescattering through a triangle singularity into the coupled $f_0(980)\pi$ channel. The amplitude for this process is calculated using a new approach based on dispersion relations. The triangle-singularity model is fitted to the partial-wave data of the COMPASS experiment. Despite having less parameters, this fit shows a slightly better quality than the one using a resonance hypothesis and thus eliminates the need for an additional resonance in order to describe the data. We thereby demonstrate for the first time in the light-meson sector that a resonance-like structure in the experimental data can be described by rescattering through a triangle singularity, providing evidence for a genuine three-body effect., Comment: 7 pages, 5 figures
Published: 2020
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33. Search for Axionlike and Scalar Particles with the NA64 Experiment

Author: Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as shielding, and would be observed either through their $a(s)\to\gamma \gamma$ decay in the rest of the HCAL detector or as events with large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to $2.84\times10^{11}$ electrons on target allowing to set new limits on the $a(s)\gamma\gamma$-coupling strength for a(s) masses below 55 MeV., Comment: This publication is dedicated to the memory of our colleague Danila Tlisov. 7 pages, 5 figures, revised version accepted for publication in Phys. Rev. Lett
Published: 2020
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34. Antiproton over proton and K$^-$ over K$^+$ multiplicity ratios at high $z$ in DIS

Author: Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Antequera, J. Berenguer, Bernhard, J., Bodlak, M., Bradamante, F., Bressan, A., Buechele, M., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisenko, I., Denisov, O. Yu., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Efremov, A., Eversheim, P. D., Faccioli, P., Faessler, M., Finger, M., Finger jr., M., Fischer, H., Franco, C., Friedrich, J. M., Frolov, V., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Guskov, A., von Harrach, D., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Joerg, P., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Mattson, G., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Naim, C., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevskiy, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pesek, M., Peshekhonov, D. V., Peskova, M., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Reicherz, G., Riedl, C., Rudnicki, T., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sinha, L., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Sznajder, P., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Townsend, A., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veit, B. M., Veloso, J., Ventura, B., Vidon, A., Virius, M., Wagner, M., Wallner, S., Zaremba, K., Zavada, P., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., Zhao, Y., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, Nuclear Experiment
Abstract: The $\bar{\rm p} $ over p multiplicity ratio is measured in deep-inelastic scattering for the first time using (anti-) protons carrying a large fraction of the virtual-photon energy, $z>0.5$. The data were obtained by the COMPASS Collaboration using a 160 GeV muon beam impinging on an isoscalar $^6$LiD target. The regime of deep-inelastic scattering is ensured by requiring $Q^2$ > 1 (GeV/$c$)$^2$ for the photon virtuality and $W > 5$ GeV/$c^2$ for the invariant mass of the produced hadronic system. The range in Bjorken-$x$ is restricted to $0.01 < x < 0.40$. Protons and antiprotons are identified in the momentum range $20 \div 60$ GeV/$c$. In the whole studied $z$-region, the $\bar{\rm p}$ over p multiplicity ratio is found to be below the lower limit expected from calculations based on leading-order perturbative Quantum Chromodynamics (pQCD). Extending our earlier analysis of the K$^-$ over K$^+$ multiplicity ratio by including now events with larger virtual-photon energies, this ratio becomes closer to the expectation of next-to-leading order pQCD. The results of both analyses strengthen our earlier conclusion that the phase space available for hadronisation should be taken into account in the pQCD formalism., Comment: 19 pages, 7 figures, 3 tables
Published: 2020
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35. Improved limits on a hypothetical X(16.7) boson and a dark photon decaying into $e^+e^-$ pairs

Author: Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Subjects: High Energy Physics - Experiment
Abstract: The improved results on a direct search for a new X(16.7 MeV) boson which could explain the anomalous excess of $e^+e^-$ pairs observed in the excited 8Be nucleus decays ("Berillium anomaly") are reported. Due to its coupling to electrons, the X boson could be produced in the bremsstrahlung reaction e-Z -> e-ZX by a high-energy beam of electrons incident on active target in the NA64 experiment at the CERN SPS and observed through its subsequent decay into $e^+e^-$ pair. No evidence for such decays was found from the combined analysis of the data samples with total statistics corresponding to 8.4\times 10^{10} electrons on target collected in 2017 and 2018. This allows to set the new limits on the $X$--$e^-$ coupling in the range 1.2 \times 10^{-4} < \epsilon_e < 6.8 \times 10^{-4}, excluding part of the parameter space favored by the Berillium anomaly. We also set new bounds on the mixing strength of photons with dark photons (A') from non-observation of the decay $A' \to e^+e^-$ of the bremsstrahlung A' with a mass below 24 MeV., Comment: 7 pages, 5 figures, 1 table. arXiv admin note: substantial text overlap with arXiv:1803.07748
Published: 2019
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36. Contribution of exclusive diffractive processes to the measured azimuthal asymmetries in SIDIS

Author: Agarwala, J., Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anfimov, N. V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Antequera, J. Berenguer, Bernhard, J., Bodlak, M., Bordalo, P., Bradamante, F., Bressan, A., Buechele, M., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P. M. M., Crespo, M. L., D'Ago, D., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisenko, I., Denisov, O. Yu., Dhara, L., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Efremov, A., Eversheim, P. D., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., Friedrich, J. M., Frolov, V., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Guskov, A., von Harrach, D., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Joerg, P., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Krinner, F., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lavickova, K., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Mattson, G., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Naim, C., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevskiy, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Pekeler, H., Peng, J. -C., Pereira, F., Pesek, M., Peshekhonov, D. V., Peskova, M., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rudnicki, T., Rybnikov, A., Rychter, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Sinha, L., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Sznajder, P., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Townsend, A., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veit, B. M., Veloso, J., Ventura, B., Vidon, A., Virius, M., Wagner, M., Wallner, S., Wilfert, M., Zaremba, K., Zavada, P., Zavertyaev, M., Zemko, M., Zemlyanichkina, E., Zhao, Y., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: Hadron leptoproduction in Semi-Inclusive measurements of Deep-Inelastic Scattering (SIDIS) on unpolarised nucleons allows one to get information on the intrinsic transverse momentum of quarks in a nucleon and on the Boer-Mulders function through the measurement of azimuthal modulations in the cross section. These modulations were recently measured by the HERMES experiment at DESY on proton and deuteron targets, and by the COMPASS experiment using the CERN SPS muon beam and a $^6$LiD target. In both cases, the amplitudes of the $\cos\phi_h$ and $\cos 2\phi_h$ modulations show strong kinematic dependences for both positive and negative hadrons. It has been known since some time that the measured final-state hadrons in those SIDIS experiments receive a contribution from exclusive diffractive production of vector mesons, particularly important at large values of $z$, the fraction of the virtual photon energy carried by the hadron. In previous measurements of azimuthal asymmetries this contribution was not taken into account, because it was not known that it could distort the azimuthal modulations. Presently, a method to evaluate the contribution of the exclusive reactions to the azimuthal asymmetries measured by COMPASS has been developed. The subtraction of this contribution results in a better understanding of the kinematic effects, and the remaining non-zero $\cos 2\phi_h$ modulation gives indication for a non-zero Boer-Mulders effect., Comment: 13 pages, 7 figures
Published: 2019
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37. Dark matter search in missing energy events with NA64

Author: Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: A search for sub-GeV dark matter production mediated by a new vector boson $A'$, called dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with $2.84\times10^{11}$ electrons on target no evidence of such a process has been found. The most stringent constraints on the $A'$ mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range $\lesssim 0.2$ GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search., Comment: 6 pages, 4 figures, version accepted for publication in Phys. Rev. Lett. arXiv admin note: text overlap with arXiv:1710.00971, arXiv:1610.02988
Published: 2019
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38. Measurement of the $K^+\rightarrow{\mu^+}{\nu_{\mu}}{\gamma}$ decay form factors in the OKA experiment

Author: Kravtsov, V. I., Duk, V. A., Filippov, S. N., Gushchin, E. N., Khudyakov, A. A., Kudenko, Yu. G., Polyarush, A. Yu., Akimenko, S. A., Artamonov, A. V., Blik, A. M., Burtovoy, V. S., Donskov, S. V., Filin, A. P., Gorin, A. M., Inyakin, A. V., Khaustov, G. V., Kholodenko, S. A., Kolosov, V. N., Kurshetsov, V. F., Lishin, V. A., Medynsky, M. V., Mikhailov, Yu. V., Obraztsov, V. F., Polyakov, V. A., Popov, A. V., Romanovsky, V. I., Rykalin, V. I., Sadovsky, A. S., Samoilenko, V. D., Semenov, V. K., Shapkin, M. M., Stenyakin, O. V., Tchikilev, O. G., Uvarov, V. A., Yushchenko, O. P., Bychkov, V. N., Kekelidze, G. D., Lysan, V. M., and Zalikhanov, B. Zh.
Subjects: High Energy Physics - Experiment, Nuclear Experiment
Abstract: A precise measurement of the vector and axial-vector form factors difference $F_V-F_A$ in the $K^+\rightarrow{\mu^+}{\nu_{\mu}}{\gamma}$ decay is presented. About 95K events of $K^+\rightarrow{\mu^+}{\nu_{\mu}}{\gamma}$ are selected in the OKA experiment. The result is $F_V-F_A=0.134\pm0.021(stat)\pm0.027(syst)$. Both errors are smaller than in the previous $F_V-F_A$ measurements., Comment: 9 pages, 8 figures
Published: 2019
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39. Measurement of the cross section for hard exclusive $\pi^0$ leptoproduction

Author: Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anfimov, N. V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bodlak, M., Bordalo, P., Bradamante, F., Bressan, A., Buechele, M., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Crespo, M. L., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisov, O. Yu., Dhara, L., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Efremov, A., Eversheim, P. D., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., von Hohenesche, N. du Fresne, Friedrich, J. M., Frolov, V., Fuchey, E., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Guskov, A., Hahne, D., Hamar, G., von Harrach, D., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Joerg, P., Juraskova, K., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Kral, Z., Kraemer, M., Krinner, F., Kroumchtein, Z. V., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Lin, P. -J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Naim, C., Nagaytsev, A., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevskiy, A. G., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Peng, J. -C., Pereira, F., Pesek, M., Peshekhonov, D. V., Peskova, M., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Regali, C., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sbrizzai, G., Schmieden, H., Selyunin, A., Silva, L., Sinha, L., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Szameitat, T., Sznajder, P., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veit, B. M., Veloso, J., Vidon, A., Virius, M., Wagner, M., Wallner, S., Wilfert, M., Zaremba, K., Zavada, P., Zavertyaev, M., Zemlyanichkina, E., Zhao, Y., and Ziembicki, M.
Subjects: High Energy Physics - Experiment
Abstract: We report on a measurement of hard exclusive $\pi^0$ muoproduction on the proton by COMPASS using 160 GeV/$c$ polarised $\mu^+$ and $\mu^-$ beams of the CERN SPS impinging on a liquid hydrogen target. From the average of the measured $\mu^+$ and $\mu^-$ cross sections, the virtual-photon proton cross section is determined as a function of the squared four-momentum transfer between initial and final proton in the range $0.08\,(\text{GeV/}c)^2 < |t| < 0.64\,(\text{GeV/}c)^2$. The average kinematics of the measurement are $\langle Q^2 \rangle =2.0\; {(\text{GeV}/c)^2}$, $\langle \nu \rangle = 12.8\; {\text{GeV}}$, $\langle x_{Bj} \rangle = 0.093 $ and $\langle -t \rangle = 0.256\; {(\text{GeV}/c)^2} $. Fitting the azimuthal dependence reveals a combined contribution by transversely and longitudinally polarised photons of $(8.1 \ \pm \ 0.9_{\text{stat}}{}_{- \ 1.0}^{+ \ 1.1}\big\rvert_{\text{sys}})\,{\text{nb}}/{(\text{GeV}/c)^{2}}$, as well as transverse-transverse and longitudinal-transverse interference contributions of $(-6.0 \pm 1.3_{\text{stat}}{}_{- \ 0.7}^{+ \ 0.7}\big\rvert_{\text{sys}})\,{\text{nb}}/{(\text{GeV}/c)^{2}}$ and $(1.4 \pm 0.5_{\text{stat}}{}_{- \ 0.2}^{+ \ 0.3}\big\rvert_{\text{sys}})\,{\text{nb}}/{(\text{GeV}/c)^{2}}$, respectively. Our results provide important input for modelling Generalised Parton Distributions. In the context of the phenomenological Goloskokov-Kroll model, the statistically significant transverse-transverse interference contribution constitutes clear experimental evidence for the chiral-odd GPD $\overline{E}_T$., Comment: 9 pages, 5 figures
Published: 2019
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40. Measurement of $P_T$-weighted Sivers asymmetries in leptoproduction of hadrons

Author: Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anfimov, N. V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barone, V., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bicker, K., Bielert, E. R., Bodlak, M., Bordalo, P., Bradamante, F., Bressan, A., Buechele, M., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Crespo, M. L., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisov, O. Yu., Dhara, L., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Dziewiecki, M., Efremov, A., Elia, C., Eversheim, P. D., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., von Hohenesche, N. du Fresne, Friedrich, J. M., Frolov, V., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Guskov, A., Hahne, D., Hamar, G., von Harrach, D., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Joerg, P., Juraskova, K., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Kral, Z., Kraemer, M., Krinner, F., Kroumchtein, Z. V., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lednev, A. A., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevskiy, A. G., Orlov, I., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Peng, J. -C., Pereira, F., Pesek, M., Peskova, M., Peshekhonov, D. V., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Regali, C., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Salac, R., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sawada, T., Sbrizzai, G., Schiavon, P., Schmieden, H., Seder, E., Selyunin, A., Silva, L., Sinha, L., Sirtl, S., Slunecka, M., Smolik, J., Sozzi, F., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Szameitat, T., Sznajder, P., Tasevsky, M., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veit, B. M., Veloso, J., Vidon, A., Virius, M., Wagner, M., Wallner, S., Wilfert, M., Zaremba, K., Zavada, P., Zavertyaev, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: The transverse spin asymmetries measured in semi-inclusive leptoproduction of hadrons, when weighted with the hadron transverse momentum $P_T$, allow for the extraction of important transverse-momentum-dependent distribution functions. In particular, the weighted Sivers asymmetries provide direct information on the Sivers function, which is a leading-twist distribution that arises from a correlation between the transverse momentum of an unpolarised quark in a transversely polarised nucleon and the spin of the nucleon. Using the high-statistics data collected by the COMPASS Collaboration in 2010 with a transversely polarised proton target, we have evaluated two types of $P_T$-weighted Sivers asymmetries, which are both proportional to the product of the firsttransverse moment of the Sivers function and of the fragmentation function. The results are compared to the standard unweighted Sivers asymmetries and used to extract the first transverse moments of the Sivers distributions for $u$ and $d$ quarks., Comment: 23 pages, 12 figures
Published: 2018
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41. Study of the decay $K^{+}\to\pi^{+}\pi^{-}\pi^{+}\gamma$ in the OKA experiment

Author: Shapkin, M. M., Akimenko, S. A., Artamonov, A. V., Blik, A. M., Burtovoy, V. S., Donskov, S. V., Filin, A. P., Inyakin, A. V., Gorin, A. M., Khaustov, G. V., Kholodenko, S. A., Kolosov, V. N., Konstantinov, A. S., Kurshetsov, V. F., Lishin, V. A., Medynsky, M. V., Mikhailov, Yu. V., Obraztsov, V. F., Polyakov, V. A., Popov, A. V., Romanovsky, V. I., Rykalin, V. I., Sadovsky, A. S., Samoilenko, V. D., Semenov, V. K., Stenyakin, O. V., Tchikilev, O. G., Uvarov, V. A., Yushchenko, O. P., Duk, V. A., Filippov, S. N., Guschin, E. N., Khudyakov, A. A., Kravtsov, V. I., Kudenko, Yu. G., Polyarush, A. Yu., Bychkov, V. N., Kekelidze, G. D., Lysan, V. M., and Zalikhanov, B. Zh.
Subjects: High Energy Physics - Experiment
Abstract: A high statistics data sample of the decays of $K^+$ mesons to three charged particles was accumulated by the OKA experiment in 2012 and 2013. This allowed to select a clean sample of about 450 events with $K^{+}\to\pi^{+}\pi^{-}\pi^{+}\gamma$ decays with the energy of the photon in the kaon rest frame greater than 30 MeV. The measured branching fraction of the $K^{+}\to\pi^{+}\pi^{-}\pi^{+}\gamma$, with $E_{\gamma}^{*}$ > 30 MeV is $(0.71 \pm 0.05) \times 10^{-5}$. The measured energy spectrum of the decay photon is compared with the prediction of the chiral perturbation theory to O$(p^{4})$. A search for an up-down asymmetry of the photon with respect to the hadronic system decay plane is also performed., Comment: 9 pages, 7 figures, 1 table
Published: 2018
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42. Letter of Intent: A New QCD facility at the M2 beam line of the CERN SPS (COMPASS++/AMBER)

Author: Adams, B., Aidala, C. A., Akhunzyanov, R., Alexeev, G. D., Alexeev, M. G., Amoroso, A., Andrieux, V., Anfimov, N. V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Azhibekov, A., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Antequera, J. Berenguer, Bernauer, J. C., Bernhard, J., Bodlak, M., Bordalo, P., Bradamante, F., Bressan, A., Buchele, M., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chen, X., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Correia, P., Crespo, M. L., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Dashyan, N., Denisenko, I., Denisov, O. Yu., Dhara, L., d'Hose, N., Donato, F., Donskov, S. V., Doshita, N., Dreisbach, Ch., Dunnweber, W., Dusaev, R. R., Dziewiecki, M., Dzyuba, A., Efremov, A., Egelhof, P., Elagin, A., Eversheim, P. D., Faessler, M., Fedotova, J., Ferrero, A., Finger, M., Finger Jr., M., Fischer, H., Franco, C., Friedrich, J. M., Frolov, V., Futch, A., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Gevorkyan, S., Ghandilyan, Y., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Gushterski, R. I., Guskov, A., Hahne, D., Hamar, G., von Harrach, D., He, X., Heitz, R., Herrmann, F., Horikawa, N., Hsieh, C. -Y., Huber, S., Inglessi, A., Ilyichev, A., Isataev, T., Ishimoto, S., Ivanov, A., Ivanov, N., Ivanshin, Yu., Iwata, T., Jandek, M., Jary, V., Jen, C. -M., Joosten, R., Joerg, P., Juraskova, K., Kabuss, E., Kabyshev, A., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kim, M., Kiselev, O., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Koval, A., Kral, Z., Kraemer, M., Krinner, F., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kuterbekov, K., Kuznetsov, I. I., Kveton, A., Levchenko, E. A., Levorato, S., Lian, Y. -S., Liang, Y., Lichtenstadt, J., Lin, P. -J., Liu, K., Liu, M. X., Longo, R., Lorenzon, W., Losekamm, M., Lyubovitskij, V. E., Maev, E., Maggiora, A., Magnon, A., Makarenko, V., Makins, N., Makke, N., Mallot, G. K., Maltsev, A., Mamon, S. A., Marianski, B., Martin, A., Marukyan, H., Marzec, J., Masi, N., Matousek, J., Matsuda, H., Mattson, G., Meshcheryakov, G. V., Meyer, W., Meyer, M., Mikhailov, Yu. V., Mikhasenko, M., Minot, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Naim, C., Neyret, D., Nigmatkulov, G., Mkrtchyan, A., Mkrtchyan, H., Novy, J., Nowak, W. -D., Nozzoli, F., Nukazuka, G., Nunes, A. S., Olshevsky, A. G., Orlov, I., Osborn, J. D., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Peng, J. -C., Pereira, F., Peshekhonov, D. V., Pesek, M., Peskova, M., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Poeschl, T., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Raymond, R., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Salac, R., Samoylenko, V. D., Sandacz, A., Sarkar, S., Sarsour, M., Savin, I. A., Sbrizzai, G., Schmieden, H., Seder, E., Selyunin, A., Simon, H., Sinha, L., Sirtl, S., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Sznajder, P., Tasevsky, M., Tchekhovski, V., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Tskhay, V., Uhl, S., Vasilishin, B. I., Vassiliev, A., Vauth, A., Veit, B. M., Ventura, B., Veloso, J., Vidon, A., Virius, M., Vorobyev, A., Wagner, M., Wallner, S., Wilfert, M., Xiao, Z., Xu, N., Yang, J., Zaremba, K., Zavada, P., Zavertyaev, M., Zemlyanichkina, E., Zhao, H., Zhao, Y., Zhuravlev, N., Ziembicki, M., and Zuccon, P.
Subjects: High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract: A New QCD facility at the M2 beam line of the CERN SPS COMPASS++/AMBER, Comment: 91 pages, 51 figures
Published: 2018

43. Search for a Hypothetical 16.7 MeV Gauge Boson and Dark Photons in the NA64 Experiment at CERN

Author: Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V., and Ulloa, P.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e+e- pairs observed in the excited Be-8 nucleus decays. Due to its coupling to electrons, the X could be produced in the bremsstrahlung reaction e- Z -> e- Z X by a 100 GeV e- beam incident on an active target in the NA64 experiment at the CERN SPS and observed through the subsequent decay into an e+e- pair. With 5.4\times 10^{10} electrons on target, no evidence for such decays was found, allowing to set first limits on the X-e^- coupling in the range 1.3\times 10^{-4} < \epsilon_e < 4.2\times 10^{-4} excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A') from non-observation of the decay A'->e+e- of the bremsstrahlung A' with a mass <~ 23 MeV., Comment: 6 pages, 3 figures. Title changed as suggested by Journal; references added; version published in Phys. Rev. Lett
Published: 2018
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44. Light isovector resonances in $\pi^- p \to \pi^-\pi^-\pi^+ p$ at 190 GeV/${\it c}$

Author: Aghasyan, M., Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anfimov, N. V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Austregesilo, A., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bicker, K., Bielert, E. R., Birsa, R., Bodlak, M., Bordalo, P., Bradamante, F., Bressan, A., Buechele, M., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Choi, I., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Crespo, M. L., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisov, O. Yu., Dhara, L., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Dziewiecki, M., Efremov, A., Eversheim, P. D., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., von Hohenesche, N. du Fresne, Friedrich, J. M., Frolov, V., Fuchey, E., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Grussenmeyer, T., Guskov, A., Hass, F., Hahne, D., Hamar, G., von Harrach, D., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Ivanshin, Yu., Iwata, T., Jary, V., Joosten, R., Joerg, P., Juraskova, K., Kabuss, E., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Kral, Z., Kraemer, M., Krinner, F., Kroumchtein, Z. V., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kuznetsov, I. I., Kveton, A., Lednev, A. A., Levchenko, E. A., Levillain, M., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, H., Matsuda, T., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Nerling, F., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevsky, A. G., Orlov, I., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Peng, J. -C., Pereira, F., Pesek, M., Peskova, M., Peshekhonov, D. V., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Regali, C., Reicherz, G., Riedl, C., Rogacheva, N. S., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Salac, R., Samoylenko, V. D., Sandacz, A., Santos, C., Sarkar, S., Savin, I. A., Sawada, T., Sbrizzai, G., Schiavon, P., Schluter, T., Schmeing, S., Schmieden, H., Seder, E., Selyunin, A., Silva, L., Sinha, L., Sirtl, S., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Szameitat, T., Sznajder, P., Tasevsky, M., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veit, B. M., Veloso, J., Vidon, A., Virius, M., Wallner, S., Wilfert, M., ter Wolbeek, J., Zaremba, K., Zavada, P., Zavertyaev, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We have performed the most comprehensive resonance-model fit of $\pi^-\pi^-\pi^+$ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation events from the reaction $\pi^- + p \to \pi^-\pi^-\pi^+ + p_\text{recoil}$ with a 190 GeV/$c$ pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, $0.5 < m_{3\pi} < 2.5$ GeV/$c^2$, and simultaneously in 11 bins of the reduced four-momentum transfer squared, $0.1 < t' < 1.0$ $($GeV$/c)^2$, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with $J^{PC} = 0^{-+}$, $1^{++}$, $2^{++}$, $2^{-+}$, $4^{++}$, and spin-exotic $1^{-+}$ quantum numbers. The model contains the well-known resonances $\pi(1800)$, $a_1(1260)$, $a_2(1320)$, $\pi_2(1670)$, $\pi_2(1880)$, and $a_4(2040)$. In addition, it includes the disputed $\pi_1(1600)$, the excited states $a_1(1640)$, $a_2(1700)$, and $\pi_2(2005)$, as well as the resonancelike $a_1(1420)$. We measure the resonance parameters mass and width of these objects by combining the information from the PWA results obtained in the 11 $t'$ bins. We extract the relative branching fractions of the $\rho(770) \pi$ and $f_2(1270) \pi$ decays of $a_2(1320)$ and $a_4(2040)$, where the former one is measured for the first time. In a novel approach, we extract the $t'$ dependence of the intensity of the resonances and of their phases. The $t'$ dependence of the intensities of most resonances differs distinctly from the $t'$ dependence of the nonresonant components. For the first time, we determine the $t'$ dependence of the phases of the production amplitudes and confirm that the production mechanism of the Pomeron exchange is common to all resonances., Comment: 224 pages, 172 figures
Published: 2018
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45. Transverse Extension of Partons in the Proton probed by Deeply Virtual Compton Scattering

Author: Akhunzyanov, R., Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anfimov, N. V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Austregesilo, A., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bicker, K., Bielert, E. R., Birsa, R., Bodlak, M., Bordalo, P., Bradamante, F., Bressan, A., Buechele, M., Burtin, E., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Choi, I., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Crespo, M. L., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisov, O. Yu., Dhara, L., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Dziewiecki, M., Efremov, A., Eversheim, P. D., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., von Hohenesche, N. du Fresne, Friedrich, J. M., Frolov, V., Fuchey, E., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Grussenmeyer, T., Guskov, A., Hahne, D., Hamar, G., von Harrach, D., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Ivanshin, Yu., Iwata, T., Jary, V., Joosten, R., Joerg, P., Juraskova, K., Kabuss, E., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Kral, Z., Kraemer, M., Krinner, F., Kroumchtein, Z. V., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kuznetsov, I. I., Kveton, A., Lednev, A. A., Levchenko, E. A., Levillain, M., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Mamon, S. A., Marchand, C., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, H., Matsuda, T., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Nerling, F., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevsky, A. G., Orlov, I., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Peng, J. -C., Pereira, F., Pesaro, G., Pesek, M., Peskova, M., Peshekhonov, D. V., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Regali, C., Reicherz, G., Riedl, C., Rogacheva, N. S., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Salac, R., Samoylenko, V. D., Sandacz, A., Santos, C., Sarkar, S., Savin, I. A., Sawada, T., Sbrizzai, G., Schiavon, P., Schmieden, H., Schoennig, K., Seder, E., Selyunin, A., Silva, L., Sinha, L., Sirtl, S., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Szameitat, T., Sznajder, P., Tasevsky, M., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veit, B. M., Veloso, J., Vidon, A., Virius, M., Wallner, S., Wilfert, M., ter Wolbeek, J., Zaremba, K., Zavada, P., Zavertyaev, M., Zemlyanichkina, E., Zhuravlev, N., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, Nuclear Experiment
Abstract: We report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/$c$ polarized $\mu^+$ and $\mu^-$ beams of the CERN SPS impinging on a liquid hydrogen target. We determine the dependence of the average of the measured $\mu^+$ and $\mu^-$ cross sections for deeply virtual Compton scattering on the squared four-momentum transfer $t$ from the initial to the final final proton. The slope $B$ of the $t$-dependence is fitted with a single exponential function, which yields $B=(4.3 \ \pm \ 0.6_{\text{stat}}\_{- \ 0.3}^{+ \ 0.1}\big\rvert_{\text{sys}}) (\text{GeV}/c)^{-2}$. This result can be converted into an average transverse extension of partons in the proton, $\sqrt{\langle r_{\perp}^2 \rangle} = (0.58 \ \pm \ 0.04_{\text{stat}}\_{- \ 0.02}^{+ \ 0.01}\big\rvert_{\text{sys}})\text{fm}$. For this measurement, the average virtuality of the photon mediating the interaction is $\langle Q^2 \rangle = 1.8\,(\text{GeV/}c)^2$ and the average value of the Bjorken variable is $\langle x_{\text{Bj}} \rangle = 0.056$., Comment: 13 pages, 5 figures
Published: 2018
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46. K$^{-}$ over K$^{+}$ multiplicity ratio for kaons produced in DIS with a large fraction of the virtual-photon energy

Author: Akhunzyanov, R., Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anfimov, N. V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bicker, K., Bielert, E. R., Bodlak, M., Bordalo, P., Bradamante, F., Bressan, A., Buechele, M., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Crespo, M. L., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisov, O. Yu., Dhara, L., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Dziewiecki, M., Efremov, A., Elia, C., Eversheim, P. D., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., von Hohenesche, N. du Fresne, Friedrich, J. M., Frolov, V., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Guskov, A., Hahne, D., Hamar, G., von Harrach, D., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Iwata, T., Jandek, M., Jary, T., Joosten, R., Joerg, P., Juraskova, K., Kabuss, E., Kaspar, F., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Kral, Z., Kraemer, M., Krinner, F., Kroumchtein, Z. V., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kveton, A., Lednev, A. A., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, T., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevskiy, A. G., Orlov, I., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Peng, J. -C., Pereira, F., Pesek, M., Peskova, M., Peshekhonov, D. V., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Regali, C., Reicherz, G., Riedl, C., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Salac, R., Samoylenko, V. D., Sandacz, A., Sarkar, S., Savin, I. A., Sawada, T., Sbrizzai, G., Schmieden, H., Seder, E., Selyunin, A., Silva, L., Sinha, L., Sirtl, S., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Szameitat, T., Sznajder, P., Tasevsky, M., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veit, B. M., Veloso, J., Vidon, A., Virius, M., Wagner, M., Wallner, S., Wilfert, M., Zaremba, K., Zavada, P., Zavertyaev, M., Zemlyanichkina, E., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: The K$^{-}$ over K$^{+}$ multiplicity ratio is measured in deep-inelastic scattering, for the first time for kaons carrying a large fraction $z$ of the virtual-photon energy. The data were obtained by the COMPASS collaboration using a 160 GeV muon beam and an isoscalar $^6$LiD target. The regime of deep-inelastic scattering is ensured by requiring $Q^2>1$ (GeV/$c)^2$ for the photon virtuality and $W>5$ GeV/$c^2$ for the invariant mass of the produced hadronic system. Kaons are identified in the momentum range from 12 GeV/$c$ to 40 GeV/$c$, thereby restricting the range in Bjorken-$x$ to $0.010.75$. For very large values of $z$, $i.e.$ $z>0.8$, we observe the kaon multiplicity ratio to fall below the lower limits expected from calculations based on leading and next-to-leading order perturbative quantum chromodynamics. Also, the kaon multiplicity ratio shows a strong dependence on the missing mass of the single-kaon production process. This suggests that within the perturbative quantum chromodynamics formalism an additional correction may be required, which takes into account the phase space available for hadronisation., Comment: 16 pages, 7 figures
Published: 2018
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47. Longitudinal double-spin asymmetry $A_1^{\rm p}$ and spin-dependent structure function $g_1^{\rm p}$ of the proton at small values of $x$ and $Q^2$

Author: Aghasyan, M., Akhunzyanov, R., Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anfimov, N. V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Austregesilo, A., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bicker, K., Bielert, E. R., Birsa, R., Bodlak, M., Bordalo, P., Bradamante, F., Bressan, A., Buechele, M., Burtsev, V. E., Chang, W. -C., Chatterjee, C., Chiosso, M., Choi, I., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Crespo, M. L., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisov, O. Yu., Dhara, L., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Dziewiecki, M., Efremov, A., Eversheim, P. D., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., von Hohenesche, N. du Fresne, Friedrich, J. M., Frolov, V., Fuchey, E., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, F., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Grussenmeyer, T., Guskov, A., Hahne, D., Hamar, G., von Harrach, D., Heinsius, F. H., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Ivanshin, Yu., Iwata, T., Jary, V., Joosten, R., Joerg, P., Kabuss, E., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Koenigsmann, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Kral, Z., Kraemer, M., Kremser, P., Krinner, F., Kroumchtein, Z. V., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kuznetsov, I. I., Kveton, A., Lednev, A. A., Levchenko, E. A., Levillain, M., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, H., Matsuda, T., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Nerling, F., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevsky, A. G., Orlov, I., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Peng, J. -C., Pereira, F., Pesek, M., Peskova, M., Peshekhonov, D. V., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Regali, C., Reicherz, G., Riedl, C., Rogacheva, N. S., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Salac, R., Samoylenko, V. D., Sandacz, A., Santos, C., Sarkar, S., Savin, I. A., Sawada, T., Sbrizzai, G., Schiavon, P., Schmidt, K., Schmieden, H., Schoenning, K., Seder, E., Selyunin, A., Silva, L., Sinha, L., Sirtl, S., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Szameitat, T., Sznajder, P., Tasevsky, M., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veloso, J., Vidon, A., Virius, M., Wallner, S., Weisrock, T., Wilfert, M., ter Wolbeek, J., Zaremba, K., Zavada, P., Zavertyaev, M., Zemlyanichkina, E., Zhuravlev, N., and Ziembicki, M.
Subjects: High Energy Physics - Experiment
Abstract: We present a precise measurement of the proton longitudinal double-spin asymmetry $A_1^{\rm p}$ and the proton spin-dependent structure function $g_1^{\rm p}$ at photon virtualities $0.006~({\rm GeV}/c)^2
Published: 2017
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48. Search for vector mediator of Dark Matter production in invisible decay mode

Author: NA64 Collaboration, Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, and Ulloa, P.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: A search is performed for a new sub-GeV vector boson ($A'$) mediated production of Dark Matter ($\chi$) in the fixed-target experiment, NA64, at the CERN SPS. The $A'$, called dark photon, could be generated in the reaction $ e^- Z \to e^- Z A'$ of 100 GeV electrons dumped against an active target which is followed by the prompt invisible decay $A' \to \chi \overline{\chi}$. The experimental signature of this process would be an event with an isolated electron and large missing energy in the detector. From the analysis of the data sample collected in 2016 corresponding to $4.3\times10^{10}$ electrons on target no evidence of such a process has been found. New stringent constraints on the $A'$ mixing strength with photons, $10^{-5}\lesssim \epsilon \lesssim 10^{-2}$, for the $A'$ mass range $m_{A'} \lesssim 1$ GeV are derived. For models considering scalar and fermionic thermal Dark Matter interacting with the visible sector through the vector portal the 90% C.L. limits $10^{-11}\lesssim y \lesssim 10^{-6}$ on the dark-matter parameter $y = \epsilon^2 \alpha_D (\frac{m_\chi}{m_{A'}})^4 $ are obtained for the dark coupling constant $\alpha_D = 0.5$ and dark-matter masses $0.001 \lesssim m_\chi \lesssim 0.5 $ GeV. The lower limits $\alpha_D \gtrsim 10^{-3} $ for pseudo-Dirac Dark Matter in the mass region $m_\chi \lesssim 0.05 $ GeV are more stringent than the corresponding bounds from beam dump experiments. The results are obtained by using tree level, exact calculations of the $A'$ production cross-sections, which turn out to be significantly smaller compared to the one obtained in the Weizs\"{a}cker-Williams approximation for the mass region $m_{A'} \gtrsim 0.1$ GeV., Comment: 22 pages, 17 figures, version accepted for publication in PRD
Published: 2017
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49. Transverse-momentum-dependent Multiplicities of Charged Hadrons in Muon-Deuteron Deep Inelastic Scattering

Author: Aghasyan, M., Akhunzyanov, R., Alexeev, M. G., Alexeev, G. D., Amoroso, A., Andrieux, V., Anfimov, N. V., Anosov, V., Antoshkin, A., Augsten, K., Augustyniak, W., Austregesilo, A., Azevedo, C. D. R., Badelek, B., Balestra, F., Ball, M., Barth, J., Beck, R., Bedfer, Y., Bernhard, J., Bicker, K., Bielert, E. R., Birsa, R., Bodlak, M., Bordalo, P., Bradamante, F., Bressan, A., Buechele, M., Burtsev, V. E., Capozza, L., Chang, W. -C., Chatterjee, C., Chiosso, M., Choi, I., Chumakov, A. G., Chung, S. -U., Cicuttin, A., Crespo, M. L., Curiel, Q., Torre, S. Dalla, Dasgupta, S. S., Dasgupta, S., Denisov, O. Yu., Dhara, L., Donskov, S. V., Doshita, N., Dreisbach, Ch., Duennweber, W., Dusaev, R. R., Dziewiecki, M., Efremov, A., Eversheim, P. D., Faessler, M., Ferrero, A., Finger, M., Finger jr., M., Fischer, H., Franco, C., von Hohenesche, N. du Fresne, Friedrich, J. M., Frolov, V., Fuchey, E., Gautheron, F., Gavrichtchouk, O. P., Gerassimov, S., Giarra, J., Giordano, F., Gnesi, I., Gorzellik, M., Grasso, A., Gridin, A., Perdekamp, M. Grosse, Grube, B., Grussenmeyer, T., Guskov, A., Hahne, D., Hamar, G., von Harrach, D., Heinsius, F. H., Heitz, R., Herrmann, F., Horikawa, N., d'Hose, N., Hsieh, C. -Y., Huber, S., Ishimoto, S., Ivanov, A., Ivanshin, Yu., Iwata, T., Jary, V., Joosten, R., Joerg, P., Kabuss, E., Kerbizi, A., Ketzer, B., Khaustov, G. V., Khokhlov, Yu. A., Kisselev, Yu., Klein, F., Koivuniemi, J. H., Kolosov, V. N., Kondo, K., Koenigsmann, K., Konorov, I., Konstantinov, V. F., Kotzinian, A. M., Kouznetsov, O. M., Kral, Z., Kraemer, M., Kremser, P., Krinner, F., Kroumchtein, Z. V., Kulinich, Y., Kunne, F., Kurek, K., Kurjata, R. P., Kuznetsov, I. I., Kveton, A., Lednev, A. A., Levchenko, E. A., Levillain, M., Levorato, S., Lian, Y. -S., Lichtenstadt, J., Longo, R., Lyubovitskij, V. E., Maggiora, A., Magnon, A., Makins, N., Makke, N., Mallot, G. K., Mamon, S. A., Marianski, B., Martin, A., Marzec, J., Matousek, J., Matsuda, H., Matsuda, T., Meshcheryakov, G. V., Meyer, M., Meyer, W., Mikhailov, Yu. V., Mikhasenko, M., Mitrofanov, E., Mitrofanov, N., Miyachi, Y., Moretti, A., Nagaytsev, A., Nerling, F., Neyret, D., Novy, J., Nowak, W. -D., Nukazuka, G., Nunes, A. S., Olshevsky, A. G., Orlov, I., Ostrick, M., Panzieri, D., Parsamyan, B., Paul, S., Peng, J. -C., Pereira, F., Pesek, M., Peskova, M., Peshekhonov, D. V., Pierre, N., Platchkov, S., Pochodzalla, J., Polyakov, V. A., Pretz, J., Quaresma, M., Quintans, C., Ramos, S., Regali, C., Reicherz, G., Riedl, C., Rogacheva, N. S., Ryabchikov, D. I., Rybnikov, A., Rychter, A., Salac, R., Samoylenko, V. D., Sandacz, A., Santos, C., Sarkar, S., Savin, I. A., Sawada, T., Sbrizzai, G., Schiavon, P., Schmidt, K., Schmieden, H., Schoenning, K., Seder, E., Selyunin, A., Silva, L., Sinha, L., Sirtl, S., Slunecka, M., Smolik, J., Srnka, A., Steffen, D., Stolarski, M., Subrt, O., Sulc, M., Suzuki, H., Szabelski, A., Szameitat, T., Sznajder, P., Tasevsky, M., Tessaro, S., Tessarotto, F., Thiel, A., Tomsa, J., Tosello, F., Tskhay, V., Uhl, S., Vasilishin, B. I., Vauth, A., Veloso, J., Vidon, A., Virius, M., Wallner, S., Weisrock, T., Wilfert, M., ter Wolbeek, J., Zaremba, K., Zavada, P., Zavertyaev, M., Zemlyanichkina, E., Zhuravlev, N., and Ziembicki, M.
Subjects: High Energy Physics - Experiment, Nuclear Experiment
Abstract: A semi-inclusive measurement of charged hadron multiplicities in deep inelastic muon scattering off an isoscalar target was performed using data collected by the COMPASS Collaboration at CERN. The following kinematic domain is covered by the data: photon virtuality $Q^{2}>1$ (GeV/$c$)$^2$, invariant mass of the hadronic system $W > 5$ GeV/$c^2$, Bjorken scaling variable in the range $0.003 < x < 0.4$, fraction of the virtual photon energy carried by the hadron in the range $0.2 < z < 0.8$, square of the hadron transverse momentum with respect to the virtual photon direction in the range 0.02 (GeV/$c)^2 < P_{\rm{hT}}^{2} < 3$ (GeV/$c$)$^2$. The multiplicities are presented as a function of $P_{\rm{hT}}^{2}$ in three-dimensional bins of $x$, $Q^2$, $z$ and compared to previous semi-inclusive measurements. We explore the small-$P_{\rm{hT}}^{2}$ region, i.e. $P_{\rm{hT}}^{2} < 1$ (GeV/$c$)$^2$, where hadron transverse momenta are expected to arise from non-perturbative effects, and also the domain of larger $P_{\rm{hT}}^{2}$, where contributions from higher-order perturbative QCD are expected to dominate. The multiplicities are fitted using a single-exponential function at small $P_{\rm{hT}}^{2}$ to study the dependence of the average transverse momentum $\langle P_{\rm{hT}}^{2}\rangle$ on $x$, $Q^2$ and $z$. The power-law behaviour of the multiplicities at large $P_{\rm{hT}}^{2}$ is investigated using various functional forms. The fits describe the data reasonably well over the full measured range., Comment: 28 pages, 20 figures
Published: 2017
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50. Search for heavy neutrino in $K^{+} \to \mu^{+} \nu_{H}$ decay

Author: Sadovsky, A. S., Kurshetsov, V. F., Filin, A. P., Akimenko, S. A., Artamonov, A. V., Blik, A. M., Brekhovskikh, V. V., Burtovoy, V. S., Donskov, S. V., Inyakin, A. V., Gorin, A. M., Khaustov, G. V., Kholodenko, S. A., Kolosov, V. N., Konstantinov, A. S., Leontiev, V. M., Lishin, V. A., Medynsky, M. V., Mikhailov, Yu. V., Obraztsov, V. F., Polyakov, V. A., Popov, A. V., Romanovsky, V. I., Rykalin, V. I., Samoilenko, V. D., Semenov, V. K., Stenyakin, O. V., Tchikilev, O. G., Uvarov, V. A., Yushchenko, O. P., Duk, V. A., Filippov, S. N., Gushchin, E. N., Khudyakov, A. A., Kravtsov, V. I., Kudenko, Yu. G., Polyarush, A. Yu., Bychkov, V. N., Kekelidze, G. D., Lysan, V. M., and Zalikhanov, B. Zh.
Subjects: High Energy Physics - Experiment
Abstract: A high statistics data sample of the $K^{+}\to\mu^{+}\nu_{\mu}$ decay was accumulated by the OKA experiment in 2012. The missing mass analysis was performed to search for the decay channel $K^{+}\to\mu^{+}\nu_{H}$ with a hypothetic stable heavy neutrino in the final state. The obtained missing mass spectrum does not show peaks which could be attributed to existence of stable heavy neutrinos in the mass range (220 $< m_{\nu_{H}} <$ 375) MeV$/c^{2}$. As a result, we obtain upper limits on the branching ratio and on the value of the mixing element $|U_{\mu H}|^{2}$., Comment: 11 pages, 10 figures
Published: 2017
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