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176 results on '"I, Keshelashvili"'

1. Spin decoherence and off-resonance behavior of radio-frequency-driven spin rotations in storage rings

Author

N. N. Nikolaev, F. Rathmann, J. Slim, A. Andres, V. Hejny, A. Nass, A. Kacharava, P. Lenisa, J. Pretz, A. Saleev, V. Shmakova, H. Soltner, F. Abusaif, A. Aggarwal, A. Aksentev, B. Alberdi, L. Barion, I. Bekman, M. Beyß, C. Böhme, B. Breitkreutz, N. Canale, G. Ciullo, S. Dymov, N.-O. Fröhlich, R. Gebel, M. Gaisser, K. Grigoryev, D. Grzonka, J. Hetzel, O. Javakhishvili, V. Kamerdzhiev, S. Karanth, I. Keshelashvili, A. Kononov, K. Laihem, A. Lehrach, N. Lomidze, B. Lorentz, G. Macharashvili, A. Magiera, D. Mchedlishvili, A. Melnikov, F. Müller, A. Pesce, V. Poncza, D. Prasuhn, D. Shergelashvili, N. Shurkhno, S. Siddique, A. Silenko, S. Stassen, E. J. Stephenson, H. Ströher, M. Tabidze, G. Tagliente, Y. Valdau, M. Vitz, T. Wagner, A. Wirzba, A. Wrońska, P. Wüstner, and M. Żurek

Subjects
Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

High-frequency driven resonant spin rotators are routinely used as standard instruments in polarization experiments in particle and nuclear physics. Maintaining the continuous exact parametric spin resonance condition of the equality of the spin rotator and the spin precession frequency during operation is one of the challenges. We present a detailed analytical description of the effects of detuning the exact spin resonance on the precessing vertical and in-plane components of the polarization. An important part of the formalism presented here is the consideration of experimentally relevant spin decoherence effects. Within the developed formalism, we address the impact of feedback via pilot-bunch-based comagnetometry on continuous spin flips and on the related interpretation of charged-particle electric dipole moment searches using storage rings. We propose a spin-flip-based tomography of the longitudinal profile of polarization in a bunch, which is important for the evaluation of the polarization-dependent luminosity in collider experiments. We emphasize the potential importance of the previously unexplored phase of the horizontal polarization of the envelope as an indicator of the stability of radio-frequency-driven spin rotations in storage rings and as a testing ground for spin decoherence mechanisms.

Published
2024
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2. First Search for Axionlike Particles in a Storage Ring Using a Polarized Deuteron Beam

Author

S. Karanth, E. J. Stephenson, S. P. Chang, V. Hejny, S. Park, J. Pretz, Y. K. Semertzidis, A. Wirzba, A. Wrońska, F. Abusaif, A. Aggarwal, A. Aksentev, B. Alberdi, A. Andres, L. Barion, I. Bekman, M. Beyß, C. Böhme, B. Breitkreutz, C. von Byern, N. Canale, G. Ciullo, S. Dymov, N.-O. Fröhlich, R. Gebel, K. Grigoryev, D. Grzonka, J. Hetzel, O. Javakhishvili, H. Jeong, A. Kacharava, V. Kamerdzhiev, I. Keshelashvili, A. Kononov, K. Laihem, A. Lehrach, P. Lenisa, N. Lomidze, B. Lorentz, A. Magiera, D. Mchedlishvili, F. Müller, A. Nass, N. N. Nikolaev, A. Pesce, V. Poncza, D. Prasuhn, F. Rathmann, A. Saleev, D. Shergelashvili, V. Shmakova, N. Shurkhno, S. Siddique, J. Slim, H. Soltner, R. Stassen, H. Ströher, M. Tabidze, G. Tagliente, Y. Valdau, M. Vitz, T. Wagner, and P. Wüstner

Subjects
Physics, QC1-999
Abstract

Based on the notion that the local dark-matter field of axions or axionlike particles (ALPs) in our Galaxy induces oscillating couplings to the spins of nucleons and nuclei (via the electric dipole moment of the latter and/or the paramagnetic axion-wind effect), we establish the feasibility of a new method to search for ALPs in storage rings. Based on previous work that allows us to maintain the in-plane polarization of a stored deuteron beam for a few hundred seconds, we perform a first proof-of-principle experiment at the Cooler Synchrotron (COSY) to scan momenta near 970 MeV/c. This entails a scan of the spin-precession frequency. At resonance between the spin-precession frequency of deuterons and the ALP-induced electric dipole moment (EDM) oscillation frequency, there is an accumulation of the polarization component out of the ring plane. Since the axion frequency is unknown, the momentum of the beam and, consequently, the spin-precession frequency are ramped to search for a vertical polarization change that occurs when the resonance is crossed. At COSY, four beam bunches with different polarization directions are used to make sure that no resonance is missed because of the unknown relative phase between the polarization precession and the axion or ALP field. A frequency window of 1.5 kHz width around the spin-precession frequency of 121 kHz is scanned. We describe the experimental procedure and a test of the methodology with the help of a radio-frequency Wien filter located on the COSY ring. No ALP resonance is observed. As a consequence, an upper limit of the oscillating EDM component of the deuteron as well as its axion coupling constants are provided.

Published
2023
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3. Low-energy spin-physics experiments with polarized beams and targets at the COSY storage ring

Author

P. Lenisa, F. Rathmann, L. Barion, S. Barsov, S. Bertelli, V. Carassiti, G. Ciullo, M. Contalbrigo, A. Cotta Ramusino, S. Dymov, R. Engels, D. Eversheim, R. Gebel, K. Grigoryev, J. Haidenbauer, V. Hejny, H. Jagdfeld, A. Kacharava, I. Keshelashvili, A. Kononov, T. Krings, A. Kulikov, A. Lehrach, B. Lorentz, N. Lomidze, G. Macharashvili, R. Malaguti, S. Martin, S. Merzliakov, S. Mikirtychiants, A. Nass, N.N. Nikolaev, A. Pesce, D. Prasuhn, L. Semke, S. Squerzanti, H. Soltner, M. Statera, E. Steffens, H. Ströher, M. Tabidze, G. Tagliente, P. Thörngren-Engblom, S. Trusov, Yu. Uzikov, Yu. Valdau, C. Weidemann, P. Wüstner, and P. Zupranski

Subjects
Polarized beams, Particle accelerators, Storage rings, Beam handling, Solid-state detectors, Physics, QC1-999, Optics. Light, QC350-467, Descriptive and experimental mechanics, QC120-168.85
Abstract

Abstract A low-energy spin-physics program is being developed at the COSY storage ring. To support the planned experimental activities, several experimental tools for polarized beams and targets have been developed. The paper presents the physics case and the readiness of the setup for its realization.

Published
2019
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4. New data on γ→p→→ηp with polarized photons and protons and their implications for N⁎ → Nη decays

Author

J. Müller, J. Hartmann, M. Grüner, F. Afzal, A.V. Anisovich, B. Bantes, D. Bayadilov, R. Beck, M. Becker, Y. Beloglazov, A. Berlin, M. Bichow, S. Böse, K.-T. Brinkmann, T. Challand, V. Crede, F. Dietz, M. Dieterle, P. Drexler, H. Dutz, H. Eberhardt, D. Elsner, R. Ewald, K. Fornet-Ponse, S. Friedrich, F. Frommberger, C. Funke, M. Gottschall, A. Gridnev, S. Goertz, E. Gutz, C. Hammann, V. Hannen, J. Hannappel, J. Herick, W. Hillert, P. Hoffmeister, C. Honisch, O. Jahn, T. Jude, I. Jaegle, A. Käser, D. Kaiser, H. Kalinowsky, F. Kalischewski, S. Kammer, I. Keshelashvili, P. Klassen, V. Kleber, F. Klein, E. Klempt, K. Koop, B. Krusche, M. Kube, M. Lang, I. Lopatin, Y. Maghrbi, P. Mahlberg, K. Makonyi, F. Messi, V. Metag, W. Meyer, J. Müllers, M. Nanova, V. Nikonov, D. Novinski, R. Novotny, D. Piontek, G. Reicherz, C. Rosenbaum, T. Rostomyan, B. Roth, A. Sarantsev, C. Schmidt, H. Schmieden, R. Schmitz, T. Seifen, V. Sokhoyan, A. Thiel, U. Thoma, M. Urban, H. van Pee, D. Walther, C. Wendel, U. Wiedner, A. Wilson, A. Winnebeck, and L. Witthauer

Subjects
Physics, QC1-999
Abstract

The polarization observables T,E,P,H, and G in photoproduction of η mesons off protons are measured for photon energies from threshold to W=2400 MeV (T), 2280 MeV (E), 1620 MeV (P,H), or 1820 MeV (G), covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, JüBo, and BnGa partial-wave analyses. A refit within the BnGa approach including further data yields precise branching ratios for the Nη decay of nucleon resonances. A Nη-branching ratio of 0.33±0.04 for N(1650)1/2− is found, which reduces the large and controversially discussed Nη-branching ratio difference of the two lowest mass JP=1/2−-resonances significantly. Keywords: Baryon spectroscopy, Meson photoproduction, Polarization observables

Published
2020
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5. Measurement of the beam-helicity asymmetry in photoproduction of π0η pairs on carbon, aluminum, and lead

Author

V. Sokhoyan, S. Prakhov, A. Fix, S. Abt, P. Achenbach, P. Adlarson, F. Afzal, P. Aguar-Bartolomé, Z. Ahmed, K. Altangerel, J.R.M. Annand, H.J. Arends, K. Bantawa, M. Bashkanov, R. Beck, M. Biroth, N.S. Borisov, A. Braghieri, W.J. Briscoe, S. Cherepnya, F. Cividini, C. Collicott, S. Costanza, A. Denig, M. Dieterle, E.J. Downie, P. Drexler, M.I. Ferretti Bondy, L.V. Fil'kov, S. Gardner, S. Garni, D.I. Glazier, I. Gorodnov, W. Gradl, M. Günther, G.M. Gurevich, L. Heijkenskjöld, D. Hornidge, G.M. Huber, A. Käser, V.L. Kashevarov, S. Kay, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, A. Lazarev, K. Livingston, S. Lutterer, I.J.D. MacGregor, R. Macrae, D.M. Manley, P.P. Martel, J.C. McGeorge, D.G. Middleton, R. Miskimen, E. Mornacchi, C. Mullen, A. Mushkarenkov, A. Neganov, A. Neiser, M. Oberle, M. Ostrick, P.B. Otte, D. Paudyal, P. Pedroni, A. Powell, E. Rickert, G. Ron, T. Rostomyan, A. Sarty, C. Sfienti, K. Spieker, O. Steffen, I.I. Strakovsky, B. Strandberg, Th. Strub, I. Supek, A. Thiel, M. Thiel, A. Thomas, M. Unverzagt, Yu.A. Usov, S. Wagner, N.K. Walford, D.P. Watts, D. Werthmüller, J. Wettig, L. Witthauer, M. Wolfes, and N. Zachariou

Subjects
Physics, QC1-999
Abstract

The beam-helicity asymmetry was measured, for the first time, in photoproduction of π0η pairs on carbon, aluminum, and lead, with the A2 experimental setup at MAMI. The results are compared to an earlier measurement on a free proton and to the corresponding theoretical calculations. The Mainz model is used to predict the beam-helicity asymmetry for the nuclear targets. The present results indicate that the photoproduction mechanism for π0η pairs on nuclei is similar to photoproduction on a free nucleon. This process is dominated by the D33 partial wave with the ηΔ(1232) intermediate state.

Published
2020
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6. First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons

Author

A. Käser, M. Dieterle, L. Witthauer, S. Abt, P. Achenbach, P. Adlarson, F. Afzal, Z. Ahmed, J. Ahrens, J.R.M. Annand, H.J. Arends, M. Bashkanov, R. Beck, M. Biroth, N.S. Borisov, A. Braghieri, W.J. Briscoe, F. Cividini, C. Collicott, S. Costanza, A. Denig, E.J. Downie, P. Drexler, A. Fix, S. Garni, D.I. Glazier, I. Gorodnov, W. Gradl, M. Günther, G.M. Gurevich, L. Heijkenskjöld, D. Hornidge, G.M. Huber, V.L. Kashevarov, S. Kay, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, A.B. Lazarev, V. Lisin, K. Livingston, S. Lutterer, I.J.D. MacGregor, D.M. Manley, P.P. Martel, V. Metag, W. Meyer, R. Miskimen, E. Mornacchi, A. Mushkarenkov, A.B. Neganov, A. Neiser, M. Oberle, M. Ostrick, P.B. Otte, D. Paudyal, P. Pedroni, A. Polonski, S.N. Prakhov, G. Reicherz, G. Ron, T. Rostomyan, A. Sarty, C. Sfienti, V. Sokhoyan, K. Spieker, O. Steffen, I.I. Strakovsky, Th. Strub, I. Supek, A. Thiel, M. Thiel, A. Thomas, M. Unverzagt, Yu.A. Usov, S. Wagner, N.K. Walford, D.P. Watts, D. Werthmüller, J. Wettig, M. Wolfes, and L. Zana

Subjects
Physics, QC1-999
Abstract

The helicity-dependent cross sections for the photoproduction of π0η pairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball – TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the σ1/2 (photon and target spin antiparallel) and σ3/2 (parallel spins) components to be measured for quasi-free production of π0η pairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant protons and neutrons. The absolute couplings for protons and neutrons are also identical. This means that nucleon resonances contributing to this reaction in the investigated energy range have almost equal electromagnetic helicity couplings, A1/2n,p and A3/2n,p. Identical couplings for protons and neutrons are typical for Δ resonances and identical A1/2 and A3/2 components are only possible for J≥3/2 states, which constrains possible contributions of nucleon resonances.

Published
2018
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7. First measurement of the polarization observable E and helicity-dependent cross sections in single π0 photoproduction from quasi-free nucleons

Author

M. Dieterle, L. Witthauer, F. Cividini, S. Abt, P. Achenbach, P. Adlarson, F. Afzal, Z. Ahmed, C.S. Akondi, J.R.M. Annand, H.J. Arends, M. Bashkanov, R. Beck, M. Biroth, N.S. Borisov, A. Braghieri, W.J. Briscoe, S. Costanza, C. Collicott, A. Denig, E.J. Downie, P. Drexler, M.I. Ferretti-Bondy, S. Gardner, S. Garni, D.I. Glazier, D. Glowa, W. Gradl, M. Günther, G.M. Gurevich, D. Hamilton, D. Hornidge, G.M. Huber, A. Käser, V.L. Kashevarov, S. Kay, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, A.B. Lazarev, J.M. Linturi, V. Lisin, K. Livingston, S. Lutterer, I.J.D. MacGregor, J. Mancell, D.M. Manley, P.P. Martel, V. Metag, W. Meyer, R. Miskimen, E. Mornacchi, A. Mushkarenkov, A.B. Neganov, A. Neiser, M. Oberle, M. Ostrick, P.B. Otte, D. Paudyal, P. Pedroni, A. Polonski, S.N. Prakhov, A. Rajabi, G. Reicherz, G. Ron, T. Rostomyan, A. Sarty, C. Sfienti, M.H. Sikora, V. Sokhoyan, K. Spieker, O. Steffen, I.I. Strakovsky, Th. Strub, I. Supek, A. Thiel, M. Thiel, A. Thomas, M. Unverzagt, Yu.A. Usov, S. Wagner, N.K. Walford, D.P. Watts, D. Werthmüller, J. Wettig, M. Wolfes, and L. Zana

Subjects
Physics, QC1-999
Abstract

The double-polarization observable E and the helicity-dependent cross sections σ1/2 and σ3/2 have been measured for the first time for single π0 photoproduction from protons and neutrons bound in the deuteron at the electron accelerator facility MAMI in Mainz, Germany. The experiment used a circularly polarized photon beam and a longitudinally polarized deuterated butanol target. The reaction products, recoil nucleons and decay photons from the π0 meson were detected with the Crystal Ball and TAPS electromagnetic calorimeters. Effects from nuclear Fermi motion were removed by a kinematic reconstruction of the π0N final state. A comparison to data measured with a free proton target showed that the absolute scale of the cross sections is significantly modified by nuclear final-state interaction (FSI) effects. However, there is no significant effect on the asymmetry E since the σ1/2 and σ3/2 components appear to be influenced in a similar way. Thus, the best approximation of the two helicity-dependent cross sections for the free neutron is obtained by combining the asymmetry E measured with quasi-free neutrons and the unpolarized cross section corrected for FSI effects under the assumption that the FSI effects are similar for neutrons and protons.

Published
2017
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8. Measurement of the absolute differential cross section of proton–proton elastic scattering at small angles

Author

D. Mchedlishvili, D. Chiladze, S. Dymov, Z. Bagdasarian, S. Barsov, R. Gebel, B. Gou, M. Hartmann, A. Kacharava, I. Keshelashvili, A. Khoukaz, P. Kulessa, A. Kulikov, A. Lehrach, N. Lomidze, B. Lorentz, R. Maier, G. Macharashvili, S. Merzliakov, S. Mikirtychyants, M. Nioradze, H. Ohm, D. Prasuhn, F. Rathmann, V. Serdyuk, D. Schroer, V. Shmakova, R. Stassen, H.J. Stein, H. Stockhorst, I.I. Strakovsky, H. Ströher, M. Tabidze, A. Täschner, S. Trusov, D. Tsirkov, Yu. Uzikov, Yu. Valdau, C. Wilkin, R.L. Workman, and P. Wüstner

Subjects
Physics, QC1-999
Abstract

The differential cross section for proton–proton elastic scattering has been measured at a beam kinetic energy of 1.0 GeV and in 200 MeV steps from 1.6 to 2.8 GeV for centre-of-mass angles in the range from 12°–16° to 25°–30°, depending on the energy. A precision in the overall normalisation of typically 3% was achieved by studying the energy losses of the circulating beam of the COSY storage ring as it passed repeatedly through the windowless hydrogen target of the ANKE magnetic spectrometer. It is shown that the data have a significant impact upon the results of a partial wave analysis. After extrapolating the differential cross sections to the forward direction, the results are broadly compatible with the predictions of forward dispersion relations. Keywords: Proton–proton elastic scattering, Differential cross section

Published
2016
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9. Threshold π0 photoproduction on transverse polarised protons at MAMI

Author

S. Schumann, P.B. Otte, C.S. Akondi, J.R.M. Annand, H.-J. Arends, R. Beck, A.M. Bernstein, N. Borisov, A. Braghieri, W.J. Briscoe, S. Cherepnya, C. Collicott, S. Costanza, E.J. Downie, M. Dieterle, C. Fernández-Ramírez, A. Fix, L.V. Fil'kov, S. Garni, D.I. Glazier, W. Gradl, G. Gurevich, P. Hall-Barrientos, D. Hamilton, D. Hornidge, D. Howdle, G.M. Huber, V.L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, A. Lazarev, V. Lisin, K. Livingston, I.J.D. MacGregor, J. Mancel, D.M. Manley, P.P. Martel, E.F. McNicoll, W. Meyer, D. Middleton, R. Miskimen, A. Mushkarenkov, B.M.K. Nefkens, A. Neganov, A. Nikolaev, M. Oberle, M. Ostrick, H. Ortega, P. Ott, B. Oussena, D. Paudyal, P. Pedroni, A. Polonski, V.V. Polyanski, S. Prakhov, G. Reicherz, T. Rostomyan, A. Sarty, M.H. Sikora, V. Sokhoyan, O. Steffen, I.I. Strakovsky, Th. Strub, I. Supek, L. Tiator, A. Thomas, M. Unverzagt, Yu.A. Usov, D.P. Watts, D. Werthmüller, L. Witthauer, and M. Wolfes

Subjects
Threshold π0 photoproduction, Target asymmetry, Electromagnetic multipoles, Physics, QC1-999
Abstract

Polarisation-dependent differential cross sections σT associated with the target asymmetry T have been measured for the reaction γp→→pπ0 with transverse target polarisation from π0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ball / TAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for σT have been used in combination with our previous measurements of the unpolarised cross section σ0 and the beam asymmetry Σ for a model-independent determination of S- and P-wave multipoles in the π0 threshold region, which includes for the first time a direct determination of the imaginary part of the E0+ multipole.

Published
2015
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10. Measurement of double polarisation asymmetries in ω-photoproduction

Author

H. Eberhardt, T.C. Jude, H. Schmieden, A.V. Anisovich, B. Bantes, D. Bayadilov, R. Beck, Yu. Beloglazov, M. Bichow, S. Böse, K.-Th. Brinkmann, Th. Challand, V. Crede, F. Diez, P. Drexler, H. Dutz, D. Elsner, R. Ewald, K. Fornet-Ponse, St. Friedrich, F. Frommberger, Ch. Funke, M. Gottschall, A. Gridnev, M. Grüner, E. Gutz, Ch. Hammann, J. Hannappel, J. Hartmann, W. Hillert, Ph. Hoffmeister, Ch. Honisch, I. Jaegle, D. Kaiser, H. Kalinowsky, F. Kalischewski, S. Kammer, I. Keshelashvili, V. Kleber, F. Klein, E. Klempt, K. Koop, B. Krusche, M. Kube, M. Lang, I. Lopatin, Y. Maghrbi, K. Makonyi, V. Metag, W. Meyer, J. Müller, M. Nanova, V. Nikonov, R. Novotny, D. Piontek, S. Reeve, G. Reicherz, T. Rostomyan, S. Runkel, A. Sarantsev, St. Schaepe, Ch. Schmidt, R. Schmitz, T. Seifen, V. Sokhoyan, V. Sumachev, A. Thiel, U. Thoma, M. Urban, H. van Pee, D. Walther, Ch. Wendel, U. Wiedner, A. Wilson, and A. Winnebeck

Subjects
Meson production, Polarisation in interactions and scattering, Light mesons (SCB0), Physics, QC1-999
Abstract

The first measurements of the beam-target-helicity-asymmetries E and G in the photoproduction of ω-mesons off protons at the CBELSA/TAPS experiment are reported. E (G) was measured using circularly (linearly) polarised photons and a longitudinally polarised target. E was measured over the photon energy range from close to threshold (Eγ=1108 MeV) to Eγ=2300 MeV and G at a single energy interval of 1108

Published
2015
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11. The isospin structure of photoproduction of πη pairs from the nucleon in the threshold region

Author

A. Käser, J. Ahrens, J.R.M. Annand, H.J. Arends, K. Bantawa, P.A. Bartolome, R. Beck, V. Bekrenev, H. Berghäuser, A. Braghieri, D. Branford, W.J. Briscoe, J. Brudvik, S. Cherepnya, S. Costanza, B. Demissie, M. Dieterle, E.J. Downie, P. Drexler, L.V. Fil'kov, A. Fix, D.I. Glazier, D. Hamilton, E. Heid, D. Hornidge, D. Howdle, G.M. Huber, O. Jahn, I. Jaegle, T.C. Jude, V.L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, S.P. Kruglov, B. Krusche, V. Lisin, K. Livingston, I.J.D. MacGregor, Y. Maghrbi, J. Mancell, D.M. Manley, Z. Marinides, J.C. McGeorge, E. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D.G. Middleton, A. Mushkarenkov, A. Nikolaev, R. Novotny, M. Oberle, M. Ostrick, P. Otte, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S.N. Prakhov, J. Robinson, G. Rosner, T. Rostomyan, S. Schumann, M.H. Sikora, D.I. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D.P. Watts, D. Werthmüller, and L. Witthauer

Subjects
Physics, QC1-999
Abstract

Photoproduction of πη-pairs from nucleons has been investigated from threshold up to incident photon energies of ≈ 1.4 GeV. The quasi-free reactions γp→pπ0η, γn→nπ0η, γp→nπ+η, and γn→pπ−η were for the first time measured from nucleons bound in the deuteron. The corresponding reactions from a free-proton target were also studied to investigate final-state interaction effects (for neutral pions the free-proton results could be compared to previous measurements; the γp→nπ+η reaction was measured for the first time). For the π0η final state coherent production via the γd→dπ0η reaction was also investigated. The experiments were performed at the tagged photon beam of the Mainz MAMI accelerator using an almost 4π coverage electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. The total cross sections for the four different final states obey the relation σ(pπ0η)≈σ(nπ0η)≈2σ(pπ−η)≈2σ(nπ+η) as expected for a dominant contribution from a Δ⋆→ηΔ(1232)→πηN reaction chain, which is also supported by the shapes of the invariant-mass distributions of nucleon–meson and π–η pairs. The experimental results are compared to the predictions from an isobar reaction model.

Published
2015
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12. The polarization observables T, P, and H and their impact on γp→pπ0 multipoles

Author

J. Hartmann, H. Dutz, A.V. Anisovich, D. Bayadilov, R. Beck, M. Becker, Y. Beloglazov, A. Berlin, M. Bichow, S. Böse, K.-Th. Brinkmann, V. Crede, M. Dieterle, H. Eberhardt, D. Elsner, K. Fornet-Ponse, St. Friedrich, F. Frommberger, Ch. Funke, M. Gottschall, A. Gridnev, M. Grüner, St. Goertz, E. Gutz, Ch. Hammann, J. Hannappel, V. Hannen, J. Herick, W. Hillert, Ph. Hoffmeister, Ch. Honisch, O. Jahn, T. Jude, A. Käser, D. Kaiser, H. Kalinowsky, F. Kalischewski, P. Klassen, I. Keshelashvili, F. Klein, E. Klempt, K. Koop, B. Krusche, M. Kube, M. Lang, I. Lopatin, K. Makonyi, F. Messi, V. Metag, W. Meyer, J. Müller, M. Nanova, V. Nikonov, D. Novinski, R. Novotny, D. Piontek, S. Reeve, Ch. Rosenbaum, B. Roth, G. Reicherz, T. Rostomyan, St. Runkel, A. Sarantsev, Ch. Schmidt, H. Schmieden, R. Schmitz, T. Seifen, V. Sokhoyan, Ph. Thämer, A. Thiel, U. Thoma, M. Urban, H. van Pee, D. Walther, Ch. Wendel, U. Wiedner, A. Wilson, A. Winnebeck, and L. Witthauer

Subjects
Baryon spectroscopy, Meson photoproduction, Polarization observables, Multipoles, Physics, QC1-999
Abstract

Data on the polarization observables T, P, and H for the reaction γp→pπ0 are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction.

Published
2015
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13. Measurement of the analysing power in proton–proton elastic scattering at small angles

Author

Z. Bagdasarian, D. Chiladze, S. Dymov, A. Kacharava, G. Macharashvili, S. Barsov, R. Gebel, B. Gou, M. Hartmann, I. Keshelashvili, A. Khoukaz, P. Kulessa, A. Kulikov, A. Lehrach, N. Lomidze, B. Lorentz, R. Maier, D. Mchedlishvili, S. Merzliakov, S. Mikirtychyants, M. Nioradze, H. Ohm, M. Papenbrock, D. Prasuhn, F. Rathmann, V. Serdyuk, V. Shmakova, R. Stassen, H. Stockhorst, I.I. Strakovsky, H. Ströher, M. Tabidze, A. Täschner, S. Trusov, D. Tsirkov, Yu. Uzikov, Yu. Valdau, C. Wilkin, and R.L. Workman

Subjects
Physics, QC1-999
Abstract

The proton analysing power in p→p elastic scattering has been measured at small angles at COSY-ANKE at 796 MeV and five other beam energies between 1.6 and 2.4 GeV using a polarised proton beam. The asymmetries obtained by detecting the fast proton in the ANKE forward detector or the slow recoil proton in a silicon tracking telescope are completely consistent. Although the analysing power results agree well with the many published data at 796 MeV, and also with the most recent partial wave solution at this energy, the ANKE data at the higher energies lie well above the predictions of this solution at small angles. An updated phase shift analysis that uses the ANKE results together with the World data leads to a much better description of these new measurements. Keywords: Proton–proton elastic scattering, Analysing power, Phase shift analysis

Published
2014
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14. Experimental constraints on the ω–nucleus real potential

Author

S. Friedrich, K. Makonyi, V. Metag, D. Bayadilov, B. Bantes, R. Beck, Y.A. Beloglazov, S. Böse, K.-T. Brinkmann, Th. Challand, V. Crede, T. Dahlke, F. Dietz, P. Drexler, H. Eberhardt, D. Elsner, R. Ewald, K. Fornet-Ponse, F. Frommberger, Ch. Funke, M. Gottschall, A. Gridnev, M. Grüner, E. Gutz, Ch. Hammann, D. Hammann, J. Hannappel, J. Hartmann, W. Hillert, S. Hirenzaki, P. Hoffmeister, Ch. Honisch, I. Jaegle, D. Kaiser, H. Kalinowsky, S. Kammer, I. Keshelashvili, V. Kleber, F. Klein, B. Krusche, M. Lang, I.V. Lopatin, Y. Maghrbi, M. Nanova, H. Nagahiro, J. Müller, T. Odenthal, D. Piontek, T. Rostomyan, S. Schaepe, Ch. Schmidt, H. Schmieden, R. Schmitz, T. Seifen, A. Thiel, U. Thoma, H. van Pee, D. Walther, J. Weil, Ch. Wendel, U. Wiedner, A. Wilson, A. Winnebeck, and F. Zenke

Subjects
Physics, QC1-999
Abstract

In a search for ω mesic states, the production of ω-mesons in coincidence with forward going protons has been studied in photon induced reactions on 12C for incident photon energies of 1250–3100 MeV. The π0γ pairs from decays of bound or quasi-free ω-mesons have been measured with the CBELSA/TAPS detector system in coincidence with protons registered in the MiniTAPS forward array. Structures in the total energy distribution of the π0γ pairs, which would indicate the population and decay of bound ω 11B states, are not observed. The π0γ cross section of 0.3 nb MeV−1 sr−1 observed in the bound state energy regime between −100 and 0 MeV may be accounted for by yield leaking into the bound state regime because of the large in-medium width of the ω-meson. A comparison of the measured total energy distribution with calculations suggests the real part V0 of the ω 11B potential to be small and only weakly attractive with V0(ρ=ρ0)=−15±35(stat)±20(syst) MeV in contrast to some theoretical predictions of attractive potentials with a depth of 100–150 MeV.

Published
2014
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15. Phase measurement for driven spin oscillations in a storage ring

Author

N. Hempelmann, V. Hejny, J. Pretz, H. Soltner, W. Augustyniak, Z. Bagdasarian, M. Bai, L. Barion, M. Berz, S. Chekmenev, G. Ciullo, S. Dymov, D. Eversmann, M. Gaisser, R. Gebel, K. Grigoryev, D. Grzonka, G. Guidoboni, D. Heberling, J. Hetzel, F. Hinder, A. Kacharava, V. Kamerdzhiev, I. Keshelashvili, I. Koop, A. Kulikov, A. Lehrach, P. Lenisa, N. Lomidze, B. Lorentz, P. Maanen, G. Macharashvili, A. Magiera, D. Mchedlishvili, S. Mey, F. Müller, A. Nass, N. N. Nikolaev, M. Nioradze, A. Pesce, D. Prasuhn, F. Rathmann, M. Rosenthal, A. Saleev, V. Schmidt, Y. Semertzidis, Y. Senichev, V. Shmakova, A. Silenko, J. Slim, A. Stahl, R. Stassen, E. Stephenson, H. Stockhorst, H. Ströher, M. Tabidze, G. Tagliente, R. Talman, P. Thörngren Engblom, F. Trinkel, Yu. Uzikov, Yu. Valdau, E. Valetov, A. Vassiliev, C. Weidemann, A. Wrońska, P. Wüstner, P. Zuprański, and M. Żurek

Subjects
Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

This paper reports the first simultaneous measurement of the horizontal and vertical components of the polarization vector in a storage ring under the influence of a radio frequency (rf) solenoid. The experiments were performed at the Cooler Synchrotron COSY in Jülich using a vector polarized, bunched 0.97 GeV/c deuteron beam. Using the new spin feedback system, we set the initial phase difference between the solenoid field and the precession of the polarization vector to a predefined value. The feedback system was then switched off, allowing the phase difference to change over time, and the solenoid was switched on to rotate the polarization vector. We observed an oscillation of the vertical polarization component and the phase difference. The oscillations can be described using an analytical model. The results of this experiment also apply to other rf devices with horizontal magnetic fields, such as Wien filters. The precise manipulation of particle spins in storage rings is a prerequisite for measuring the electric dipole moment (EDM) of charged particles.

Published
2018
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16. Connection between zero chromaticity and long in-plane polarization lifetime in a magnetic storage ring

Author

G. Guidoboni, E. J. Stephenson, A. Wrońska, Z. Bagdasarian, J. Bsaisou, S. Chekmenev, G. Ciullo, S. Dymov, D. Eversmann, M. Gaisser, R. Gebel, V. Hejny, N. Hempelmann, F. Hinder, A. Kacharava, I. Keshelashvili, P. Kulessa, P. Lenisa, A. Lehrach, B. Lorentz, P. Maanen, R. Maier, D. Mchedlishvili, S. Mey, A. Nass, A. Pesce, Y. Orlov, J. Pretz, D. Prasuhn, F. Rathmann, M. Rosenthal, A. Saleev, Y. K. Semertzidis, Y. Senichev, V. Shmakova, H. Stockhorst, H. Ströher, R. Talman, P. Thörngren Engblom, F. Trinkel, Yu. Valdau, C. Weidemann, P. Wüstner, M. Żurek, and D. Zyuzin

Subjects
Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

In this paper, we demonstrate the connection between a magnetic storage ring with additional sextupole fields set so that the x and y chromaticities vanish and the maximizing of the lifetime of in-plane polarization (IPP) for a 0.97-GeV/c deuteron beam. The IPP magnitude was measured by continuously monitoring the down-up scattering asymmetry (sensitive to sideways polarization) in an in-beam, carbon-target polarimeter and unfolding the precession of the IPP due to the magnetic anomaly of the deuteron. The optimum operating conditions for a long IPP lifetime were made by scanning the field of the storage ring sextupole magnet families while observing the rate of IPP loss during storage of the beam. The beam was bunched and electron cooled. The IPP losses appear to arise from the change of the orbit circumference, and consequently the particle speed and spin tune, due to the transverse betatron oscillations of individual particles in the beam. The effects of these changes are canceled by an appropriate sextupole field setting.

Published
2018
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17. Observation of a structure in the $$M_{p\eta }$$ invariant mass distribution near 1700 $$\hbox {MeV}/\hbox {c}^2$$ in the $$\gamma \mathbf {p \rightarrow p \pi ^0 \eta } $$ reaction

Author

V. Metag, M. Nanova, J. Hartmann, P. Mahlberg, F. Afzal, C. Bartels, D. Bayadilov, R. Beck, M. Becker, E. Blanke, K.-T. Brinkmann, S. Ciupka, V. Crede, M. Dieterle, H. Dutz, D. Elsner, F. Frommberger, A. Gridnev, M. Gottschall, M. Grüner, Ch. Hammann, J. Hannappel, W. Hillert, J. Hoff, Ph. Hoffmeister, Ch. Honisch, T. Jude, H. Kalinowsky, F. Kalischewski, I. Keshelashvili, B. Ketzer, P. Klassen, F. Klein, K. Koop, P. Kroenert, B. Krusche, M. Lang, I. Lopatin, F. Messi, W. Meyer, B. Mitlasóczky, J. Müller, J. Müllers, V. Nikonov, V. Novinsky, R. Novotny, D. Piontek, G. Reicherz, L. Richter, T. Rostomyan, S. Runkel, B. Salisbury, A. Sarantsev, D. Schaab, Ch. Schmidt, H. Schmieden, J. Schultes, T. Seifen, V. Sokhoyan, C. Sowa, K. Spieker, N. Stausberg, A. Thiel, U. Thoma, T. Triffterer, M. Urban, G. Urff, H. van Pee, M. Wagner, D. Walther, Ch. Wendel, D. Werthmüller, U. Wiedner, A. Wilson, A. Winnebeck, L. Witthauer, and Y. Wunderlich

Subjects
Nuclear and High Energy Physics
Published
2021
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18. Spin tune mapping as a novel tool to probe the spin dynamics in storage rings

Author

A. Saleev, N. N. Nikolaev, F. Rathmann, W. Augustyniak, Z. Bagdasarian, M. Bai, L. Barion, M. Berz, S. Chekmenev, G. Ciullo, S. Dymov, D. Eversmann, M. Gaisser, R. Gebel, K. Grigoryev, D. Grzonka, G. Guidoboni, D. Heberling, V. Hejny, N. Hempelmann, J. Hetzel, F. Hinder, A. Kacharava, V. Kamerdzhiev, I. Keshelashvili, I. Koop, A. Kulikov, A. Lehrach, P. Lenisa, N. Lomidze, B. Lorentz, P. Maanen, G. Macharashvili, A. Magiera, D. Mchedlishvili, S. Mey, F. Müller, A. Nass, A. Pesce, D. Prasuhn, J. Pretz, M. Rosenthal, V. Schmidt, Y. Semertzidis, Y. Senichev, V. Shmakova, A. Silenko, J. Slim, H. Soltner, A. Stahl, R. Stassen, E. Stephenson, H. Stockhorst, H. Ströher, M. Tabidze, G. Tagliente, R. Talman, P. Thörngren Engblom, F. Trinkel, Yu. Uzikov, Yu. Valdau, E. Valetov, A. Vassiliev, C. Weidemann, A. Wrońska, P. Wüstner, P. Zuprański, and M. Zurek

Subjects
Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Precision experiments, such as the search for electric dipole moments of charged particles using storage rings, demand for an understanding of the spin dynamics with unprecedented accuracy. The ultimate aim is to measure the electric dipole moments with a sensitivity up to 15 orders in magnitude better than the magnetic dipole moment of the stored particles. This formidable task requires an understanding of the background to the signal of the electric dipole from rotations of the spins in the spurious magnetic fields of a storage ring. One of the observables, especially sensitive to the imperfection magnetic fields in the ring is the angular orientation of stable spin axis. Up to now, the stable spin axis has never been determined experimentally, and in addition, the JEDI collaboration for the first time succeeded to quantify the background signals that stem from false rotations of the magnetic dipole moments in the horizontal and longitudinal imperfection magnetic fields of the storage ring. To this end, we developed a new method based on the spin tune response of a machine to artificially applied longitudinal magnetic fields. This novel technique, called spin tune mapping, emerges as a very powerful tool to probe the spin dynamics in storage rings. The technique was experimentally tested in 2014 using polarized deuterons stored in the cooler synchrotron COSY, and for the first time, the angular orientation of the stable spin axis at two different locations in the ring has been determined to an unprecedented accuracy of better than 2.8 μ rad.

Published
2017
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19. Measurement of the helicity asymmetry E for the reaction $$ \gamma p\rightarrow \pi ^0 p$$

Author

H. Schmieden, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, T. Rostomyan, M. Gottschall, M. Urban, V. Sokhoyan, D. Walther, M. Dieterle, T. Seifen, Ch. Hammann, A. Thiel, A. Winnebeck, Frank Frommberger, Matthew Lang, M. Kube, I. Keshelashvili, J. Hannappel, A. V. Anisovich, Jörg H. Müller, Jens Hartmann, V. Crede, Lilian Witthauer, Ulrich Wiedner, U. Thoma, P. Mahlberg, G. Reicherz, Frank Klein, V. Metag, Y. Wunderlich, K. Koop, K. Spieker, A. V. Sarantsev, A. Wilson, M. Bichow, Ch. Honisch, Ch. Schmidt, S. Friedrich, K. Makonyi, R. Beck, H. Dutz, K.-Th. Brinkmann, H. van Pee, P. Klassen, H. Eberhardt, D. Werthmüller, M. Grüner, S. Kammer, F. Dietz, R. Ewald, F. Afzal, H. Kalinowsky, E. Gutz, D. Piontek, I. V. Lopatin, T. C. Jude, Wolfgang Hillert, Ch. Wendel, D. Elsner, R. W. Novotny, Ph. Hoffmeister, V. A. Nikonov, J. Müllers, Eberhard Klempt, B. Krusche, W. Meyer, and K. Fornet-Ponse

Subjects
Nuclear physics, Physics, Nuclear and High Energy Physics, Photon, media_common.quotation_subject, Hadron, Bremsstrahlung, Nuclear fusion, Electron, Photon energy, Helicity, Asymmetry, media_common
Abstract

A measurement of the double-polarization observable E for the reaction $$\gamma p\rightarrow \pi ^0 p$$ γ p → π 0 p is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C$$_4$$ 4 H$$_9$$ 9 OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from $$E_\gamma =600$$ E γ = 600 to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.

Published
2021
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20. Beam-based alignment at the Cooler Synchrotron COSY as a prerequisite for an electric dipole moment measurement

Author

T. Wagner, A. Nass, J. Pretz, F. Abusaif, A. Aggarwal, A. Andres, I. Bekman, N. Canale, I. Ciepal, G. Ciullo, F. Dahmen, S. Dymov, C. Ehrlich, R. Gebel, K. Grigoryev, D. Grzonka, V. Hejny, J. Hetzel, A. Kacharava, V. Kamerdzhiev, S. Karanth, I. Keshelashvili, A. Kononov, A. Kulikov, K. Laihem, A. Lehrach, P. Lenisa, N. Lomidze, A. Magiera, D. Mchedlishvili, F. Müller, N.N. Nikolaev, A. Pesce, V.

Published
2021
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21. Observation of the pη′ Cusp in the New Precise Beam Asymmetry Σ Data for γp→pη

Author

Cbelsa, F. Afzal, L Richter, S. Ciupka, U-G Meißner, V. Metag, W. Meyer, M. Grüner, K. Koop, T. Seifen, Lilian Witthauer, H. Kalinowsky, Matthew Lang, D. Piontek, N. Stausberg, M. Urban, I. V. Lopatin, A. V. Sarantsev, T. C. Jude, Frank Frommberger, M. Becker, B. Mitlasóczki, H. Schmieden, M. Dieterle, V. Sokhoyan, H. van Pee, D. E. Bayadilov, P. Klassen, K. Spieker, K. Nikonov, B. Krusche, A. B. Gridnev, Mariana Nanova, B. Salisbury, Wolfgang Hillert, J. Hannappel, C. Sowa, J. Hoff, E. Gutz, Ch. Honisch, J. Schultes, H. Dutz, G. Urff, Ch. Schmidt, Y. Wunderlich, Ulrich Wiedner, Frank Klein, V. Crede, U. Thoma, D. Elsner, S. Friedrich, A. Wilson, R. W. Novotny, Ph. Hoffmeister, A. Thiel, V. Novinskiy, P. Mahlberg, A. V. Anisovich, Francesco Messi, I. Keshelashvili, Ch. Wendel, F. Kalischewski, K.-T. Brinkmann, T. Triffterer, P. Kroenert, G. Reicherz, D. Walther, Jörg H. Müller, Jens Hartmann, D. Rönchen, T. Rostomyan, M. Gottschall, E. Blanke, D. Schaab, R. Beck, Ch. Hammann, A. Winnebeck, J. Müllers, Eberhard Klempt, and V. A. Nikonov

Subjects
Physics, Photon, Meson, media_common.quotation_subject, Partial wave analysis, Nuclear Theory, Solid angle, General Physics and Astronomy, Observable, Polarization (waves), 01 natural sciences, Asymmetry, Nuclear physics, 0103 physical sciences, Physics::Accelerator Physics, Nuclear Experiment, 010306 general physics, Nucleon, media_common
Abstract

Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W=1748 MeV to W=2045 MeV). The data cover the full solid angle that allows for a precise moment analysis. For the first time, a strong cusp effect in a polarization observable has been observed that is an effect of a branch-point singularity at the pη^{'} threshold [E_{γ}=1447 MeV (W=1896 MeV)]. The latest BnGa partial wave analysis includes the new beam asymmetry data and yields a strong indication for the N(1895)1/2^{-} nucleon resonance, demonstrating the importance of including all singularities for a correct determination of partial waves and resonance parameters.

Published
2020
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22. Extracting the spin polarizabilities of the proton by measurement of Compton double-polarization observables

Author

Susanna Costanza, A. G. Denig, V. L. Kashevarov, V. Metag, C. Sfienti, W. Gradl, G. M. Huber, M. Oberle, D. Werthmüller, J. Wettig, M. Biroth, F. Afzal, P. B. Otte, V. Lisin, A. Polonski, V. Sokhoyan, A. B. Lazarev, Anthony W. Thomas, D. I. Glazier, K. Livingston, S. Lutterer, K. Spieker, J. Mancell, S. Gardner, N. S. Borisov, A. Käser, D. Hornidge, C. Collicott, A. Braghieri, A. B. Neganov, Th. Strub, A. Rajabi, D. P. Watts, Patrick Achenbach, J. R. M. Annand, H. J. Arends, P. Drexler, M. Ostrick, R. Kondratiev, Michaela Thiel, Lena Heijkenskjöld, M. I. Ferretti-Bondy, D. Glowa, M. Bashkanov, R. A. Miskimen, M. Korolija, S. N. Prakhov, Yu. A. Usov, O. Steffen, A. Thiel, G. M. Gurevich, David Manley, P. Pedroni, Lorenzo Zana, P. P. Martel, S. Garni, A. Neiser, I. Keshelashvili, David Hamilton, W. Meyer, B. Krusche, J. Linturi, M. Dieterle, Lilian Witthauer, S. Kay, S. Günther, S. Wagner, G. Reicherz, S. Abt, C. S. Akondi, A. J. Sarty, Reinhard Beck, I. Supek, I. Gorodnov, M. H. Sikora, Roderick M. Macrae, W. J. Briscoe, A. N. Mushkarenkov, T. Rostomyan, Guy Ron, E. J. Downie, M. Unverzagt, F. Cividini, P. Adlarson, Z. Ahmed, I. I. Strakovsky, C. Mullen, Durga Paudyal, M. Wolfes, A. Powell, N. K. Walford, E. Mornacchi, and I. J. D. MacGregor

Subjects
Nuclear reaction, Physics, Chiral perturbation theory, Proton, 010308 nuclear & particles physics, Resonance, 16. Peace & justice, 01 natural sciences, Baryon, 0103 physical sciences, Proton spin crisis, Atomic physics, 010306 general physics, Microtron, Spin-½
Abstract

The Compton double-polarization observable \ud Σ\ud 2\ud z\ud has been measured for the first time in the \ud Δ\ud (\ud 1232\ud )\ud resonance region using a circularly polarized photon beam incident on a longitudinally polarized proton target at the Mainz Microtron. This paper reports these results, together with the model-dependent extraction of four proton spin polarizabilities from fits to additional asymmetry data using either a dispersion relation calculation or a baryon chiral perturbation theory calculations with the weighted average of these two fits resulting in \ud γ\ud E\ud 1\ud E\ud 1\ud =\ud −\ud 2.87\ud ±\ud 0.52\ud ,\ud \ud γ\ud M\ud 1\ud M\ud 1\ud =\ud 2.70\ud ±\ud 0.43\ud ,\ud \ud γ\ud E\ud 1\ud M\ud 2\ud =\ud −\ud 0.85\ud ±\ud 0.72\ud , and \ud γ\ud M\ud 1\ud E\ud 2\ud =\ud 2.04\ud ±\ud 0.43\ud , in units of \ud 10\ud −\ud 4\ud fm\ud 4\ud .

Published
2020
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23. Influence of electron cooling on the polarization lifetime of a horizontally polarized storage ring beam

Author

Andreas Lehrach, G. Guidoboni, P. Lenisa, D. Prasuhn, V. Shmakova, I. Keshelashvili, Ralf Gebel, B. Lorentz, H. Ströher, A. Nass, Frank Rathmann, A.K. Kacharava, E. J. Stephenson, A. Pesce, D. Mchedlishvili, Yu. Valdau, J. Pretz, Richard Talman, Aleksandra Wrońska, A. Saleev, S. Dymov, Y. Senichev, C. Weidemann, S. Karanth, Nikolai N. Nikolaev, V. Hejny, G. Ciullo, and P. Wüstner

Subjects
Accelerator Physics (physics.acc-ph), Nuclear and High Energy Physics, Field (physics), Electron cooling, Socio-culturale, FOS: Physical sciences, Spin coherence time, 01 natural sciences, law.invention, PE2_2, Optics, PE2_1, law, Polarization, 0103 physical sciences, ddc:530, Polarization, Spin coherence time, Electron cooling, 010306 general physics, PE2_3, Instrumentation, Spin-½, Physics, 010308 nuclear & particles physics, business.industry, Polarization (waves), Deuterium, Physics::Accelerator Physics, Physics - Accelerator Physics, business, Intensity (heat transfer), Beam (structure), Storage ring
Abstract

A previous publication has shown that the in-plane polarization (IPP) component of a polarized 0.97-GeV/c deuteron beam in the COSY storage ring may acquire a polarization half-life in excess of 1000 s through a combination of beam bunching, electron cooling (prior to any spin manipulation), sextupole field adjustment, and a limitation of the beam intensity. This paper documents further tests pointing to additional gains in the IPP lifetime if cooling is active throughout the beam store., 11 pages, 6 figures Submitted to Physical Review Accelerators and Beams

Published
2020
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24. Observation of the p η ′ Cusp in the New Precise Beam Asymmetry Σ Data for γ p → p η

Author

F, Afzal, Y, Wunderlich, A V, Anisovich, D, Bayadilov, R, Beck, M, Becker, E, Blanke, K-Th, Brinkmann, S, Ciupka, V, Crede, M, Dieterle, H, Dutz, D, Elsner, S, Friedrich, F, Frommberger, A, Gridnev, M, Gottschall, M, Grüner, E, Gutz, C, Hammann, J, Hannappel, J, Hartmann, W, Hillert, J, Hoff, P, Hoffmeister, C, Honisch, T, Jude, H, Kalinowsky, F, Kalischewski, I, Keshelashvili, P, Klassen, F, Klein, E, Klempt, K, Koop, P, Kroenert, B, Krusche, M, Lang, I, Lopatin, P, Mahlberg, U-G, Meißner, F, Messi, V, Metag, W, Meyer, B, Mitlasóczki, J, Müller, J, Müllers, M, Nanova, K, Nikonov, V, Nikonov, V, Novinskiy, R, Novotny, D, Piontek, G, Reicherz, L, Richter, D, Rönchen, T, Rostomyan, B, Salisbury, A, Sarantsev, D, Schaab, C, Schmidt, H, Schmieden, J, Schultes, T, Seifen, V, Sokhoyan, C, Sowa, K, Spieker, N, Stausberg, A, Thiel, U, Thoma, T, Triffterer, M, Urban, G, Urff, H, van Pee, D, Walther, Ch, Wendel, U, Wiedner, A, Wilson, A, Winnebeck, and L, Witthauer

Subjects
Nuclear Theory, Physics::Accelerator Physics, ddc:530, Nuclear Experiment
Abstract

Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W=1748 MeV to W=2045 MeV). The data cover the full solid angle that allows for a precise moment analysis. For the first time, a strong cusp effect in a polarization observable has been observed that is an effect of a branch-point singularity at the pη^{'} threshold [E_{γ}=1447 MeV (W=1896 MeV)]. The latest BnGa partial wave analysis includes the new beam asymmetry data and yields a strong indication for the N(1895)1/2^{-} nucleon resonance, demonstrating the importance of including all singularities for a correct determination of partial waves and resonance parameters.

Published
2020
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25. Development of a multi-channel power supply for silicon photo-multipliers used with inorganic scintillators

Author

Z. Metreveli, T. Hahnraths, F. Müller, A.K. Kacharava, H. Ströher, O. Javakhishvili, I. Keshelashvili, D. Shergelashvili, Helmut Soltner, T. Sefzick, D. Mchedlishvili, and M. Gagoshidze

Subjects
Nuclear and High Energy Physics, Physics - Instrumentation and Detectors, Physics::Instrumentation and Detectors, FOS: Physical sciences, Scintillator, 01 natural sciences, Lyso, 030218 nuclear medicine & medical imaging, law.invention, 03 medical and health sciences, 0302 clinical medicine, Silicon photomultiplier, law, 0103 physical sciences, ddc:530, Nuclear Experiment (nucl-ex), Instrumentation, Nuclear Experiment, Physics, Calorimeter (particle physics), 010308 nuclear & particles physics, business.industry, Electrical engineering, Polarimeter, Instrumentation and Detectors (physics.ins-det), Modular design, business, Remote control, Voltage
Abstract

The motivation of the current R&D project is based upon the requirements of the JEDI international collaboration 1 aiming to measure Electric Dipole Moments (EDMs) of charged particles in storage rings. One of the most important elements of such an experiment will be a specially designed polarimeter with the detection system based on a modular inorganic scintillator (LYSO crystal) calorimeter. The calorimeter modules are read out by Silicon Photo Multipliers (SiPMs). This paper describes the development of a multi-channel power supply for the polarimeter modules, providing very stable and clean bias voltages for SiPMs. In order to ensure the best possible performance of SiPMs in conjunction with the crystal-based calorimeter modules and to guarantee the required level of calorimeter stability, several quality requirements have to be met by the power supply. Additionally, it is required to provide features including remote control via the network, ramping of the output voltage, measuring and sending the information about its output voltages and currents, etc. The obtained results demonstrate that the goals for the JEDI polarimeter are met. The developed hardware will be useful in other fields of fundamental and applied research, medical diagnostic techniques and industry, where SiPMs are used.

Published
2020
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26. A new beam polarimeter at COSY to search for electric dipole moments of charged particles

Author

F. Müller, O. Javakhishvili, D. Shergelashvili, I. Keshelashvili, D. Mchedlishvili, F. Abusaif, A. Aggarwal, L. Barion, S. Basile, J. Böker, N. Canale, G. Ciullo, S. Dymov, O. Felden, M. Gagoshidze, R. Gebel, N. Demary, K. Grigoryev, D. Grzonka, T. Hahnrath, V. Hejny, A. Kacharava, V. Kamerdzhiev, S. Karanth, A. Kulikov, A. Lehrach, P. Lenisa, N. Lomidze, B. Lorentz, G. Macharashvili, A. Magiera

Published
2020
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27. Deuteron analysing powers in deuteron–proton elastic scattering at 1.2 and 2.27 GeV

Author

K. Grigoryev, A. Khoukaz, B. Lorentz, M. Hartmann, Andreas Lehrach, Colin Wilkin, M. Papenbrock, Ralf Engels, S. Barsov, M. D. Tabidze, S. Merzliakov, N.L. Lomidze, V.I. Komarov, Z. Bagdasarian, S. Dymov, Yu. N. Uzikov, M. S. Nioradze, H. Ströher, I. Keshelashvili, P. Kulessa, D. Prasuhn, Johann Haidenbauer, V. Serdyuk, Yu. Valdau, V. Shmakova, Ralf Gebel, D. Mchedlishvili, S. Mikirtychyants, H. Ohm, Frank Rathmann, A.K. Kacharava, A. I. Kulikov, G.G. Macharashvili, and D. Tsirkov

Subjects
Physics, Elastic scattering, Nuclear and High Energy Physics, Nuclear Theory, Proton, 010308 nuclear & particles physics, Scattering, FOS: Physical sciences, Kinetic energy, 01 natural sciences, Nuclear Theory (nucl-th), Nuclear physics, Deuterium, 0103 physical sciences, ddc:530, Tensor, Nuclear Experiment (nucl-ex), Nuclear Experiment, 010306 general physics, Glauber, Storage ring
Abstract

The vector and tensor analysing powers in deuteron-proton elastic scattering have been measured in the forward hemisphere at deuteron kinetic energies of 1.2 GeV and 2.27 GeV using the ANKE spectrometer at the COSY storage ring. The results are compared with other experimental data and with predictions made within the framework of Glauber multiple scattering theory., Comment: 11 pages with 8 figures. To be submitted for publication

Published
2018
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28. Measurement of the helicity asymmetry

Author

M, Gottschall, F, Afzal, A V, Anisovich, D, Bayadilov, R, Beck, M, Bichow, K Th, Brinkmann, V, Crede, M, Dieterle, F, Dietz, H, Dutz, H, Eberhardt, D, Elsner, R, Ewald, K, Fornet-Ponse, St, Friedrich, F, Frommberger, A, Gridnev, M, Grüner, E, Gutz, Ch, Hammann, J, Hannappel, J, Hartmann, W, Hillert, Ph, Hoffmeister, Ch, Honisch, T, Jude, S, Kammer, H, Kalinowsky, I, Keshelashvili, P, Klassen, F, Klein, E, Klempt, K, Koop, B, Krusche, M, Kube, M, Lang, I, Lopatin, P, Mahlberg, K, Makonyi, V, Metag, W, Meyer, J, Müller, J, Müllers, M, Nanova, V, Nikonov, R, Novotny, D, Piontek, G, Reicherz, T, Rostomyan, A, Sarantsev, Ch, Schmidt, H, Schmieden, T, Seifen, V, Sokhoyan, K, Spieker, A, Thiel, U, Thoma, M, Urban, H van, Pee, D, Walther, Ch, Wendel, D, Werthmüller, U, Wiedner, A, Wilson, A, Winnebeck, L, Witthauer, and Y, Wunderlich

Subjects
Regular Article – Experimental Physics
Abstract

A measurement of the double-polarization observable E for the reaction \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma p\rightarrow \pi ^0 p$$\end{document}γp→π0p is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_4$$\end{document}4H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_9$$\end{document}9OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_\gamma =600$$\end{document}Eγ=600 to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.

Published
2019

29. A new approach: LYSO based polarimetry for the EDM measurements

Author

F. Müller, D. Mchedlishvili, D. Shergelashvili, and I. Keshelashvili

Subjects
Physics, History, 010308 nuclear & particles physics, business.industry, Polarimetry, 01 natural sciences, Lyso, Computer Science Applications, Education, Optics, 0103 physical sciences, ddc:530, 010306 general physics, business
Abstract

18th International Conference on Calorimetry in Particle Physics, CALOR2018, Eugene, Oregon, USA, 21 May 2018 - 25 May 2018; Journal of physics / Conference series 1162(1), 012029 (2019). doi:10.1088/1742-6596/1162/1/012029 special issue: "18th International Conference on Calorimetry in Particle Physics (CALOR2018) 21–25 May 2018, Eugene, Oregon, USA", Published by IOP Publ., Bristol

Published
2019
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30. Low-energy spin-physics experiments with polarized beams and targets at the COSY storage ring

Author

Paolo Lenisa, Ralf Engels, B. Lorentz, S. Barsov, S. Martin, M. Statera, Helmut Soltner, S. Merzliakov, L. Semke, Frank Rathmann, A. Kulikov, G. Ciullo, S. Bertelli, C. Weidemann, G.G. Macharashvili, D. Prasuhn, N.L. Lomidze, S. Dymov, G. Tagliente, Yu. N. Uzikov, M. D. Tabidze, Thomas Krings, K. Grigoryev, A.K. Kacharava, A. Pesce, A. Nass, Johann Haidenbauer, A. Cotta Ramusino, Yu. Valdau, D. Eversheim, Ralf Gebel, H. Jagdfeld, P. Wüstner, P. Zupranski, L. Barion, V. Carassiti, Roberto Malaguti, S. Squerzanti, A. Kononov, P. Thörngren-Engblom, Nikolai N. Nikolaev, S. Mikirtychiants, V. Hejny, S.V. Trusov, H. Ströher, I. Keshelashvili, Andreas Lehrach, M. Contalbrigo, and E. Steffens

Subjects
Polarized beams, Polarized beams, Particle accelerators, Storage rings, Beam handling, Solid-state detectors, Polarimetry, Socio-culturale, Accelerator Physics and Instrumentation, 01 natural sciences, Particle detector, 010305 fluids & plasmas, law.invention, Nuclear physics, Storage rings, Resonator, PE2_2, law, 0103 physical sciences, Solid-state detectors, lcsh:QC350-467, Beam handling, 010306 general physics, Nuclear Experiment, Instrumentation, PE2_3, lcsh:QC120-168.85, Physics, Particle accelerator, Acceleratorfysik och instrumentering, lcsh:QC1-999, Particle accelerators, Semiconductor detector, ddc:540, Measuring instrument, lcsh:Descriptive and experimental mechanics, Realization (systems), lcsh:Physics, lcsh:Optics. Light, Storage ring
Abstract

A low-energy spin-physics program is being developed at the COSY storage ring. To support the planned experimental activities, several experimental tools for polarized beams and targets have been developed. The paper presents the physics case and the readiness of the setup for its realization. QC 20190905. QC 20191203Although the hadron physics program has been officially terminated, various experimental activities are underway at the COSY storage ring of Forschungszentrum Jülich. Besides the feasibility studies related to the search for electric dipole moments [2], low-energy spin-physics experiments employing polarized beam and targets appear as an additional focus. This paper is devoted to these studies.

Published
2019
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31. A storage ring EDM polarimeter

Author

I. Keshelashvili, D. Mchedlishvili, and O. Javakhishvili

Subjects
Physics, History, Optics, Physics::Instrumentation and Detectors, business.industry, Polarimeter, business, Storage ring, Computer Science Applications, Education
Abstract

The search for electric dipole moments (EDM) of elementary particles is one of the hot topic in contemporary particle physics. The method to measure charged particle EDMs (p,d) is to observe the time development of a polarized beam in a dedicated storage ring (srEDM). This requires a new polarimeter with a special target system which is under development at COSY-Juelich. The particle detector consists of the two layers: a plastic scintillator for ?E and an inorganic LYSO crystal as a calorimeter. Both systems are readout by multi-pixel SiPM (silicon photo multiplier) arrays. SiPMs operate at significantly lower supply voltages compared to the traditional multi-stage vacuum tubes, simplifying detector construction and operation. The developed calorimeter modules operate at voltages up to 30 Volt. For this purpose a modular, high precision voltage supply has been developed together with slow control and voltage monitoring systems. The fully assembled calorimeter part of the polarimeter has been successfully tested together with its high speed and high-resolution sampling ADC-based readout. All test have been carried out using solid block target. However, the final polarimeter will include a ballistic target system which will be shooting point-like diamond pellet through the beam. The movement of the pellet will be precisely tracked in three dimensions and synchronized with the data acquisition system. This will allow us to reconstruct the polarization profile of the beam. Currently, the mechanical and electrical systems for the pellet target are under development. Recent achievements and experimental results of this project are summarized and discussed in this paper.

Published
2020
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32. New data on γ→p→→ηp with polarized photons and protons and their implications for N⁎ → Nη decays

Author

P. Klassen, V. Hannen, J. Herick, Reinhard Beck, Ch. Wendel, S. Kammer, Jens Hartmann, V. Metag, H. van Pee, F. Dietz, P. Mahlberg, Ch. Honisch, Ch. Schmidt, Th. Challand, S. Böse, T. C. Jude, H. Kalinowsky, M. Bichow, K. Koop, T. Rostomyan, M. Becker, I. Jaegle, G. Reicherz, A. Berlin, A. Käser, Friedrich Klein, M. Gottschall, D. Kaiser, A. Wilson, R. Schmitz, T. Seifen, R. Ewald, C. Rosenbaum, Yasser Maghrbi, F. Afzal, H. Dutz, O. Jahn, H. Eberhardt, D. Elsner, A. Thiel, R. W. Novotny, Ph. Hoffmeister, V. Crede, S. Goertz, A. V. Anisovich, J. Müller, H. Schmieden, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, M. Grüner, B. Roth, Frank Frommberger, Matthew Lang, S. Friedrich, K. Makonyi, Francesco Messi, B. Bantes, J. Hannappel, Wolfgang Hillert, M. Kube, E. Gutz, Ulrich Wiedner, M. Urban, V. Kleber, U. Thoma, V. Sokhoyan, F. Kalischewski, I. Keshelashvili, W. Meyer, J. Müllers, Eberhard Klempt, K. Fornet-Ponse, C. Funke, D. V. Novinski, Lilian Witthauer, Ch. Hammann, B. Krusche, P. Drexler, A. Winnebeck, V. A. Nikonov, M. Dieterle, K.-T. Brinkmann, Yu. A. Beloglazov, A. V. Sarantsev, D. Piontek, I. V. Lopatin, and D. Walther

Subjects
Physics, Nuclear physics, Nuclear and High Energy Physics, Photon, Meson, 010308 nuclear & particles physics, 0103 physical sciences, Polarization observables, Solid angle, 010306 general physics, Branching (polymer chemistry), Nucleon, 01 natural sciences
Abstract

The polarization observables T , E , P , H , and G in photoproduction of η mesons off protons are measured for photon energies from threshold to W = 2400 MeV (T), 2280 MeV (E), 1620 MeV ( P , H ), or 1820 MeV (G), covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, JuBo, and BnGa partial-wave analyses. A refit within the BnGa approach including further data yields precise branching ratios for the Nη decay of nucleon resonances. A Nη-branching ratio of 0.33 ± 0.04 for N ( 1650 ) 1 / 2 − is found, which reduces the large and controversially discussed Nη-branching ratio difference of the two lowest mass J P = 1 / 2 − -resonances significantly.

Published
2020
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33. Measurement of the beam-helicity asymmetry in photoproduction of π0η pairs on carbon, aluminum, and lead

Author

R. A. Miskimen, A. G. Denig, Durga Paudyal, M. Wolfes, I. Keshelashvili, Yu. A. Usov, O. Steffen, K. Spieker, P. Pedroni, Susanna Costanza, P. Aguar-Bartolomé, Concettina Sfienti, A. N. Mushkarenkov, M. Ostrick, D. G. Middleton, M. Günther, S. Garni, A. Powell, I. Supek, A. Käser, R. Beck, I. Gorodnov, M. Unverzagt, V. L. Kashevarov, F. Cividini, Roderick M. Macrae, L. V. Fil'kov, P. Adlarson, M. Oberle, S. Abt, E. J. Downie, Patrick Achenbach, D. P. Watts, S. Cherepnya, A. J. Sarty, K. Bantawa, G. M. Huber, Z. Ahmed, S. Kay, I. I. Strakovsky, T. Rostomyan, K. Livingston, S. Lutterer, B. Strandberg, S. Gardner, N. S. Borisov, C. Mullen, Guy Ron, D. I. Glazier, S. Wagner, H. J. Arends, W. J. Briscoe, A. B. Lazarev, Michaela Thiel, A. Neiser, A. Fix, A. Braghieri, Th. Strub, P. Drexler, F. Afzal, A. B. Neganov, Nicholas Zachariou, W. Gradl, J. Wettig, J. C. McGeorge, V. Sokhoyan, P. P. Martel, J. R. M. Annand, D. Hornidge, E. Mornacchi, I. J. D. MacGregor, M. Korolija, David Manley, N. K. Walford, B. Krusche, K. Altangerel, E. Rickert, M. Biroth, P. B. Otte, R. Kondratiev, G. M. Gurevich, S. N. Prakhov, Lilian Witthauer, M. Dieterle, Lena Heijkenskjöld, M. I. Ferretti Bondy, Andy Thomas, A. Thiel, D. Werthmüller, C. Collicott, and M. Bashkanov

Subjects
Nuclear and High Energy Physics, Proton, media_common.quotation_subject, Nuclear Theory, chemistry.chemical_element, 7. Clean energy, 01 natural sciences, Asymmetry, Nuclear physics, Aluminium, 0103 physical sciences, Intermediate state, Nuclear Experiment, 010306 general physics, QC, media_common, Physics, 010308 nuclear & particles physics, Helicity, lcsh:QC1-999, 3. Good health, chemistry, High Energy Physics::Experiment, Nucleon, Carbon, lcsh:Physics, Beam (structure)
Abstract

The beam-helicity asymmetry was measured, for the first time, in photoproduction of $\pi^{0}\eta$ pairs on carbon, aluminum, and lead, with the A2 experimental setup at MAMI. The results are compared to an earlier measurement on a free proton and to the corresponding theoretical calculations. The Mainz model is used to predict the beam-helicity asymmetry for the nuclear targets. The present results indicate that the photoproduction mechanism for $\pi^{0}\eta$ pairs on nuclei is similar to photoproduction on a free nucleon. This process is dominated by the $D_{33}$ partial wave with the $\eta\Delta(1232)$ intermediate state., Comment: Accepted for publication in Physics Letters B (2020)

Published
2020
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34. The $\eta^{\prime}$ η -carbon potential at low meson momenta

Author

D. Elsner, K. Koop, Frank Frommberger, V. Metag, Ph. Hoffmeister, J. Müller, B. Krusche, E. Gutz, D. Kaiser, K.-T. Brinkmann, T. Triffterer, C. Sowa, J. Müllers, A. Wilson, S. Friedrich, T. Seifen, Matthew Lang, J. Hannappel, B. Bantes, Francesco Messi, Ulrich Wiedner, E. Ya. Paryev, U. Thoma, D. Walther, Jens Hartmann, F. Afzal, Ch. Hammann, Reinhard Beck, P. Drexler, V. Crede, Ch. Honisch, Y. Wunderlich, D. Piontek, Ch. Schmidt, Hans-Georg Zaunick, H. Eberhardt, T. C. Jude, M. Becker, Ch. Funke, Ch. Wendel, D. Werthmüller, Wolfgang Hillert, M. Grüner, I. Keshelashvili, T. Rostomyan, Lilian Witthauer, M. Gottschall, S. Böse, K. Makonyi, M. Urban, V. Sokhoyan, H. van Pee, Friedrich Klein, K. Spieker, D. Schaab, R. Schmitz, A. Thiel, F. Kalischewski, H. Schmieden, D. E. Bayadilov, and Mariana Nanova

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Meson, 010308 nuclear & particles physics, Hadron, Carbon-12, Elementary particle, 01 natural sciences, Baryon, 0103 physical sciences, High Energy Physics::Experiment, Production (computer science), Nuclear Experiment, 010306 general physics, Nucleon, Boson
Abstract

The production of $\eta^{\prime}$ mesons in coincidence with forward-going protons has been studied in photon-induced reactions on 12C and on a liquid hydrogen (LH2) target for incoming photon energies of 1.3-2.6 GeV at the electron accelerator ELSA. The $\eta^{\prime}$ mesons have been identified via the $\eta^{\prime} \rightarrow \pi^{0} \pi^{0}\eta \rightarrow 6 \gamma$ decay registered with the CBELSA/TAPS detector system. Coincident protons have been identified in the MiniTAPS BaF2 array at polar angles of $2^{\circ} \le \theta_{p} \le 11^{\circ}$ . Under these kinematic constraints the $\eta^{\prime}$ mesons are produced with relatively low kinetic energy ( $\approx 150$ MeV) since the coincident protons take over most of the momentum of the incident-photon beam. For the C-target this allows the determination of the real part of the $\eta^{\prime}$ -carbon potential at low meson momenta by comparing with collision model calculations of the $\eta^{\prime}$ kinetic energy distribution and excitation function. Fitting the latter data for $\eta^{\prime}$ mesons going backwards in the center-of-mass system yields a potential depth of $V = -(44 \pm 16(stat) \pm 15(syst))$ MeV, consistent with earlier determinations of the potential depth in inclusive measurements for average $\eta^{\prime}$ momenta of $\approx 1.1$ GeV/c. Within the experimental uncertainties, there is no indication of a momentum dependence of the $\eta^{\prime}$ -carbon potential. The LH2 data, taken as a reference to check the data analysis and the model calculations, provide differential and integral cross sections in good agreement with previous results for $\eta^{\prime}$ photoproduction off the free proton.

Published
2018
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35. Measurement of the decay η′→π0π0η at MAMI

Author

Z. Ahmed, David Manley, K. Livingston, S. Gardner, David Hamilton, N. S. Borisov, I. Supek, I. Keshelashvili, H. J. Arends, Ron L. Workman, T. Rostomyan, A. G. Denig, Michaela Thiel, Durga Paudyal, J. C. McGeorge, S. Wagner, M. Ostrick, M. Wolfes, A. B. Lazarev, Lorenzo Zana, B. Oussena, C. Collicott, K. Spieker, A. B. Neganov, M. Korolija, P. P. Martel, D. P. Watts, A. Braghieri, Th. Strub, P. Ott, J. R. M. Annand, R. Kondratiev, D. G. Middleton, C. S. Akondi, G. M. Gurevich, D. Hornidge, S. Kay, C. Sfienti, A. J. Sarty, I. J. D. MacGregor, A. Käser, V. L. Kashevarov, B. Krusche, A. Neiser, W. Gradl, Lilian Witthauer, Yu. A. Usov, O. Steffen, S. N. Prakhov, R. Miskimen, Andy Thomas, A. Thiel, P. Pedroni, A. Polonski, Igor Strakovsky, Susanna Costanza, J. Linturi, Reinhard Beck, M. Dieterle, M. I. Ferretti Bondy, D. Glowa, Guy Ron, S. Garni, L. Tiator, W. J. Briscoe, P. B. Otte, D. I. Glazier, J. Wettig, V. Sokhoyan, F. Afzal, G. M. Huber, M. Oberle, M. Unverzagt, A. Rajabi, F. Cividini, P. Adlarson, A. N. Mushkarenkov, E. J. Downie, and D. Werthmüller

Subjects
Cusp (singularity), Physics, Meson, 010308 nuclear & particles physics, Resolution (electron density), Magnitude (mathematics), Scattering length, 01 natural sciences, Nuclear physics, 0103 physical sciences, 010306 general physics, Microtron, Parametrization, Sign (mathematics)
Abstract

An experimental study of the η′→π0π0η→6γ decay has been conducted with the best up-to-date statistical accuracy, by measuring η′ mesons produced in the γp→η′p reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The results obtained for the standard parametrization of the η′→π0π0η matrix element are consistent with the most recent results for η′→ππη decays, but have smaller uncertainties. The available statistics and experimental resolution allowed, for the first time, an observation of a structure below the π+π- mass threshold, the magnitude and sign of which, checked within the framework of the nonrelativistic effective-field theory, demonstrated good agreement with the cusp that was predicted based on the ππ scattering length combination, a0-a2, extracted from K→3π decays.

Published
2018
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36. High-statistics measurement of the η→3π0 decay at the Mainz Microtron

Author

D. Paudyal, E. Mornacchi, V. L. Kashevarov, Lena Heijkenskjöld, I. J. D. MacGregor, J. Ahrens, Igor Strakovsky, R. Kondratiev, R. Miskimen, C. B. Hamill, M. Oberle, M. Biroth, F. Afzal, A. Käser, A. Lazarev, D. I. Glazier, G. M. Gurevich, I. Supek, C. Sfienti, F. Cividini, M. Bashkanov, P. Drexler, M. Dieterle, L. Zana, I. Gorodnov, A. Mushkarenkov, M. I. Ferretti Bondy, N. K. Walford, A. Thiel, Patrick Achenbach, S. Cherepnya, Yu. A. Usov, O. Steffen, I. Keshelashvili, E. J. Downie, S. Kay, Reinhard Beck, A. Braghieri, D. Hornidge, J. R. M. Annand, P. Aguar-Bartolomé, David Manley, V. Lisin, A. Fix, A. Denig, A. Polonski, P. Pedroni, M. Wolfes, A. B. Neganov, D. Werthmüller, S. Costanza, A. Neiser, M. Unverzagt, S. Abt, S. Wagner, Th. Strub, D. G. Middleton, W. J. Briscoe, S. N. Prakhov, Z. Ahmed, G. Ron, A. Thomas, G. M. Huber, P. Adlarson, Lilian Witthauer, A. J. Sarty, P. B. Otte, C. Collicott, D. P. Watts, J. C. McGeorge, K. Bantawa, P. P. Martel, M. Korolija, B. Krusche, K. Livingston, S. Lutterer, V. Sokhoyan, B. Strandberg, S. Gardner, N. S. Borisov, T. Rostomyan, H. J. Arends, L. V. Fil'kov, W. Gradl, J. Wettig, M. Thiel, M. Ostrick, S. Garni, and K. Spieker

Subjects
Cusp (singularity), Physics, Meson, 010308 nuclear & particles physics, Dalitz plot, 01 natural sciences, 7. Clean energy, Moment (mathematics), Nonlinear system, Quadratic equation, 0103 physical sciences, Statistics, High Energy Physics::Experiment, Nuclear Experiment, 010306 general physics, Microtron, Parametrization
Abstract

The largest, at the moment, statistics of 7×106η→3π0 decays, based on 6.2×107η mesons produced in the γp→ηp reaction, has been accumulated by the A2 Collaboration at the Mainz Microtron, MAMI. It allowed a detailed study of the η→3π0 dynamics beyond its conventional parametrization with just the quadratic slope parameter α and enabled, for the first time, a measurement of the second-order term and a better understanding of the cusp structure in the neutral decay. The present data are also compared to recent theoretical calculations that predict a nonlinear dependence along the quadratic distance from the Dalitz-plot center.

Published
2018
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37. Experimental study of the γp→π0ηp reaction with the A2 setup at the Mainz Microtron

Author

C. B. Hamill, K. Livingston, S. Lutterer, S. Garni, W. Gradl, B. Strandberg, S. Gardner, N. S. Borisov, N. K. Walford, D. Paudyal, A. Polonski, C. Sfienti, B. Krusche, E. J. Downie, A. Lazarev, K. Spieker, S. Wagner, M. Günther, M. Biroth, P. Pedroni, M. Bashkanov, D. Werthmüller, S. Abt, M. Dieterle, M. Ostrick, M. Oberle, C. Collicott, D. P. Watts, L. Zana, M. I. Ferretti Bondy, J. Wettig, Yu. A. Usov, M. Unverzagt, O. Steffen, A. Thomas, R. Kondratiev, K. Bantawa, Z. Ahmed, F. Cividini, David Manley, A. Fix, A. J. Sarty, V. L. Kashevarov, Lena Heijkenskjöld, G. M. Huber, P. Adlarson, S. Kay, M. Thiel, P. Aguar-Bartolomé, I. Gorodnov, S. N. Prakhov, P. Drexler, A. Braghieri, D. Hornidge, G. Ron, V. Sokhoyan, V. Lisin, F. Afzal, T. Rostomyan, Th. Strub, H. J. Arends, Reinhard Beck, D. G. Middleton, E. Mornacchi, Lilian Witthauer, J. Ahrens, Patrick Achenbach, R. Miskimen, Igor Strakovsky, L. V. Fil'kov, W. J. Briscoe, I. J. D. MacGregor, I. Supek, A. B. Neganov, G. M. Gurevich, J. R. M. Annand, D. I. Glazier, A. Thiel, A. Denig, A. Mushkarenkov, S. Costanza, A. Neiser, J. C. McGeorge, M. Wolfes, P. B. Otte, A. Käser, P. P. Martel, M. Korolija, I. Keshelashvili, and S. Cherepnya

Subjects
Physics, Particle physics, Basis (linear algebra), 010308 nuclear & particles physics, Observable, 7. Clean energy, 01 natural sciences, Reaction dynamics, 0103 physical sciences, Photon polarization, Range (statistics), Photon beam, Nuclear Experiment, 010306 general physics, Microtron, Energy (signal processing)
Abstract

The data available from the A2 Collaboration at MAMI were analyzed to select the γp→π0ηp reaction on an event-by-event basis, which allows for partial-wave analyses of three-body final states to obtain more reliable results, compared to fits to measured distributions. These data provide the world's best statistical accuracy in the energy range from threshold to Eγ=1.45 GeV, allowing a finer energy binning in the measurement of all observables needed for understanding the reaction dynamics. The results obtained for the measured observables are compared to existing models, and the impact from the new data is checked by the fit with the revised Mainz model.

Published
2018
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38. First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons

Author

J. Wettig, A. Käser, M. Bashkanov, S. Costanza, M. Dieterle, R. Miskimen, S. Wagner, M. Thiel, G. Reicherz, P. Adlarson, F. Cividini, Yu. A. Usov, O. Steffen, R. Kondratiev, H. J. Arends, B. Krusche, V. L. Kashevarov, Lena Heijkenskjöld, P. P. Martel, M. Korolija, M. Unverzagt, E. Mornacchi, I. Supek, F. Afzal, A. Lazarev, S. Abt, C. Collicott, D. P. Watts, G. M. Huber, M. Ostrick, I. J. D. MacGregor, S. N. Prakhov, G. Ron, J. Ahrens, G. M. Gurevich, A. B. Neganov, A. Thiel, M. Günther, P. B. Otte, D. Paudyal, L. Zana, N. K. Walford, W. Gradl, E. J. Downie, Lilian Witthauer, K. Livingston, S. Lutterer, M. Biroth, W. Meyer, C. Sfienti, A. Braghieri, V. Sokhoyan, N. S. Borisov, D. Hornidge, Igor Strakovsky, V. Lisin, T. Rostomyan, A. J. Sarty, D. Werthmüller, Reinhard Beck, David Manley, A. Fix, Th. Strub, S. Kay, D. I. Glazier, A. Mushkarenkov, A. Polonski, A. Thomas, I. Gorodnov, W. J. Briscoe, M. Wolfes, M. Oberle, P. Drexler, P. Pedroni, Volker Metag, Z. Ahmed, Patrick Achenbach, J. R. M. Annand, A. Denig, A. Neiser, S. Garni, K. Spieker, and I. Keshelashvili

Subjects
Nuclear and High Energy Physics, Photon, Nuclear Theory, FOS: Physical sciences, 7. Clean energy, 01 natural sciences, Nuclear physics, Pion, 0103 physical sciences, Neutron, ddc:530, Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment, Spin-½, Physics, 010308 nuclear & particles physics, Helicity, lcsh:QC1-999, 3. Good health, Deuterium, Nucleon, lcsh:Physics, Crystal Ball, reaction gamma-p, polarization, eta, mesons, mami, Pi(0)-pairs, photon, proton, pairs
Abstract

The helicity-dependent cross sections for the photoproduction of $\pi^0\eta$ pairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball - TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the $\sigma_{1/2}$ (photon and target spin antiparallel) and $\sigma_{3/2}$ (parallel spins) components to be measured for quasi-free production of $\pi^0\eta$ pairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant protons and neutrons. The absolute couplings for protons and neutrons are also identical. This means that nucleon resonances contributing to this reaction in the investigated energy range have almost equal electromagnetic helicity couplings, $A_{1/2}^{n,p}$ and $A_{3/2}^{n,p}$. Identical couplings for protons and neutrons are typical for $\Delta$ resonances and identical $A_{1/2}$ and $A_{3/2}$ components are only possible for $J\geq 3/2$ states, which constrains possible contributions of nucleon resonances., Comment: accepted for publication in Phys. Lett. B

Published
2018
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39. Phase measurement for driven spin oscillations in a storage ring

Author

S. Mey, P. Zupranski, L. Barion, M. S. Nioradze, A. Saleev, Martin Berz, D. Mchedlishvili, G. Guidoboni, E. J. Stephenson, Aleksandra Wrońska, R. Talman, Yu. N. Uzikov, H. Stockhorst, C. Weidemann, P. Wuestner, J. Slim, Dirk Heberling, D. Eversmann, P. Maanen, V. Schmidt, A. Stahl, B. Lorentz, W. Augustyniak, J. Pretz, K. Grigoryev, M. Bai, N.L. Lomidze, J. Hetzel, Alexander J. Silenko, H. Stroeher, Yu. Valdau, Nikolai N. Nikolaev, S. Dymov, D. Prasuhn, V. Hejny, Y. Semertzidis, E. Valetov, F. Mueller, Paolo Lenisa, H. Soltner, V. Shmakova, S. Chekmenev, A. Magiera, Rolf Stassen, F. Hinder, G.G. Macharashvili, G. Ciullo, G. Tagliente, A. Vassiliev, D. Grzonka, Ivan Koop, M. Gaisser, A.K. Kacharava, N. Hempelmann, Andreas Lehrach, A. Kulikov, I. Keshelashvili, M. D. Tabidze, Martin Rosenthal, Maria Zurek, F. Trinkel, Pia Thörngren Engblom, V. Kamerdzhiev, Y. Senichev, A. Nass, Frank Rathmann, Z. Bagdasarian, A. Pesce, Ralf Gebel, and Publica

Subjects
Physics, Physics and Astronomy (miscellaneous), Nuclear and High Energy Physics, Surfaces and Interfaces, Accelerator Physics (physics.acc-ph), 010308 nuclear & particles physics, Socio-culturale, FOS: Physical sciences, Polarization (waves), 01 natural sciences, 13.40.Em, 11.30.Er, 29.20.D, 29.20.dg, 29.20.db, Physical Sciences, 0103 physical sciences, lcsh:QC770-798, Fysik, lcsh:Nuclear and particle physics. Atomic energy. Radioactivity, Physics - Accelerator Physics, ddc:530, Radio frequency, Atomic physics, 010306 general physics, Storage ring
Abstract

Physical review accelerators and beams 21(4), 042002 (2018). doi:10.1103/PhysRevAccelBeams.21.042002, Published by American Physical Society, College Park, MD

Published
2018
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40. Photoproduction of π 0 mesons off protons and neutrons in the second and third nucleon resonance regions

Author

S. Kay, D. Gurevich, V. Metag, M. Wolfes, M. Bashkanov, H. J. Arends, Igor Strakovsky, S. N. Prakhov, G. Ron, B. Krusche, Lilian Witthauer, A. B. Neganov, M. Dieterle, M. Günther, R. Kondratiev, L. V. Fil'kov, S. Cherepnya, J. Ahrens, R. Miskimen, Yu. A. Usov, V. Sokhoyan, O. Steffen, F. Afzal, S. Wagner, I. Gorodnov, M. Oberle, D. I. Glazier, P. Drexler, F. Cividini, T. Rostomyan, M. Ostrick, M. Unverzagt, C. Sfienti, A. Thiel, G. M. Huber, K. Livingston, S. Lutterer, David Manley, A. Mushkarenkov, A. Lazarev, N. S. Borisov, A. Braghieri, D. Hornidge, J. R. M. Annand, V. Lisin, K. Spieker, J. C. McGeorge, N. K. Walford, A. Denig, S. Costanza, A. Neiser, D. Paudyal, A. Polonski, I. Keshelashvili, S. Abt, Th. Strub, I. Supek, D. G. Middleton, A. Thomas, A. J. Sarty, V. L. Kashevarov, Lena Heijkenskjöld, S. Garni, B. Oussena, P. Pedroni, L. Zana, C. Collicott, D. P. Watts, Z. Ahmed, E. J. Downie, D. Werthmüller, Reinhard Beck, W. J. Briscoe, P. P. Martel, M. Korolija, A. Käser, P. B. Otte, W. Gradl, P. Aguar Bartolomé, J. Wettig, M. Thiel, M. Biroth, E. Mornacchi, and I. J. D. MacGregor

Subjects
Physics, Nuclear reaction, Proton, Meson, 010308 nuclear & particles physics, Hadron, Nuclear Theory, 7. Clean energy, 01 natural sciences, 3. Good health, Nuclear physics, Pion, Isospin, 0103 physical sciences, tagged photon spectrometer, polarization observable E, cross-sections, pion-photoproduction, baryon resonances, deuteron, MAMI, asymmetry, microtron, threshold, Neutron, ddc:530, 010306 general physics, Nucleon, Nuclear Experiment
Abstract

Photoproduction of mesons off quasi-free nucleons bound in the deuteron allows to study the electromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets. Single $\pi^0$ photoproduction off quasi-free nucleons from the deuteron was experimentally studied. Nuclear effects were investigated by a comparison of the results for free protons and quasi-free protons and used as a correction for the quasi-free neutron data. The experiment was performed at the tagged photon beam of the Mainz MAMI accelerator for photon energies between 0.45~GeV and 1.4~GeV, using an almost $4\pi$ electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. A complete kinematic reconstruction of the final state removed the effects of Fermi motion. Reaction model predictions and PWA for $\gamma n\rightarrow n\pi^{0}$, based on fits to data for the other isospin channels, disagreed between themselves and no model provided a good description of the new data. The results demonstrate clearly the importance of a measurement of the fully neutral final state for the isospin decomposition of the cross section. Model refits, for example from the Bonn-Gatchina analysis, show that the new and the previous data for the other three isospin channels can be simultaneously described when the contributions of several partial waves are modified. The results are also relevant for the suppression of the higher resonance bumps in total photoabsorption on nuclei, which are not well understood., Comment: excepted for publication in Phys. Rev. C

Published
2018
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41. Threshold π0 photoproduction on transverse polarised protons at MAMI

Author

V. Sokhoyan, S. Costanza, B. Krusche, H. J. Arends, G. M. Huber, T. Rostomyan, Lothar Tiator, V. L. Kashevarov, M. H. Sikora, M. Ostrick, L. V. Fil'kov, P. Hall-Barrientos, S. N. Prakhov, C. S. Akondi, W. Gradl, A. Polonski, S. Garni, D. I. Glazier, A. J. Sarty, A. Braghieri, D. Hornidge, B. Oussena, C. Collicott, E. J. Downie, A. Thomas, A. Mushkarenkov, V. Lisin, E. F. McNicoll, D. P. Watts, K. Livingston, Durga Paudyal, I. Keshelashvili, David Hamilton, R. Miskimen, Lilian Witthauer, N. S. Borisov, W. Meyer, M. Wolfes, P. Pedroni, V. V. Polyanski, R. Kondratiev, J. Mancel, G. Reicherz, Igor Strakovsky, A. B. Neganov, César Fernández-Ramírez, A. B. Lazarev, A. Nikolaev, G. M. Gurevich, B. M. K. Nefkens, D. G. Middleton, Th. Strub, H. Ortega, M. Dieterle, Reinhard Beck, Yu. A. Usov, O. Steffen, J. R. M. Annand, W. J. Briscoe, S. Cherepnya, P. Ott, I. J. D. MacGregor, David Manley, A. Fix, D. Werthmüller, P. P. Martel, Aron M. Bernstein, I. Supek, M. Oberle, M. Unverzagt, D. Howdle, M. Korolija, S. Schumann, and P. B. Otte

Subjects
Physics, Nuclear and High Energy Physics, Photon, Chiral perturbation theory, Scattering, media_common.quotation_subject, Asymmetry, Nuclear physics, Cross section (physics), Transverse plane, Atomic physics, Nuclear Experiment, Multipole expansion, Microtron, media_common
Abstract

Polarisation-dependent differential cross sections σ T associated with the target asymmetry T have been measured for the reaction γ p → → p π 0 with transverse target polarisation from π 0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ball / TAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for σ T have been used in combination with our previous measurements of the unpolarised cross section σ 0 and the beam asymmetry Σ for a model-independent determination of S- and P-wave multipoles in the π 0 threshold region, which includes for the first time a direct determination of the imaginary part of the E 0 + multipole.

Published
2015
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42. Measurement of double polarisation asymmetries in ω -photoproduction

Author

Frank Frommberger, V. Metag, F. Diez, M. Bichow, Ch. Hammann, T. Seifen, I. Jaegle, F. Kalischewski, D. Elsner, M. Kube, V. Crede, P. Drexler, A. Winnebeck, K. Fornet-Ponse, H. Schmieden, J. Müller, R. W. Novotny, B. Bantes, D. Walther, Ph. Hoffmeister, D. E. Bayadilov, K. Koop, U. Thoma, A. B. Gridnev, Mariana Nanova, S. Böse, A. Wilson, Yasser Maghrbi, H. Kalinowsky, Eberhard Klempt, H. Dutz, J. Hannappel, S. Runkel, H. Eberhardt, R. Ewald, Ulrich Wiedner, W. Meyer, St. Schaepe, V. A. Nikonov, T. Rostomyan, I. Keshelashvili, R. Schmitz, B. Krusche, Ch. Honisch, M. Grüner, Ch. Schmidt, A. Thiel, S. Friedrich, G. Reicherz, M. Gottschall, Friedrich Klein, Ch. Wendel, V. V. Sumachev, Wolfgang Hillert, R. Beck, Jens Hartmann, E. Gutz, S. Kammer, Th. Challand, Ch. Funke, K. Makonyi, Matthew Lang, K.-Th. Brinkmann, D. Kaiser, S. Reeve, H. van Pee, V. Kleber, D. Piontek, I. V. Lopatin, T. C. Jude, Yu. A. Beloglazov, A. V. Sarantsev, A. V. Anisovich, M. Urban, and V. Sokhoyan

Subjects
Physics, Nuclear and High Energy Physics, Photon, Meson, Partial wave analysis, Meson production, Resonance, Photon energy, Helicity, Omega, lcsh:QC1-999, Light mesons (SCB0), Nuclear physics, Baryon, Polarisation in interactions and scattering, Light mesons (SCB0), Nuclear Experiment, lcsh:Physics
Abstract

The first measurements of the beam-target-helicity-asymmetries $E$ and $G$ in the photoproduction of $\omega$-mesons off protons at the CBELSA/TAPS experiment are reported. $E$ ($G$) was measured using circularly (linearly) polarised photons and a longitudinally polarised target. $E$ was measured over the photon energy range from close to threshold ($E_\gamma = 1108$~MeV) to $E_\gamma = 2300$~MeV and $G$ at a single energy interval of $1108 < E_\gamma, Comment: 6 pages, 6 figures

Published
2015
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43. The polarization observables T , P , and H and their impact onγp→pπ0multipoles

Author

Ph. Thämer, Reinhard Beck, M. Grüner, V. Hannen, Matthew Lang, J. Herick, B. Roth, Ch. Honisch, Ch. Schmidt, K. Makonyi, K.-Th. Brinkmann, S. Reeve, H. van Pee, Eberhard Klempt, D. V. Novinski, Yu. A. Beloglazov, D. Elsner, M. Becker, Ch. Wendel, V. Crede, A. V. Sarantsev, S. Friedrich, W. Meyer, V. Metag, F. Kalischewski, Francesco Messi, R. W. Novotny, B. Krusche, Ph. Hoffmeister, St. Goertz, Lilian Witthauer, A. Käser, V. A. Nikonov, D. Piontek, I. V. Lopatin, A. V. Anisovich, J. Hannappel, P. Klassen, T. C. Jude, M. Urban, M. Dieterle, Ulrich Wiedner, V. Sokhoyan, A. Thiel, U. Thoma, Ch. Funke, Wolfgang Hillert, M. Bichow, H. Schmieden, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, K. Fornet-Ponse, S. Böse, Ch. Hammann, H. Kalinowsky, D. Walther, A. Winnebeck, A. Wilson, T. Seifen, Frank Frommberger, M. Kube, K. Koop, G. Reicherz, Friedrich Klein, R. Schmitz, O. Jahn, J. Müller, Ch. Rosenbaum, H. Dutz, H. Eberhardt, E. Gutz, I. Keshelashvili, St. Runkel, A. Berlin, T. Rostomyan, D. Kaiser, M. Gottschall, and Jens Hartmann

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Photon, Linear polarization, media_common.quotation_subject, Partial wave analysis, Electron, Polarization (waves), Asymmetry, Nuclear physics, Nuclear Experiment, Nucleon, Multipole expansion, media_common
Abstract

Data on the polarization observables T, P, and H for the reaction gamma p -> p pi(0) are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction. (C) 2015 The Authors. Published by Elsevier B.V.

Published
2015
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44. Determination of target thickness and luminosity from beam energy losses

Author

H. J. Stein, M. Hartmann, I. Keshelashvili, Y. Maeda, C. Wilkin, S. Dymov, A. Kacharava, A Khoukaz, B. Lorentz, R. Maier, T. Mersmann, S. Mikirtychiants, D. Prasuhn, R. Stassen, H. Stockhorst, H. Ströher, Yu. Valdau, and P. Wüstner

Subjects
Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The repeated passage of a coasting ion beam of a storage ring through a thin target induces a shift in the revolution frequency due to the energy loss in the target. Since the frequency shift is proportional to the beam-target overlap, its measurement offers the possibility of determining the target thickness and hence the corresponding luminosity in an experiment. This effect has been investigated with an internal proton beam of energy 2.65 GeV at the COSY-Jülich accelerator using the ANKE spectrometer and a hydrogen cluster-jet target. Possible sources of error, especially those arising from the influence of residual gas in the ring, were carefully studied, resulting in an accuracy of better than 5%. The luminosity determined in this way was used, in conjunction with measurements in the ANKE forward detector, to determine the cross section for elastic proton-proton scattering. The result is compared to published data as well as to the predictions of a phase shift solution. The practicability and the limitations of the energy-loss method are discussed.

Published
2008
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45. Determination of deuteron beam polarizations at COSY

Author

D. Chiladze, A. Kacharava, F. Rathmann, C. Wilkin, S. Barsov, J. Carbonell, S. Dymov, R. Engels, P. D. Eversheim, O. Felden, R. Gebel, V. Glagolev, K. Grigoriev, D. Gusev, M. Hartmann, F. Hinterberger, V. Hejny, A. Khoukaz, I. Keshelashvili, H. R. Koch, V. Komarov, P. Kulessa, A. Kulikov, A. Lehrach, B. Lorentz, G. Macharashvili, R. Maier, Y. Maeda, R. Menke, T. Mersmann, S. Merzliakov, M. Mikirtytchiants, S. Mikirtytchiants, A. Mussgiller, M. Nioradze, H. Ohm, D. Prasuhn, H. Rohdjeß, R. Schleichert, H. Seyfarth, E. Steffens, H. J. Stein, H. Ströher, S. Trusov, K. Ulbrich, Yu. Uzikov, A. Wrońska, and S. Yaschenko

Subjects
Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The vector (P_{z}) and tensor (P_{zz}) polarizations of a deuteron beam have been measured using elastic deuteron–carbon scattering at 75.6 MeV and deuteron-proton scattering at 270 MeV. After acceleration to 1170 MeV inside the COSY storage ring, the polarizations of the deuterons were remeasured by studying the analyzing powers of a variety of nuclear reactions. For this purpose a hydrogen cluster target was employed at the ANKE magnetic spectrometer, which is situated at an internal target position in the ring. The overall precisions obtained were about 4% for both P_{z} and P_{zz}. Though all the measurements were consistent with the absence of depolarization during acceleration, only an upper limit of about 6% could be placed on such an effect.

Published
2006
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46. Phase Locking the Spin Precession in a Storage Ring

Author

Z. Bagdasarian, A. Pesce, Martin Berz, M. Bai, D. Mchedlishvili, D. Prasuhn, Ralf Gebel, E. Valetov, Dirk Heberling, Frank Rathmann, D. Grzonka, E. J. Stephenson, M. Żurek, P. Zupranski, H. Stockhorst, V. Shmakova, Andreas Lehrach, M. D. Tabidze, L. Barion, Aleksandra Wrońska, A. Stahl, B. Lorentz, J. Hetzel, Ivan Koop, D. Eversmann, G.G. Macharashvili, A. Saleev, P. Maanen, M. Gaisser, V. Kamerdzhiev, A. Magiera, G. Guidoboni, F. Müller, W. Augustyniak, P. Wüstner, J. Pretz, F. J. Etzkorn, G. Ciullo, A. Nass, S. Mey, I. Keshelashvili, H. Ströher, A. Kulikov, Nikolai N. Nikolaev, S. Chekmenev, S. Dymov, R. Stassen, F. Trinkel, C. Weidemann, J. Slim, V. Schmidt, Yu. Valdau, A. Silenko, N.L. Lomidze, Helmut Soltner, Y. Semertzidis, Martin Rosenthal, R. Talman, Yu. N. Uzikov, Paolo Lenisa, T. Hanraths, F. Hinder, A. Vassiliev, N. Hempelmann, K. Grigoryev, V. Hejny, G. Tagliente, A.K. Kacharava, and P. Thörngren Engblom

Subjects
Accelerator Physics (physics.acc-ph), Socio-culturale, FOS: Physical sciences, General Physics and Astronomy, 01 natural sciences, Beam Polarization, Sine wave, Nuclear magnetic resonance, storage rings, 0103 physical sciences, ddc:550, Accelerators, storage rings, Beam Polarization, EDM search, 010306 general physics, Physics, Spin polarization, 010308 nuclear & particles physics, Horizontal plane, Polarization (waves), Charged particle, Electric dipole moment, EDM search, Physics::Accelerator Physics, Physics - Accelerator Physics, Radio frequency, Atomic physics, Accelerators, Storage ring
Abstract

This letter reports the successful use of feedback from a spin polarization measurement to the revolution frequency of a 0.97 GeV/$c$ bunched and polarized deuteron beam in the Cooler Synchrotron (COSY) storage ring in order to control both the precession rate ($\approx 121$ kHz) and the phase of the horizontal polarization component. Real time synchronization with a radio frequency (rf) solenoid made possible the rotation of the polarization out of the horizontal plane, yielding a demonstration of the feedback method to manipulate the polarization. In particular, the rotation rate shows a sinusoidal function of the horizontal polarization phase (relative to the rf solenoid), which was controlled to within a one standard deviation range of $\sigma = 0.21$ rad. The minimum possible adjustment was 3.7 mHz out of a revolution frequency of 753 kHz, which changes the precession rate by 26 mrad/s. Such a capability meets a requirement for the use of storage rings to look for an intrinsic electric dipole moment of charged particles.

Published
2017
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47. Study of η and η′ Photoproduction at MAMI

Author

H. J. Arends, T. Rostomyan, F. Afzal, S. Garni, P. Pedroni, A. Rajabi, Reinhard Beck, S. Costanza, M. Oberle, K. Spieker, B. Oussena, E. McNicol, A. Thomas, G. M. Huber, C. Collicott, J. C. McGeorge, D. P. Watts, D. I. Glazier, M. Unverzagt, K. Livingston, B. Strandberg, S. Gardner, A. Mushkarenkov, R. Kondratiev, Concettina Sfienti, R. Miskimen, A. Thiel, J. R. M. Annand, V. V. Polyanski, J. Wettig, G. M. Gurevich, S. Schumann, M. F. Taragin, Th. Strub, Michaela Thiel, V. L. Kashevarov, F. Cividini, B. Krusche, V. Sokhoyan, A. Neiser, L. Tiator, Igor Strakovsky, W. J. Briscoe, A. Braghieri, D. Hornidge, David Manley, V. Lisin, David Hamilton, A. Fix, D. Glowa, J. Mancell, M. Ostrick, P. B. Otte, M. Dieterle, O. Steffen, J. Linturi, W. Gradl, D. G. Middleton, I. Keshelashvili, S. N. Prakhov, P. Ott, P. P. Martel, S. Kay, M. Korolija, Ron L. Workman, Roderick M. Macrae, L. V. Fil'kov, L. Zana, G. Rosner, A. Käser, D. Howdle, C. S. Akondi, Lilian Witthauer, D. M. Schott, A. J. Sarty, S. Wagner, I. Supek, G. Reicherz, M. I. Ferretti Bondy, Z. Ahmed, P. Adlarson, E. J. Downie, D. Werthmüller, C. Mullen, A. G. Denig, Durga Paudyal, M. Wolfes, R. F. B. Codling, E. Mornacchi, I. J. D. MacGregor, and J. Robinson

Subjects
Cusp (singularity), Physics, Particle physics, Photon, Proton, 010308 nuclear & particles physics, General Physics and Astronomy, 01 natural sciences, Nuclear physics, Cross section (physics), Excited state, 0103 physical sciences, Isobar, 010306 general physics, Microtron, Crystal Ball
Abstract

The reactions γp→ηp and γp→η′p are measured from their thresholds up to the center-of-mass energy W=1.96 GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the energies in the vicinity of the η′ threshold, W=1896 MeV (Eγ=1447 MeV). Within the framework of a revised ηMAID isobar model, the cusp, in connection with a steep rise of the η′ total cross section from its threshold, can only be explained by a strong coupling of the poorly known N(1895)1/2− state to both ηp and η′p. Including the new high-accuracy results in the ηMAID fit to available η and η′ photoproduction data allows the determination of the N(1895)1/2− properties.

Published
2017
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48. First measurement of the polarization observable E and helicity-dependent cross sections in single π 0 photoproduction from quasi-free nucleons

Author

David Hamilton, T. Rostomyan, M. Bashkanov, W. Meyer, D. I. Glazier, P. B. Otte, R. Miskimen, L. Zana, Concettina Sfienti, Yu. A. Usov, O. Steffen, V. L. Kashevarov, I. Supek, A. G. Denig, P. P. Martel, V. Lisin, Durga Paudyal, K. Livingston, Reinhard Beck, Susanna Costanza, A. Polonski, M. H. Sikora, A. B. Lazarev, S. Lutterer, A. Käser, M. Wolfes, F. Afzal, R. Kondratiev, S. N. Prakhov, A. Braghieri, S. Gardner, S. Kay, Michaela Thiel, Guy Ron, Th. Strub, F. Cividini, N. S. Borisov, A. Rajabi, C. Collicott, S. Abt, W. J. Briscoe, G. M. Gurevich, D. P. Watts, Z. Ahmed, Andy Thomas, A. Thiel, E. J. Downie, E. Mornacchi, D. M. Manley, M. Korolija, G. M. Huber, H. J. Arends, D. Glowa, C. S. Akondi, Patrick Achenbach, S. Wagner, G. Reicherz, B. Krusche, A. J. Sarty, I. Keshelashvili, I. J. D. MacGregor, Igor Strakovsky, D. Werthmüller, J. R. M. Annand, M. Unverzagt, V. Sokhoyan, J. Wettig, J. Linturi, K. Spieker, M. Dieterle, M. Ostrick, J. Mancell, P. Pedroni, S. Garni, M. Biroth, N. K. Walford, P. Adlarson, P. Drexler, M. Oberle, Volker Metag, A. N. Mushkarenkov, A. Neiser, M. I. Ferretti-Bondy, D. Hornidge, Lilian Witthauer, A. B. Neganov, W. Gradl, and M. Günther

Subjects
Nuclear and High Energy Physics, Photon, Meson, Proton, Nuclear Theory, 01 natural sciences, 7. Clean energy, Nuclear physics, Recoil, 0103 physical sciences, Neutron, ddc:530, 010306 general physics, Nuclear Experiment, Physics, 010308 nuclear & particles physics, lcsh:QC1-999, 3. Good health, Nuclear cross section, Atomic physics, Nucleon, i-circle-dot, meson photoproduction, eta-photoproduction, baryon resonances, deuteron, neutrons, protons, asymmetry, photon, pairs, Crystal Ball, lcsh:Physics
Abstract

The double-polarization observable $E$ and the helicity-dependent cross sections $\sigma_{1/2}$ and $\sigma_{3/2}$ have been measured for the first time for single $\pi^{0}$ photoproduction from protons and neutrons bound in the deuteron at the electron accelerator facility MAMI in Mainz, Germany. The experiment used a circularly polarized photon beam and a longitudinally polarized deuterated butanol target. The reaction products, recoil nucleons and decay photons from the $\pi^0$ meson were detected with the Crystal Ball and TAPS electromagnetic calorimeters. Effects from nuclear Fermi motion were removed by a kinematic reconstruction of the $\pi^{0}N$ final state. A comparison to data measured with a free proton target showed that the absolute scale of the cross sections is significantly modified by nuclear final-state interaction (FSI) effects. However, there is no significant effect on the asymmetry $E$ since the $\sigma_{1/2}$ and $\sigma_{3/2}$ components appear to be influenced in a similar way. Thus, the best approximation of the two helicity-dependent cross sections for the free neutron is obtained by combining the asymmetry $E$ measured with quasi-free neutrons and the unpolarized cross section corrected for FSI effects under the assumption that the FSI effects are similar for neutrons and protons., Comment: accepted for publication in Phys. Lett. B

Published
2017
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49. Helicity-dependent cross sections and double-polarization observable E in η photoproduction from quasifree protons and neutrons

Author

H. J. Arends, V. Metag, S. Kay, David Manley, S. Garni, R. Kondratiev, J. R. M. Annand, K. Spieker, G. M. Huber, David Hamilton, K. Livingston, S. Lutterer, P. Pedroni, S. Gardner, A. Denig, N. S. Borisov, M. Biroth, F. Afzal, M. Oberle, W. Meyer, S. Wagner, C. Sfienti, F. Cividini, R. Miskimen, M. Unverzagt, G. Reicherz, A. Neiser, Igor Strakovsky, G. M. Gurevich, Z. Ahmed, Th. Strub, A. Rajabi, E. Mornacchi, D. I. Glazier, W. Gradl, I. Supek, Patrick Achenbach, I. J. D. MacGregor, M. Bashkanov, M. Günther, V. L. Kashevarov, A. Mushkarenkov, N. K. Walford, I. Keshelashvili, J. Wettig, M. Dieterle, P. Drexler, M. I. Ferretti-Bondy, M. Thiel, Yu. A. Usov, J. Mancell, O. Steffen, D. Paudyal, D. Glowa, A. Käser, P. B. Otte, Reinhard Beck, P. P. Martel, M. Korolija, W. J. Briscoe, A. Lazarev, L. Zana, V. Sokhoyan, T. Rostomyan, M. H. Sikora, C. Collicott, D. P. Watts, S. Abt, C. S. Akondi, A. B. Neganov, J. Linturi, A. J. Sarty, A. Polonski, M. Wolfes, B. Krusche, M. Ostrick, A. Thomas, A. Thiel, S. N. Prakhov, G. Ron, S. Costanza, Lilian Witthauer, A. Braghieri, D. Hornidge, V. Lisin, E. J. Downie, and D. Werthmüller

Subjects
Physics, Excitation function, Photon, 010308 nuclear & particles physics, Nuclear Theory, Bremsstrahlung, Polarization (waves), 01 natural sciences, Helicity, Nuclear physics, 0103 physical sciences, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Nucleon, Crystal Ball
Abstract

Precise helicity-dependent cross sections and the double-polarization observable E were measured for η photoproduction from quasifree protons and neutrons bound in the deuteron. The η→2γ and η→3π0→6γ decay modes were used to optimize the statistical quality of the data and to estimate systematic uncertainties. The measurement used the A2 detector setup at the tagged photon beam of the electron accelerator MAMI in Mainz. A longitudinally polarized deuterated butanol target was used in combination with a circularly polarized photon beam from bremsstrahlung of a longitudinally polarized electron beam. The reaction products were detected with the electromagnetic calorimeters Crystal Ball and TAPS, which covered 98% of the full solid angle. The results show that the narrow structure observed earlier in the unpolarized excitation function of η photoproduction off the neutron appears only in reactions with antiparallel photon and nucleon spin (σ1/2). It is absent for reactions with parallel spin orientation (σ3/2) and thus very probably related to partial waves with total spin 1/2. The behavior of the angular distributions of the helicity-dependent cross sections was analyzed by fitting them withLegendre polynomials. The results are in good agreement with a model from the Bonn-Gatchina group, which uses an interference of P11 and S11 partial waves to explain the narrow structure.

Published
2017
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50. Measurement of the ω→π0e+e− and η→e+e−γ Dalitz decays with the A2 setup at the Mainz Microtron

Author

S. N. Prakhov, Lilian Witthauer, P. Pedroni, Andy Thomas, J. Wettig, S. Garni, E. J. Downie, I. Keshelashvili, K. Spieker, E. F. McNicoll, J. Robinson, P. Drexler, V. Sokhoyan, T. Rostomyan, Michaela Thiel, A. Polonski, Z. Ahmed, R. Kondratiev, G. Rosner, D. M. Manley, G. M. Gurevich, S. Wagner, C. Mullen, C. Collicott, A. Rajabi, D. P. Watts, Lorenzo Zana, A. G. Denig, G. M. Huber, V. L. Kashevarov, Durga Paudyal, M. I. Ferretti Bondy, K. Bantawa, N. K. Walford, E. Mornacchi, V. Metag, Guy Ron, C. Sfienti, M. H. Sikora, Igor Strakovsky, W. J. Briscoe, I. J. D. MacGregor, M. Wolfes, P. P. Martel, A. N. Mushkarenkov, Roderick M. Macrae, I. V. Danilkin, J. C. McGeorge, D. Glowa, M. Unverzagt, V. Lisin, M. Ostrick, A. Neiser, D. I. Glazier, F. Cividini, K. Livingston, T. C. Jude, I. Supek, B. Strandberg, M. Korolija, S. Gardner, S. Kay, N. S. Borisov, P. Adlarson, A. B. Neganov, B. Krusche, R. A. Miskimen, P. Aguar-Bartolomé, H. J. Arends, A. Thiel, P. Ott, W. Gradl, David Hamilton, L. V. Fil'kov, H. Berghäuser, A. Käser, Yu. A. Usov, J. Linturi, D. Werthmüller, M. Dieterle, O. Steffen, A. B. Lazarev, A. Braghieri, Th. Strub, M. Biroth, D. G. Middleton, P. B. Otte, A. Nikolaev, J. R. M. Annand, F. Afzal, S. Cherepnya, D. Hornidge, M. Oberle, Susanna Costanza, and R. Beck

Subjects
Physics, 010308 nuclear & particles physics, business.industry, Scattering, Form factor (quantum field theory), Value (computer science), 01 natural sciences, Nuclear physics, Optics, 0103 physical sciences, 010306 general physics, business, Microtron, Crystal Ball
Abstract

The Dalitz decays η→e+e-γ and ω→π0e+e- have been measured in the γp→ηp and γp→ωp reactions, respectively, with the A2 tagged-photon facility at the Mainz Microtron. The value obtained for the slope parameter of the electromagnetic transition form factor of η, Λη-2=(1.97±0.11tot)GeV-2, is in good agreement with previous measurements of the η→e+e-γ and η→μ+μ-γ decays. The uncertainty obtained in the value of Λη-2 is lower than in previous results based on the η→e+e-γ decay. The value obtained for the ω slope parameter, Λωπ0-2=(1.99±0.21tot)GeV-2, is somewhat lower than previous measurements based on ω→π0μ+μ-, but the results for the ω transition form factor are in better agreement with theoretical calculations, compared to earlier experiments.

Published
2017
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