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1. Photoproduction of K+Λ(1405)→K+π0Σ0 extending to forward angles and low momentum transfer

Author

G. Scheluchin, T.C. Jude, S. Alef, P. Bauer, D. Bayadilov, R. Beck, A. Braghieri, P.L. Cole, D. Elsner, R. Di Salvo, A. Fantini, O. Freyermuth, F. Frommberger, F. Ghio, A. Gridnev, D. Hammann, J. Hannappel, K. Kohl, N. Kozlenko, A. Lapik, P. Levi Sandri, V. Lisin, G. Mandaglio, R. Messi, D. Moricciani, A. Mushkarenkov, V. Nedorezov, D. Novinskiy, P. Pedroni, A. Polonskiy, B.-E. Reitz, M. Romaniuk, H. Schmieden, V. Sumachev, and V. Tarakanov

Subjects
Strangeness photoproduction, Λ(1405), BGOOD, Physics, QC1-999
Abstract

K+Λ(1405) photoproduction has been studied at the BGOOD experiment via the all neutral decay, Λ(1405)→Σ0π0. The unique BGOOD experimental setup allows both the cross section and Λ(1405) invariant mass distribution (line shape) to be measured over a broad K+ polar angle range, extending to extreme forward K+ angles unattainable at previous experiments.Evidence is provided for the role of a triangle singularity driven by the N⁎(2030) resonance, which appears to contribute significantly to K+Λ(1405) photoproduction. This is observed in the integrated cross section which was determined with unprecedented energy resolution and supported by the angular distributions. The measured line shape is also in agreement with the previous results of CLAS and ANKE, and is consistent with two poles derived in χPT based models.

Published
2022
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2. Observation of a cusp-like structure in the γp → K+Σ0 cross section at forward angles and low momentum transfer

Author

T.C. Jude, S. Alef, P. Bauer, D. Bayadilov, R. Beck, A. Bella, J. Bieling, A. Braghieri, P.L. Cole, D. Elsner, R. Di Salvo, A. Fantini, O. Freyermuth, F. Frommberger, F. Ghio, S. Goertz, A. Gridnev, D. Hammann, J. Hannappel, K. Kohl, N. Kozlenko, A. Lapik, P. Levi Sandri, V. Lisin, G. Mandaglio, F. Messi, R. Messi, D. Moricciani, V. Nedorezov, V.A. Nikonov, D. Novinskiy, P. Pedroni, A. Polonskiy, B.-E. Reitz, M. Romaniuk, A.V. Sarantsev, G. Scheluchin, H. Schmieden, A. Stuglev, V. Sumachev, V. Vegna, V. Tarakanov, and T. Zimmermann

Subjects
Strangeness photoproduction, BGOOD, Physics, QC1-999
Abstract

The γp→K+Σ0 differential cross section at extremely forward angles was measured at the BGOOD experiment. A three-quarter drop in strength over a narrow range in energy and a strong dependence on the polar angle of the K+ in the centre-of-mass of the reaction is observed at a centre-of-mass energy of 1900 MeV. Residing close to multiple open and hidden strangeness thresholds, the structure appears consistent with meson-baryon threshold effects which may contribute to the reaction mechanism.

Published
2021
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3. 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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4. 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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5. Photoproduction of ω mesons off the proton

Author

A. Wilson, V. Crede, A.V. Anisovich, J.C.S. Bacelar, B. Bantes, O. Bartholomy, D. Bayadilov, R. Beck, Y.A. Beloglazov, K.T. Brinkmann, R. Castelijns, H. Dutz, D. Elsner, R. Ewald, F. Frommberger, M. Fuchs, Chr. Funke, R. Gregor, A. Gridnev, E. Gutz, J. Hannappel, W. Hillert, P. Hoffmeister, I. Horn, I. Jaegle, T. Jude, J. Junkersfeld, H. Kalinowsky, V. Kleber, Frank Klein, Friedrich Klein, E. Klempt, M. Kotulla, B. Krusche, M. Lang, H. Löhner, I.V. Lopatin, S. Lugert, T. Mertens, J.G. Messchendorp, V. Metag, M. Nanova, V.A. Nikonov, D. Novinski, R. Novotny, M. Ostrick, L.M. Pant, H. van Pee, M. Pfeiffer, A. Roy, A.V. Sarantsev, C. Schmidt, H. Schmieden, S. Shende, V. Sokhoyan, N. Sparks, A. Süle, V.V. Sumachev, T. Szczepanek, U. Thoma, D. Trnka, R. Varma, D. Walther, Ch. Wendel, and U. Wiedner

Subjects
Meson production, Light mesons, Baryon resonances, Photoproduction reactions, Physics, QC1-999
Abstract

The differential cross sections and unpolarized spin-density matrix elements for the reaction γp→pω were measured using the CBELSA/TAPS experiment for initial photon energies ranging from the reaction threshold to 2.5 GeV. These observables were measured from the radiative decay of the ω meson, ω→π0γ. The cross sections cover the full angular range and show the full extent of the t-channel forward rise. The overall shape of the angular distributions in the differential cross sections and unpolarized spin-density matrix elements are in fair agreement with previous data. In addition, for the first time, a beam of linearly-polarized tagged photons in the energy range from 1150 MeV to 1650 MeV was used to extract polarized spin-density matrix elements. These data were included in the Bonn–Gatchina partial wave analysis (PWA). The dominant contribution to ω photoproduction near threshold was found to be the 3/2+ partial wave, which is primarily due to the sub-threshold N(1720)3/2+ resonance. At higher energies, pomeron-exchange was found to dominate whereas π-exchange remained small. These t-channel contributions as well as further contributions from nucleon resonances were necessary to describe the entire dataset: the 1/2−, 3/2−, and 5/2+ partial waves were also found to contribute significantly.

Published
2015
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6. 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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7. Measurement of polarisation observables in Ks0Σ+ photoproduction off the proton

Author

R. Ewald, A.V. Anisovich, B. Bantes, O. Bartholomy, D. Bayadilov, R. Beck, Y.A. Beloglazov, K.-T. Brinkmann, V. Crede, H. Dutz, D. Elsner, K. Fornet-Ponse, F. Frommberger, Ch. Funke, A.B. Gridnev, E. Gutz, J. Hannappel, W. Hillert, P. Hoffmeister, I. Jaegle, O. Jahn, T.C. Jude, J. Junkersfeld, H. Kalinowsky, S. Kammer, V. Kleber, Frank Klein, Friedrich Klein, E. Klempt, B. Krusche, M. Lang, H. Löhner, I.V. Lopatin, D. Menze, T. Mertens, J.G. Messchendorp, V. Metag, M. Nanova, V.A. Nikonov, D. Novinski, R. Novotny, M. Ostrick, L. Pant, H. van Pee, A. Roy, A.V. Sarantsev, S. Schadmand, C. Schmidt, H. Schmieden, B. Schoch, S. Shende, V. Sokhoyan, A. Süle, V.V. Sumachev, T. Szczepanek, U. Thoma, D. Trnka, R. Varma, D. Walther, and Ch. Wendel

Subjects
Physics, QC1-999
Abstract

The reaction γp→KS0Σ+ is studied in the photon energy range from threshold. Linearly polarised photon beams from coherent bremsstrahlung enabled the first measurement of photon beam asymmetries in this reaction up to Eγ=1650MeV. In addition, the recoil hyperon polarisation was determined through the asymmetry in the weak decay Σ+→pπ0 up to Eγ=2250MeV. The data are compared to partial wave analyses, and the possible impact on the interpretation of a recently observed prominent structure in the cross section near the K⁎ thresholds is discussed. Keywords: Meson production, Other strange mesons, Baryon resonances (SCB0), Decays of baryons, Polarisation in interactions and scattering

Published
2014
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8. 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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9. Photoproduction of K+ Δ(1405) → K+ π0 Σ0 extending to forward angles and low momentum transfer

Author

G. Scheluchin, T.C. Jude, S. Alef, P. Bauer, D. Bayadilov, R. Beck, A. Braghieri, P.L. Cole, D. Elsner, R. Di Salvo, A. Fantini, O. Freyermuth, F. Frommberger, F. Ghio, A. Gridnev, D. Hammann, J. Hannappel, K. Kohl, N. Kozlenko, A. Lapik, P. Levi Sandri, V. Lisin, G. Mandaglio, R. Messi, D. Moricciani, A. Mushkarenkov, V. Nedorezov, D. Novinskiy, P. Pedroni, A. Polonskiy, B.-E. Reitz, M. Romaniuk, H. Schmieden, V. Sumachev, and V. Tarakanov

Subjects
Nuclear and High Energy Physics, Strangeness photoproduction, BGOOD, Lambda(1405), Settore FIS/04
Published
2022

10. 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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11. $$K^{+}\Lambda $$ photoproduction at forward angles and low momentum transfer

Author

P. Pedroni, P. Levi Sandri, A. V. Sarantsev, Patrick Bauer, M. Romaniuk, R. Messi, A. M. Lapik, Giuseppe Mandaglio, B.-E. Reitz, D. Elsner, R. Di Salvo, O. Freyermuth, A. Fantini, J. Hannappel, V. Tarakanov, Frank Frommberger, F. Ghio, N. G. Kozlenko, G. Scheluchin, V. G. Nedorezov, P. L. Cole, T. Zimmermann, D. Novinskiy, S. Goertz, D. Hammann, J. Bieling, K. Kohl, H. Schmieden, D. E. Bayadilov, A. B. Gridnev, A. Polonskiy, V. Lisin, S. Alef, V. V. Sumachev, V. A. Nikonov, A. Bella, R. Beck, T. C. Jude, V. Vegna, D. Moricciani, A. Stuglev, Francesco Messi, and A. Braghieri

Subjects
Physics, Nuclear and High Energy Physics, Spectrometer, 010308 nuclear & particles physics, Settore FIS/04, Momentum transfer, Hyperon, Lambda, 01 natural sciences, Charged particle, Momentum, Nuclear physics, Cross section (physics), Recoil, 0103 physical sciences, Nuclear Experiment, 010306 general physics
Abstract

$\gamma p \rightarrow K^+ \Lambda$ differential cross sections and recoil polarisation data from threshold for extremely forward angles are presented. The measurements were performed at the BGOOD experiment at ELSA, utilising the high angular and momentum resolution forward spectrometer for charged particle identification. The data discriminates between conflicting results in the world data set and enable extraction of the cross section as the minimum momentum transfer to the recoiling hyperon is approached., Comment: 12 pages (including a 2 page appendix), 14 figures

Published
2021
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12. 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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13. 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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14. K0SΣ0 photoproduction at the BGO-OD experiment

Author

T. C. Jude, A. Polonski, B.-E. Reitz, D. Elsner, V. Tarakanov, Christian Tillmanns, Giuseppe Mandaglio, Alessandro Braghieri, V. G. Nedorezov, Philip Cole, A. Fantini, Reinhard Beck, Paolo Levi Sandri, N. G. Kozlenko, A. M. Lapik, V. V. Sumachev, D. Moricciani, R. Messi, S. Alef, Rachele Di Salvo, D. Hammann, J. Hannappel, Francesco Oliver, K. Kohl, Valery Lisin, H. Schmieden, A. B. Gridnev, Patrick Bauer, O. Freyermuth, M. Romaniuk, D. V. Novinsky, G. Scheluchin, and P. Pedroni

Subjects
Physics, Spectrometer, Meson, 010308 nuclear & particles physics, QC1-999, Settore FIS/04, Momentum transfer, Nuclear Theory, Strangeness, 01 natural sciences, Nuclear physics, Dipole, 0103 physical sciences, Neutron, High Energy Physics::Experiment, 010306 general physics, Nucleon, Nuclear Experiment, Excitation
Abstract

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremsstrahlung photon beam to investigate the excitation structure of the nucleon via meson photoproduction. The setup with a BGO calorimeter surrounding the target and an open dipole spectrometer covering the for ward region is ideally suited for investigating low momentum transfer processes, in particular in strangeness photoproduction. The associated photoproduction of K0S and hyperons is essential to understand the role of K* exchange mech anisms. A cusp-like structure observed in the yp → K0SΣ+ reaction at the K* threshold is described by models including dynamically generated resonances from vector meson-baryon interactions. Such interactions are pre dicted to give a peak like structure in K0SΣ0 photoproduction off the neutron. A very preliminary cross section is determined and compared to the prediction, the results appear to support the model

Published
2020

15. Strangeness photoproduction at the BGO-OD experiment

Author

H. Schmieden, D. Elsner, A. B. Gridnev, N. G. Kozlenko, V. G. Nedorezov, Patrick Bauer, A. M. Lapik, T. C. Jude, G. Scheluchin, Christian Tillmanns, Valery Lisin, Alessandro Braghieri, S. Alef, Philip Cole, Paolo Levi Sandri, M. Romaniuk, B.-E. Reitz, V. Tarakanov, D. V. Novinsky, R. Messi, D. Hammann, F. Ghio, P. Pedroni, Rachele Di Salvo, D. Moricciani, O. Freyermuth, J. Hannappel, A. Polonski, K. Kohl, A. Fantini, Giuseppe Mandaglio, Reinhard Beck, and V. V. Sumachev

Subjects
Particle physics, QC1-999, Nuclear Theory, FOS: Physical sciences, Strangeness, strangeness photoproduction, 01 natural sciences, Charm quark, Momentum, Nuclear physics, 0103 physical sciences, Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment, Physics, Spectrometer, 010308 nuclear & particles physics, BGO-OD, Settore FIS/04, Momentum transfer, Pentaquark, Λ(1405), High Energy Physics::Experiment, Nucleon, Excitation
Abstract

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremsstrahlung photon beam to investigate the excitation structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play an important role. This also allows access to low momentum exchange kinematics where extended, molecular structure may manifest in reaction mechanisms. First key results at low $t$ indicate a cusp-like structure in $K^+\Sigma^0$ photoproduction at $W = 1900$\,MeV, line shapes and differential cross sections for $K^+\Lambda$(1405)$\rightarrow K^+\Sigma^0\pi^0$, and a peak structure in $K^0_S\Sigma^0$ photoproduction. The peak in the $K^0_S\Sigma^0$ channel appears consistent with meson-baryon generated states, where equivalent models have been used to describe the $P_C$ pentaquark candidates in the heavy charmed quark sector., Comment: Proceedings of The 12th International Workshop on the Physics of Excited Nucleons (NSTAR 2019)

Published
2020

16. 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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17. η’ beam asymmetry at threshold using the BGO-OD experiment

Author

Philip Cole, D. V. Novinsky, D. Hammann, A. M. Lapik, T. C. Jude, G. Scheluchin, Reinhard Beck, D. Moricciani, V. V. Sumachev, K. Kohl, Paolo Levi Sandri, V. G. Nedorezov, Patrick Bauer, R. Messi, M. Romaniuk, A. Fantini, Christian Tillmanns, Alessandro Braghieri, Valery Lisin, Rachele Di Salvo, A. Polonski, Giuseppe Mandaglio, J. Hannappel, O. Freyermuth, N. G. Kozlenko, P. Pedroni, H. Schmieden, A. B. Gridnev, V. Tarakanov, S. Alef, B.-E. Reitz, F. Ghio, and D. Elsner

Subjects
Physics, Proton, Meson, Spectrometer, 010308 nuclear & particles physics, Settore FIS/04, media_common.quotation_subject, QC1-999, 01 natural sciences, Signal, Resonance (particle physics), Asymmetry, Charged particle, Nuclear physics, 0103 physical sciences, 010306 general physics, Nuclear Experiment, Beam (structure), media_common
Abstract

The unexpected nodal structure of the beam asymmetry recently reported by the GRAAL collaboration in η′ photoproduction very close to threshold could be explained by a previously unobserved narrow resonance. The BGO-OD experiment is ideally suited to verify this measurement via the detection of forward going charged particles which in the threshold region of interest allows the identification of the reaction γp → η′ p solely based on the proton going in the forward direction. This yields unprecedented statistics if, in the missing mass analysis of the η′ meson, the background can be sufficiently well controlled. Preliminary results using a linearly polarised photon beam are shown. The reaction γp → η′ p was identified in the BGO forward spectrometer, with simulated data used to seperate signal and background.

Published
2020

18. Observation of a cusp-like structure in the γp → K+Σ0 cross section at forward angles and low momentum transfer

Author

D. Elsner, P. Pedroni, N. G. Kozlenko, Giuseppe Mandaglio, R. Messi, V. G. Nedorezov, Patrick Bauer, V. A. Nikonov, P. Levi Sandri, R. Di Salvo, S. Alef, B.-E. Reitz, A. V. Sarantsev, J. Bieling, J. Hannappel, M. Romaniuk, R. Beck, F. Ghio, A. M. Lapik, V. V. Sumachev, V. Lisin, D. Hammann, Francesco Messi, H. Schmieden, D. E. Bayadilov, A. B. Gridnev, Frank Frommberger, A. Bella, A. Polonskiy, V. Tarakanov, O. Freyermuth, A. Fantini, D. Novinskiy, S. Goertz, A. Stuglev, P. L. Cole, K. Kohl, A. Braghieri, T. C. Jude, T. Zimmermann, G. Scheluchin, D. Moricciani, and V. Vegna

Subjects
Cusp (singularity), Physics, Nuclear and High Energy Physics, Reaction mechanism, Strangeness photoproduction, 010308 nuclear & particles physics, QC1-999, Settore FIS/04, Drop (liquid), Momentum transfer, BGOOD, Structure (category theory), Strangeness, 01 natural sciences, Cross section (physics), 0103 physical sciences, Polar coordinate system, Atomic physics, Nuclear Experiment, 010306 general physics
Abstract

The γ p → K + Σ 0 differential cross section at extremely forward angles was measured at the BGOOD experiment. A three-quarter drop in strength over a narrow range in energy and a strong dependence on the polar angle of the K + in the centre-of-mass of the reaction is observed at a centre-of-mass energy of 1900 MeV. Residing close to multiple open and hidden strangeness thresholds, the structure appears consistent with meson-baryon threshold effects which may contribute to the reaction mechanism.

Published
2021
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19. 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

20. Strangeness Photoproduction at the BGO-OD Experiment

Author

D. Moricciani, K. Kohl, V. G. Nedorezov, D. Novinskiy, P. Levi Sandri, N. G. Kozlenko, A. Polonski, Giuseppe Mandaglio, A. Fantini, P. Cole, R. Messi, V. Lisin, R. Di Salvo, G. Scheluchin, V. Tarakanov, Christian Tillmanns, A. M. Lapik, D. Elsner, O. Freyermuth, D. Hammann, J. Hannappel, Reinhard Beck, V. V. Sumachev, S. Alef, H. Schmieden, A. B. Gridnev, B.-E. Reitz, F. Ghio, T. C. Jude, Patrick Bauer, M. Romaniuk, and P. Pedroni

Subjects
Physics, Settore FIS/01, Nuclear and High Energy Physics, Calorimeter (particle physics), Spectrometer, Nuclear Theory, Momentum transfer, Bremsstrahlung, Elementary particle, Strangeness, Tracking (particle physics), Nuclear physics, Nuclear Experiment, Nucleon
Abstract

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremstrahlung photon beam to investigate the excitation structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play an important role. This also allows access to a kinematic region where extended, molecular structure may manifest in reaction mechanisms. The extensive strangeness photoproduction programme includes the photoproduction of neutral and charged kaons using both hydrogen and deuterium targets.

Published
2019

21. 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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22. K+Λ(1405) photoproduction at the BGO-OD experiment

Author

Valery Lisin, Reinhard Beck, D. Elsner, A. Fantini, D. V. Novinsky, Giuseppe Mandaglio, K. Kohl, V. G. Nedorezov, V. V. Sumachev, G. Scheluchin, Paolo Levi Sandri, T. C. Jude, Mariia Romaniuk, B.-E. Reitz, V. Tarakanov, Christian Tillmanns, A. Polonski, O. Freyermuth, Patrick Bauer, Alessandro Braghieri, P. Pedroni, Philip Cole, A. M. Lapik, J. Hannappel, N. G. Kozlenko, Dario Moricciani, F. Ghio, D. Hammann, R. Messi, H. Schmieden, Rachele Di Salvo, A. B. Gridnev, and S. Alef

Subjects
Physics, Spectrometer, 010308 nuclear & particles physics, Settore FIS/04, QC1-999, High Energy Physics::Phenomenology, Constituent quark, Large aperture, 01 natural sciences, Measure (mathematics), Calorimeter, Crystal, Nuclear physics, 0103 physical sciences, High Energy Physics::Experiment, Charm (quantum number), Nuclear Experiment, 010306 general physics
Abstract

Since the discovery of the Λ(1405), it remains poorly described by conventional constituent quark models, and it is a candidate for having an “exotic” meson-baryon or “penta-quark” structure, similar to states recently reported in the hidden charm sector.The Λ(1405) can be produced in the reactionγpK+Λ(1405). The pure I=0 decay mode into Σ0π0is prohibited for the mass-overlapping Σ(1385). Combining a large aperture forward magnetic spectrometer and a central BGO crystal calorimeter, the BGO-OD experiment is ideally suited to measure this decay with theK+in the forward direction. Preliminary results are presented.*Supported by DFG (PN 388979758, 405882627)

Published
2020
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23. Erratum to: Strangeness Photoproduction at the BGO-OD Experiment

Author

J. Hannappel, Giuseppe Mandaglio, T. C. Jude, O. Freyermuth, P. Pedroni, B.-E. Reitz, D. Moricciani, D. Elsner, A. Polonski, A. Fantini, N. G. Kozlenko, F. Ghio, Patrick Bauer, Christian Tillmanns, D. Novinskiy, P. Levi Sandri, A. M. Lapik, V. V. Sumachev, K. Kohl, S. Alef, R. Beck, H. Schmieden, A. B. Gridnev, R. Messi, R. Di Salvo, P. Cole, V. Tarakanov, M. Romaniuk, V. Lisin, G. Scheluchin, V. G. Nedorezov, and D. Hammann

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Strangeness
Published
2020
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24. 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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25. Strangeness photoproduction at the BGO-OD experiment

Author

V. Metag, V. Tarakanov, R. Joosten, O. Freyermuth, S. Friedrich, D. Burdeynyi, K. Kohl, Francesco Messi, A. Polonski, D. Novinskiy, Hans-Georg Zaunick, G. Gervino, J. Hannappel, J. Bieling, R. Messi, A. Fantini, Wolfgang Hillert, D. Hammann, K.-T. Brinkmann, D. Moricciani, P. L. Cole, R. Jahn, P. Pedroni, B. Krusche, Giuseppe Mandaglio, V. Lisin, D. Elsner, G. Scheluchin, A. Stugelev, A. M. Lapik, Frank Klein, R. Di Salvo, A. Bella, A. Braghieri, Reinhard Beck, Frank Frommberger, T. Zimmermann, A. N. Mushkarenkov, V. V. Sumachev, P. Levi Sandri, I. V. Lopatin, T. C. Jude, Patrick Bauer, E. Gutz, V. G. Nedorezov, D. Walther, S. Boese, V. Vegna, M. Romaniuk, S. Alef, B.-E. Reitz, F. Ghio, H. Schmieden, D. E. Bayadilov, A. B. Gridnev, and Mariana Nanova

Subjects
Settore FIS/01, Physics, Calorimeter (particle physics), Meson, Nuclear Theory, Momentum transfer, Hadron, Constituent quark, Strangeness, strangeness photoproduction, Baryon, Nuclear physics, Nuclear Experiment, Nucleon
Abstract

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremstrahlung photon beam to investigate the excitation spectrum of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating the photoproduction of hadrons of non-zero strangeness. The high momentum resolution at forward angles covers a kinematic region where t-channel exchange mechanisms play a dominant role. Access to this low momentum transfer region also allows the investigation of degrees of freedom not derived from constituent quark models, for example, the role of (vector) meson - baryon interactions and dynamically generated states in photoproduction reactions. Data taking for the first part of an extensive physics programme is complete and preliminary results and ongoing analysis are presented. (Less)

Published
2018
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26. 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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27. 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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28. Photoproduction of eta mesons from the neutron: cross sections and double polarization observable E

Author

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

Subjects
Excitation function, Physics, Nuclear and High Energy Physics, Meson, 010308 nuclear & particles physics, media_common.quotation_subject, Nuclear Theory, FOS: Physical sciences, Observable, Polarization (waves), 01 natural sciences, Helicity, Asymmetry, Nuclear physics, Deuterium, 0103 physical sciences, ddc:530, High Energy Physics::Experiment, Neutron, Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment, media_common
Abstract

Photoproduction of $\eta$ mesons from neutrons} \abstract{Results from measurements of the photoproduction of $\eta$ mesons from quasifree protons and neutrons are summarized. The experiments were performed with the CBELSA/TAPS detector at the electron accelerator ELSA in Bonn using the $\eta\to3\pi^{0}\to6\gamma$ decay. A liquid deuterium target was used for the measurement of total cross sections and angular distributions. The results confirm earlier measurements from Bonn and the MAMI facility in Mainz about the existence of a narrow structure in the excitation function of $\gamma n\rightarrow n\eta$. The current angular distributions show a forward-backward asymmetry, which was previously not seen, but was predicted by model calculations including an additional narrow $P_{11}$ state. Furthermore, data obtained with a longitudinally polarized, deuterated butanol target and a circularly polarized photon beam were analyzed to determine the double polarization observable $E$. Both data sets together were also used to extract the helicity dependent cross sections $\sigma_{1/2}$ and $\sigma_{3/2}$. The narrow structure in the excitation function of $\gamma n\rightarrow n\eta$ appears associated with the helicity-1/2 component of the reaction.

Published
2017
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29. Measurement of polarisation observables inKs0Σ+photoproduction off the proton

Author

Volker Metag, H. Dutz, S. Schadmand, T. Mertens, T. C. Jude, Matthew Lang, H. Schmieden, R. Ewald, D. E. Bayadilov, K. Fornet-Ponse, A. B. Gridnev, Mariana Nanova, D. Walther, A. Suele, V. Sokhoyan, Friedrich Klein, J. G. Messchendorp, V. Kleber, T. Szczepanek, M. Ostrick, Herbert Löhner, A. Roy, I. Jaegle, K.-T. Brinkmann, I. V. Lopatin, Ch. Schmidt, R. Varma, V. Crede, E. Gutz, D. Trnka, O. Jahn, R. Beck, Wolfgang Hillert, Lalit Mohan Pant, B. Bantes, S. Kammer, Ch. Funke, D. Elsner, Yu. A. Beloglazov, A. V. Sarantsev, V. A. Nikonov, R. W. Novotny, A. V. Anisovich, Ph. Hoffmeister, B. Schoch, D. Menze, Eberhard Klempt, J. Hannappel, Ch. Wendel, V. V. Sumachev, U. Thoma, J. Junkersfeld, S. Shende, H. Kalinowsky, D. V. Novinski, H. van Pee, B. Krusche, O. Bartholomy, Frank Klein, and Frank Frommberger

Subjects
Physics, Nuclear physics, Nuclear and High Energy Physics, Photon, Proton, Partial wave analysis, Hyperon, Bremsstrahlung, Photon energy, Nuclear Experiment, Nucleon, 7. Clean energy, Sigma baryon
Abstract

The reaction γ p → K S 0 Σ + is studied in the photon energy range from threshold. Linearly polarised photon beams from coherent bremsstrahlung enabled the first measurement of photon beam asymmetries in this reaction up to E γ = 1650 MeV . In addition, the recoil hyperon polarisation was determined through the asymmetry in the weak decay Σ + → p π 0 up to E γ = 2250 MeV . The data are compared to partial wave analyses, and the possible impact on the interpretation of a recently observed prominent structure in the cross section near the K ⁎ thresholds is discussed.

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

Author

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

Subjects
Physics, education.field_of_study, Nuclear and High Energy Physics, Meson, Hadron, Population, Nuclear Theory, Carbon-12, Elementary particle, lcsh:QC1-999, Pion, Bound state, Atomic physics, Nucleon, education, Nuclear Experiment, lcsh:Physics
Abstract

In a search for $\omega$ mesic states, the production of $\omega$-mesons in coincidence with forward going protons has been studied in photon induced reactions on $^{12}$C for incident photon energies of 1250 - 3100 MeV. The $\pi^0 \gamma$ pairs from decays of bound or quasi-free $\omega$-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 $\pi^0 \gamma$ pairs, which would indicate the population and decay of bound $\omega~^{11}$B states, are not observed. The $\pi^0 \gamma$ cross section of 0.3 nb/MeV/sr 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 $\omega$-meson. A comparison of the measured total energy distribution with calculations suggests the real part $V_0$ of the $\omega~^{11}$B potential to be small and only weakly attractive with $V_0(\rho=\rho_0) = -15\pm$ 35(stat) $\pm$20(syst) MeV in contrast to some theoretical predictions of attractive potentials with a depth of 100 - 150 MeV., Comment: 13 pages, 8 figures

Published
2014
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31. Determination of the eta '-nucleus optical potential

Author

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

Subjects
Physics, Excitation function, Nuclear and High Energy Physics, Photon, Meson, 010308 nuclear & particles physics, Hadron, Nuclear Theory, Elementary particle, Electron, Nuclear matter, 01 natural sciences, 0103 physical sciences, Bound state, High Energy Physics::Experiment, Atomic physics, 010306 general physics, Nuclear Experiment
Abstract

The excitation function and momentum distribution of $\eta^\prime$ mesons have been measured in photon induced reactions on $^{12}{}$C in the energy range of 1250-2600 MeV. The experiment was performed with tagged photon beams from the ELSA electron accelerator using the Crystal Barrel and TAPS detectors. The data are compared to model calculations to extract information on the sign and magnitude of the real part of the $\eta^\prime$-nucleus potential. Within the model, the comparison indicates an attractive potential of -($37 \pm 10(stat)\pm10(syst)$) MeV depth at normal nuclear matter density. Since the modulus of this depth is larger than the modulus of the imaginary part of the $\eta^\prime$-nucleus potential of -($10\pm2.5$) MeV, determined by transparency ratio measurements, a search for resolved $\eta^\prime$-bound states appears promising., Comment: 13 pages, 6 figures

Published
2013

32. Momentum dependence of the imaginary part of the $\omega$- and $\eta^\prime$-nucleus optical potential

Author

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

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Photon, Meson, 010308 nuclear & particles physics, High Energy Physics::Phenomenology, Nuclear Theory, 01 natural sciences, Omega, Momentum, 0103 physical sciences, Bound state, Production (computer science), ddc:530, High Energy Physics::Experiment, Absorption (logic), 010306 general physics, Nuclear Experiment, Glauber
Abstract

The photoproduction of $\omega$ and $\eta^\prime$ mesons off carbon and niobium nuclei has been measured as a function of the meson momentum for incident photon energies of 1.2-2.9 GeV at the electron accelerator ELSA. The mesons have been identified via the $\omega \rightarrow \pi^0 \gamma \rightarrow 3 \gamma$ and $\eta^\prime\rightarrow \pi^0 \pi^0\eta \rightarrow 6 \gamma$ decays, respectively, registered with the CBELSA/TAPS detector system. From the measured meson momentum distributions the momentum dependence of the transparency ratio has been determined for both mesons. Within a Glauber analysis the in-medium $\omega$ and $\eta^\prime$ widths and the corresponding absorption cross sections have been deduced as a function of the meson momentum. The results are compared to recent theoretical predictions for the in-medium $\omega$ width and $\eta^\prime$-N absorption cross sections. The energy dependence of the imaginary part of the $\omega$- and $\eta^\prime$-nucleus optical potential has been extracted. The finer binning of the present data compared to the existing data allows a more reliable extrapolation towards the production threshold. The modulus of the imaginary part of the $\eta^\prime$ nucleus potential is found to be about three times smaller than recently determined values of the real part of the $\eta^\prime$-nucleus potential, which makes the $\eta^\prime$ meson a suitable candidate for the search for meson-nucleus bound states. For the $\omega$ meson, the modulus of the imaginary part near threshold is comparable to the modulus of the real part of the potential. As a consequence, only broad structures can be expected which makes the observation of $\omega$ mesic states very difficult experimentally., Comment: 10 pages, 8 figures

Published
2016
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33. Polarised Photon Beams for the BGO-OD Experiment at ELSA

Author

P. Levi Sandri, S. Friedrich, B.-E. Reitz, V. Ganenko, D. Elsner, Francesco Messi, R. Jahn, T. C. Jude, F. Ghio, K.-T. Brinkmann, V. G. Nedorezov, D. P. Watts, M. Becker, D. Moricciani, A. Bella, D. Walther, P. Pedroni, V. Vegna, R. Joosten, A. M. Lapik, H. Schmieden, D. E. Bayadilov, P. Bielefeldt, A. B. Gridnev, Mariana Nanova, S. Boese, T. Zimmermann, A. Stugelev, V. De Leo, E. Gutz, V. Metag, Wolfgang Hillert, S. Alef, P. Hartmann, B. Krusche, Giuseppe Mandaglio, G. Gervino, T. Rostomyan, M. Romaniuk, A. Braghieri, G. Scheluchin, G. Giardina, J. Hannappel, I. V. Lopatin, H. Dutz, A. Fantini, V. Tarakanov, P. L. Cole, N. V. Rudnev, Reinhard Beck, O. Freyermuth, Hans-Georg Zaunick, V. V. Sumachev, A. Ignatov, C. Schaerf, D. Hammann, Francesca Curciarello, K. Koop, R. Messi, Frank Frommberger, A. N. Mushkarenkov, D. Novinskiy, S. Goertz, Frank Klein, and R. Di Salvo

Subjects
Physics, Nuclear physics, Elastic scattering, law, Bremsstrahlung, Polarimeter, Particle accelerator, Electron, Nuclear Experiment, Polarization (waves), Nucleon, Electromagnetic radiation, law.invention
Abstract

The new BGO-OD experiment at the electron accelerator ELSA, of the University of Bonn, is designed to study the reaction dynamics of nucleon excitations in meson photoproduction. It consists of a central BGO calorimeter with a magnetic spectrometer in forward direction. The physics programme includes the measurement of polarisation observables using linearly and circularly polarised photon beams. Linear polarisation is obtained by coherent bremsstrahlung off a diamond crystal, and circular polarisation is obtained via bremsstrahlung from longitudinally polarised electrons. The degree of linear polarisation is determined from the bremsstrahlung spectrum itself. To determine the polarisation of the circularly polarised photon beam, the polarisation of the electron beam is measured by a Moller polarimeter. As a preliminary consistency check, the (linear) polarisation observable, Σ, was compared to world data for π^0 and η photoproduction. To determine the degree of circular polarisation, a Moller polarimeter was setup and first measurements of the electron beam polarisation performed.

Published
2016
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34. Determination of the real part of the η ′ -Nb optical potential

Author

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

Subjects
Excitation function, Physics, Meson, 010308 nuclear & particles physics, Nuclear Theory, Bremsstrahlung, Particle accelerator, Nuclear matter, 01 natural sciences, law.invention, Nuclear physics, Momentum, law, Excited state, 0103 physical sciences, Bound state, High Energy Physics::Experiment, ddc:530, Atomic physics, 010306 general physics, Nuclear Experiment
Abstract

The excitation function and momentum distribution of {\eta}' mesons have been measured in photoproduction off 93^Nb in the energy range of 1.2-2.9 GeV. The experiment has been performed with the combined Crystal Barrel and MiniTAPS detector system, using tagged photon beams from the ELSA electron accelerator. Information on the sign and magnitude of the real part of the {\eta}'-Nb potential has been extracted from a comparison of the data with model calculations. An attractive potential of -(41 \pm 10(stat) \pm 15(syst)) MeV depth at normal nuclear matter density is deduced within model uncertainties. This value is consistent with the potential depth of -(37 \pm 10(stat) \pm 10(syst)) MeV obtained in an earlier measurement for a light nucleus (carbon). This relatively shallow {\eta}'-nucleus potential will make the search for {\eta}'-nucleus bound states more difficult., Comment: 9 pages, 6 figures

Published
2016
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35. Commissioning and initial experimental program of the BGO-OD experiment at ELSA

Author

D. Elsner, K. Koop, V. G. Nedorezov, D. Geffers, Wolfgang Hillert, R. Jahn, H. Dutz, H. Schmieden, D. Moricciani, D. E. Bayadilov, R. Messi, T. C. Jude, G. Scheluchin, Friedrich Klein, T. Rostomyan, A. B. Gridnev, A. Ignatov, Mariana Nanova, M. Becker, S. Böse, V. Tarakanov, G. Gervino, P. Levi Sandri, D. Walther, J. Knaust, D. P. Watts, E. Gutz, P. Bielefeldt, Reinhard Beck, S. Friedrich, A. Braghieri, A. M. Lapik, N. Rudnev, Francesco Messi, B.-E. Reitz, A. Stugelev, V. Ganenko, S. Görtz, Hans-Georg Zaunick, Patrick Bauer, F. Ghio, V. V. Sumachev, C. Schaerf, I. V. Lopatin, D. Hammann, Volker Metag, K.-T. Brinkmann, S. Alef, T. Zimmermann, V. Vegna, P. Cole, R. Joosten, P. Pedroni, K. Kohl, A. Fantini, B. Krusche, Giuseppe Mandaglio, M. Romaniuk, O. Freyermuth, A. Bella, J. Hannappel, D. Novinskiy, A. Mushkarenkov, R. Di Salvo, and Frank Frommberger

Subjects
Photon, Meson, QC1-999, Hadron, Nuclear Theory, Elementary particle, Astrophysics, radiation detection, 01 natural sciences, Particle detector, Nuclear physics, Hadron Physics, 0103 physical sciences, Nuclear Physics, Hadron Physics, radiation detection, 010306 general physics, Nuclear Experiment, Nuclear Physics, Physics, 010308 nuclear & particles physics, Settore FIS/04, Detector, High Energy Physics::Phenomenology, Hyperon, Baryon, High Energy Physics::Experiment
Abstract

BGO-OD is a new meson photoproduction experiment at the ELSA facility of Bonn University. It aims at the investigation of non strange and strange baryon excitations, and is especially designed to be able to detect weekly bound meson-baryon type structures. The setup for the BGO-OD experiment is presented, the characteristics of the photon beam and the detector performances are shown and the initial experimental program is discussed.

Published
2016

36. Double-polarization observable G in neutral-pion photoproduction off the proton

Author

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

Subjects
Physics, Nuclear and High Energy Physics, Photon, Proton, 010308 nuclear & particles physics, Nuclear Theory, Bremsstrahlung, Diamond, FOS: Physical sciences, Observable, Photon energy, engineering.material, Polarization (waves), 01 natural sciences, Nuclear physics, Pion, 0103 physical sciences, engineering, ddc:530, Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment
Abstract

This paper reports on a measurement of the double-polarization observable G in $\pi^0$ photoproduction off the proton using the CBELSA/TAPS experiment at the ELSA accelerator in Bonn. The observable G is determined from reactions of linearly-polarized photons with longitudinally-polarized protons. The polarized photons are produced by bremsstrahlung off a properly oriented diamond radiator. A frozen spin butanol target provides the polarized protons. The data cover the photon energy range from 617 to 1325 MeV and a wide angular range. The experimental results for G are compared to predictions by the Bonn-Gatchina (BnGa), J\"ulich-Bonn (J\"uBo), MAID and SAID partial wave analyses. Implications of the new data for the pion photoproduction multipoles are discussed.

Published
2016
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37. Strangeness Photoproduction at the BGO-OD Experiment

Author

V. G. Nedorezov, Frank Frommberger, V. Metag, A. Ignatov, Hans-Georg Zaunick, V. Tarakanov, T. Zimmermann, N. V. Rudnev, D. Hammann, D. Moricciani, P. Bielefeldt, Wolfgang Hillert, P. Pedroni, A. N. Mushkarenkov, D. P. Watts, V. Vegna, O. Freyermuth, D. Novinskiy, D. Elsner, Francesca Curciarello, S. Goertz, V. De Leo, B. Krusche, Giuseppe Mandaglio, R. Messi, M. Romaniuk, H. Dutz, A. Braghieri, B.-E. Reitz, P. Levi Sandri, A. Bella, V. Ganenko, Reinhard Beck, P. Hartmann, Frank Klein, R. Di Salvo, T. Rostomyan, G. Scheluchin, E. Gutz, A. Fantini, D. Walther, S. Friedrich, F. Ghio, Francesco Messi, V. V. Sumachev, S. Boese, P. L. Cole, R. Joosten, S. Alef, G. Giardina, R. Jahn, K. Koop, J. Hannappel, T. C. Jude, M. Becker, I. V. Lopatin, A. Stugelev, K.-T. Brinkmann, A. M. Lapik, G. Gervino, H. Schmieden, D. E. Bayadilov, A. B. Gridnev, and Mariana Nanova

Subjects
Meson, Nuclear Theory, FOS: Physical sciences, Electron, Strangeness, Tracking (particle physics), nucl-ex, 01 natural sciences, Nuclear physics, photoproduction, dynamically generated resonance, strangeness, BGO-OD, 0103 physical sciences, Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment, Physics, Settore FIS/01, Calorimeter (particle physics), Spectrometer, 010308 nuclear & particles physics, photoproduction, dynamically generated resonance, strangeness, BGO-OD, High Energy Physics::Experiment, Nucleon, Beam (structure)
Abstract

BGO-OD is a newly commissioned experiment to investigate the internal structure of the nucleon, using an energy tagged bremsstrahlung photon beam at the ELSA electron facility. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating meson photoproduction. The extensive physics programme for open strangeness photoproduction is introduced, and preliminary analysis presented., 6 pages, 4 figures. Proceedings for the 10th International Workshop on the Physics of Excited Nucleons (NSTAR2015)

Published
2016
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39. Anomaly in the KS0Σ+ photoproduction cross section off the proton at the K⁎ threshold

Author

Volker Metag, Wolfgang Hillert, S. Shende, A. Suele, D. Walther, S. Kammer, Ch. Funke, Frank Frommberger, J. Hannappel, H. van Pee, D. Elsner, B. Krusche, D. Menze, R. W. Novotny, Ph. Hoffmeister, O. Bartholomy, B. Schoch, H. Schmieden, U. Thoma, D. E. Bayadilov, A. B. Gridnev, E. Gutz, A. Roy, Mariana Nanova, T. Szczepanek, V. Sokhoyan, Eberhard Klempt, Yu. A. Beloglazov, Ch. Wendel, R. Beck, V. V. Sumachev, Frank Klein, J. Junkersfeld, K. T Brinkmann, H. Kalinowsky, Matthew Lang, S. Schadmand, M. Ostrick, V. Kleber, R. Varma, L. M. Pant, H. Dutz, V. Crede, T. Mertens, Herbert Löhner, R. Ewald, B. Bantes, D. V. Novinski, D. Trnka, Ch. Schmidt, O. Jahn, K. Fornet-Ponse, I. Jaegle, Friedrich Klein, I. V. Lopatin, T. C. Jude, and J. G. Messchendorp

Subjects
Physics, Nuclear physics, Baryon, Nuclear and High Energy Physics, Cross section (physics), Proton, Meson, Hadron, Elementary particle, Strangeness, Nucleon
Abstract

The γ + p → K 0 + Σ + photoproduction reaction is investigated in the energy region from threshold to E γ = 2250 MeV . The differential cross section exhibits increasing forward-peaking with energy, but only up to the K ⁎ threshold. Beyond, it suddenly returns to a flat distribution with the forward cross section dropping by a factor of four. In the total cross section a pronounced structure is observed between the K ⁎ Λ and K ⁎ Σ thresholds.

Published
2012
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40. The COMPASS experiment at CERN

Author

P. Abbon, E. Albrecht, V.Yu. Alexakhin, Yu. Alexandrov, G.D. Alexeev, M.G. Alekseev, A. Amoroso, H. Angerer, V.A. Anosov, B. Badełek, F. Balestra, J. Ball, J. Barth, G. Baum, M. Becker, Y. Bedfer, P. Berglund, C. Bernet, R. Bertini, M. Bettinelli, R. Birsa, J. Bisplinghoff, P. Bordalo, M. Bosteels, F. Bradamante, A. Braem, A. Bravar, A. Bressan, G. Brona, E. Burtin, M.P. Bussa, V.N. Bytchkov, M. Chalifour, A. Chapiro, M. Chiosso, P. Ciliberti, A. Cicuttin, M. Colantoni, A.A. Colavita, S. Costa, M.L. Crespo, P. Cristaudo, T. Dafni, N. d’Hose, S. Dalla Torre, C. d’Ambrosio, S. Das, S.S. Dasgupta, E. Delagnes, R. De Masi, P. Deck, N. Dedek, D. Demchenko, O.Yu. Denisov, L. Dhara, V. Diaz, N. Dibiase, A.M. Dinkelbach, A.V. Dolgopolov, A. Donati, S.V. Donskov, V.A. Dorofeev, N. Doshita, D. Durand, V. Duic, W. Dünnweber, A. Efremov, P.D. Eversheim, W. Eyrich, M. Faessler, V. Falaleev, P. Fauland, A. Ferrero, L. Ferrero, M. Finger, H. Fischer, C. Franco, J. Franz, F. Fratnik, J.M. Friedrich, V. Frolov, U. Fuchs, R. Garfagnini, L. Gatignon, F. Gautheron, O.P. Gavrichtchouk, S. Gerassimov, R. Geyer, J.M. Gheller, A. Giganon, M. Giorgi, B. Gobbo, S. Goertz, A.M. Gorin, F. Gougnaud, S. Grabmüller, O.A. Grajek, A. Grasso, B. Grube, A. Grünemaier, A. Guskov, F. Haas, R. Hagemann, J. Hannappel, D. von Harrach, T. Hasegawa, J. Heckmann, S. Hedicke, F.H. Heinsius, R. Hermann, C. Heß, F. Hinterberger, M. von Hodenberg, N. Horikawa, S. Horikawa, I. Horn, C. Ilgner, A.I. Ioukaev, S. Ishimoto, I. Ivanchin, O. Ivanov, T. Iwata, R. Jahn, A. Janata, R. Joosten, N.I. Jouravlev, E. Kabuß, V. Kalinnikov, D. Kang, F. Karstens, W. Kastaun, B. Ketzer, G.V. Khaustov, Yu.A. Khokhlov, J. Kiefer, Yu. Kisselev, F. Klein, K. Klimaszewski, S. Koblitz, J.H. Koivuniemi, V.N. Kolosov, E.V. Komissarov, K. Kondo, K. Königsmann, A.K. Konoplyannikov, I. Konorov, V.F. Konstantinov, A.S. Korentchenko, A. Korzenev, A.M. Kotzinian, N.A. Koutchinski, O. Kouznetsov, K. Kowalik, D. Kramer, N.P. Kravchuk, G.V. Krivokhizhin, Z.V. Kroumchtein, J. Kubart, R. Kuhn, V. Kukhtin, F. Kunne, K. Kurek, N.A. Kuzmin, M. Lamanna, J.M. Le Goff, M. Leberig, A.A. Lednev, A. Lehmann, V. Levinski, S. Levorato, V. I Lyashenko, J. Lichtenstadt, T. Liska, I. Ludwig, A. Maggiora, M. Maggiora, A. Magnon, G.K. Mallot, A. Mann, I.V. Manuilov, C. Marchand, J. Marroncle, A. Martin, J. Marzec, L. Masek, F. Massmann, T. Matsuda, D. Matthiä, A.N. Maximov, G. Menon, W. Meyer, A. Mielech, Yu.V. Mikhailov, M.A. Moinester, F. Molinié, F. Mota, A. Mutter, T. Nagel, O. Nähle, J. Nassalski, S. Neliba, F. Nerling, D. Neyret, M. Niebuhr, T. Niinikoski, V.I. Nikolaenko, A.A. Nozdrin, A.G. Olshevsky, M. Ostrick, A. Padee, P. Pagano, S. Panebianco, B. Parsamyan, D. Panzieri, S. Paul, B. Pawlukiewicz, H. Pereira, D.V. Peshekhonov, V.D. Peshekhonov, D. Piedigrossi, G. Piragino, S. Platchkov, K. Platzer, J. Pochodzalla, J. Polak, V.A. Polyakov, G. Pontecorvo, A.A. Popov, J. Pretz, S. Procureur, C. Quintans, J.-F. Rajotte, S. Ramos, I. Razaq, P. Rebourgeard, D. Reggiani, G. Reicherz, A. Richter, F. Robinet, E. Rocco, E. Rondio, L. Ropelewski, J.Y. Roussé, A.M. Rozhdestvensky, D. Ryabchikov, A.G. Samartsev, V.D. Samoylenko, A. Sandacz, M. Sans Merce, H. Santos, M.G. Sapozhnikov, F. Sauli, I.A. Savin, P. Schiavon, C. Schill, T. Schmidt, H. Schmitt, L. Schmitt, P. Schönmeier, W. Schroeder, D. Seeharsch, M. Seimetz, D. Setter, A. Shaligin, O.Yu. Shevchenko, A.A. Shishkin, H.-W. Siebert, L. Silva, F. Simon, L. Sinha, A.N. Sissakian, M. Slunecka, G.I. Smirnov, D. Sora, S. Sosio, F. Sozzi, A. Srnka, F. Stinzing, M. Stolarski, V.P. Sugonyaev, M. Sulc, R. Sulej, G. Tarte, N. Takabayashi, V.V. Tchalishev, S. Tessaro, F. Tessarotto, A. Teufel, D. Thers, L.G. Tkatchev, T. Toeda, V.V. Tokmenin, S. Trippel, J. Urban, R. Valbuena, G. Venugopal, M. Virius, N.V. Vlassov, A. Vossen, M. Wagner, R. Webb, E. Weise, Q. Weitzel, U. Wiedner, M. Wiesmann, R. Windmolders, S. Wirth, W. Wiślicki, H. Wollny, A.M. Zanetti, K. Zaremba, M. Zavertyaev, J. Zhao, R. Ziegler, M. Ziembicki, Y.L. Zlobin, A. Zvyagin, Abbon, P, Albrecht, E, ALEXAKHIN V., Yu, Alexandrov, Yu, ALEXEEV G., D, ALEKSEEV M., G, Amoroso, A, Angerer, H, ANOSOV V., A, Badelek, B, Balestra, F, Ball, J, Barth, J, Baum, G, Becker, M, Bedfer, Y, Berglund, P, Bernet, C, Bertini, R, Bettinelli, M, Birsa, R, Bisplinghoff, J, Bordalo, P, Bosteels, M, Bradamante, Franco, Braem, A, Bravar, A, Bressan, Andrea, Brona, G, Burtin, E, BUSSA M., P, BYTCHKOV V., N, Chalifour, M, Chapiro, A, Chiosso, M, Ciliberti, Piero, Cicuttin, A, Colantoni, M, COLAVITA A., A, Costa, S, CRESPO M., L, Cristaudo, P, Dafni, T, D'Hose, N, DALLA TORRE, S, D'Ambrosio, C, Das, S, DASGUPTA S., S, Delagnes, E, DE MASI, R, Deck, P, Dedek, N, Demchenko, D, DENISOV O., Yu, Dhara, L, Diaz, V, Dibiase, N, DINKELBACH A., M, DOLGOPOLOV A., V, Donati, A, DONSKOV S., V, DOROFEEV V., A, Doshita, N, Durand, D, Duic, V, Dünnweber, W, Efremov, A, EVERSHEIM P., D, Eyrich, W, Faessler, M, Falaleev, V, Fauland, P, Ferrero, A, Ferrero, L, Finger, M, FINGER M., Jr, Fischer, H, Franco, C, Franz, J, Fratnik, F, FRIEDRICH J., M, Frolov, V, Fuchs, U, Garfagnini, R, Gatignon, L, Gautheron, F, GAVRICHTCHOUK O., P, Gerassimov, S, Geyer, R, GHELLER J., M, Giganon, A, Giorgi, Marcello, Gobbo, B, Goertz, S, GORIN A., M, Gougnaud, F, Grabmüller, S, GRAJEK O., A, Grasso, A, Grube, B, Grünemaier, A, Guskov, A, Haas, F, Hagemann, R, Hannappel, J, VON HARRACH, D, Hasegawa, T, Heckmann, J, Hedicke, S, HEINSIUS F., H, Hermann, R, Hess, C, Hinterberger, F, VON HODENBERG, M, Horikawa, N, Horikawa, S, Horn, I, Ilgner, C, IOUKAEV A., I, Ishimoto, S, Ivanchin, I, Ivanov, O, Iwata, T, Jahn, R, Janata, A, Joosten, R, JOURAVLEV N., I, Kabuss, E, Kalinnikov, V, Kang, D, Karstens, F, Kastaun, W, Ketzer, B, KHAUSTOV G., V, KHOKHLOV Y. U., A, Kiefer, J, Kisselev, Yu, Klein, F, Klimaszewski, K, Koblitz, S, KOIVUNIEMI J., H, KOLOSOV V., N, KOMISSAROV E., V, Kondo, K, Königsmann, K, KONOPLYANNIKOV A., K, Konorov, I, KONSTANTINOV V., F, KORENTCHENKO A., S, Korzenev, A, KOTZINIAN A., M, KOUTCHINSKI N., A, Kouznetsov, O, Kowalik, K, Kramer, D, KRAVCHUK N., P, KRIVOKHIZHIN G., V, KROUMCHTEIN Z., V, Kubart, J, Kuhn, R, Kukhtin, V, Kunne, F, Kurek, K, KUZMIN N., A, Lamanna, M, LE GOFF J., M, Leberig, M, LEDNEV A., A, Lehmann, A, Levinski, V, Levorato, Stefano, I., LYASHENKO V, Lichtenstadt, J, Liska, T, Ludwig, I, Maggiora, A, Maggiora, M, Magnon, A, MALLOT G., K, Mann, A, MANUILOV I., V, Marchand, C, Marroncle, J, Martin, Anna, Marzec, J, Masek, L, Massmann, F, Matsuda, T, Matthiä, D, MAXIMOV A., N, Menon, G, Meyer, W, Mielech, A, MIKHAILOV Y. U., V, MOINESTER M., A, Molinié, F, Mota, F, Mutter, A, Nagel, T, Nähle, O, Nassalski, J, Neliba, S, Nerling, F, Neyret, D, Niebuhr, M, Niinikoski, T, NIKOLAENKO V., I, NOZDRIN A., A, OLSHEVSKY A., G, Ostrick, M, Padee, A, Pagano, P, Panebianco, S, Parsamyan, B, Panzieri, D, Paul, S, Pawlukiewicz, B, Pereira, H, PESHEKHONOV D., V, PESHEKHONOV V., D, Piedigrossi, D, Piragino, G, Platchkov, S, Platzer, K, Pochodzalla, J, Polak, J, POLYAKOV V., A, Pontecorvo, G, POPOV A., A, Pretz, J, Procureur, S, Quintans, C, RAJOTTE J., F, Ramos, S, Razaq, I, Rebourgeard, P, Reggiani, D, Reicherz, G, Richter, A, Robinet, F, Rocco, E, Rondio, E, Ropelewski, L, ROUSSÉ J., Y, ROZHDESTVENSKY A., M, Ryabchikov, D, SAMARTSEV A., G, SAMOYLENKO V., D, Sandacz, A, SANS MERCE, M, Santos, H, SAPOZHNIKOV M., G, Sauli, F, SAVIN I., A, Schiavon, Paolo, Schill, C, Schmidt, T, Schmitt, H, Schmitt, L, Schönmeier, P, Schroeder, W, Seeharsch, D, Seimetz, M, Setter, D, Shaligin, A, SHEVCHENKO O., Yu, SHISHKIN A., A, SIEBERT H., W, Silva, L, Simon, F, Sinha, L, SISSAKIAN A., N, Slunecka, M, SMIRNOV G., I, Sora, D, Sosio, S, Sozzi, F, Srnka, A, Stinzing, F, Stolarski, M, SUGONYAEV V., P, Sulc, M, Sulej, R, Tarte, G, Takabayashi, N, TCHALISHEV V., V, Tessaro, S, Tessarotto, F, Teufel, A, Thers, D, TKATCHEV L., G, Toeda, T, TOKMENIN V., V, Trippel, S, Urban, J, Valbuena, R, Venugopal, G, Virius, M, VLASSOV N., V, Vossen, A, Wagner, M, Webb, R, Weise, E, Weitzel, Q, Wiedner, U, Wiesmann, M, Windmolders, R, Wirth, S, Wisblicki, W, Wollny, H, ZANETTI A., M, Zaremba, K, Zavertyaev, M, Zhao, J, Ziegler, R, Ziembicki, M, ZLOBIN Y., L, and Zvyagin, A.

Subjects
Nuclear and High Energy Physics, straw tube detector, Physics::Instrumentation and Detectors, Project commissioning, FOS: Physical sciences, fixed-target experiment, RICH detector, hadron structure, High Energy Physics - Experiment, target, MWPC, Nuclear physics, High Energy Physics - Experiment (hep-ex), Compass, Hadron spectroscopy, COMPASS experiment, scintillating fibre detector, Nuclear Experiment, silicon microstrip detectors, Instrumentation, Silicon microstrip detectors, Physics, Large Hadron Collider, Structure function, MicroMegas detector, front-end electronics, DAQ, micromegas detector, drift chamber, Physics::Accelerator Physics, High Energy Physics::Experiment, polarised, GEM detector, calorimetry, Particle Physics - Experiment, polarised DIS
Abstract

The COMPASS experiment makes use of the CERN SPS high-intensitymuon and hadron beams for the investigation of the nucleon spin structure and the spectroscopy of hadrons. One or more outgoing particles are detected in coincidence with the incoming muon or hadron. A large polarized target inside a superconducting solenoid is used for the measurements with the muon beam. Outgoing particles are detected by a two-stage, large angle and large momentum range spectrometer. The setup is built using several types of tracking detectors, according to the expected incident rate, required space resolution and the solid angle to be covered. Particle identification is achieved using a RICH counter and both hadron and electromagnetic calorimeters. The setup has been successfully operated from 2002 onwards using a muon beam. Data with a hadron beam were also collected in 2004. This article describes the main features and performances of the spectrometer in 2004; a short summary of the 2006 upgrade is also given., 84 papes, 74 figures

Published
2007
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41. Spin asymmetry A1d and the spin-dependent structure function g1d of the deuteron at low values of x and Q2

Author

Aram Kotzinian, R. Windmolders, M.G. Sapozhnikov, S. Neliba, L. Schmitt, A. Janata, J. Zhao, E. Burtin, J. Lichtenstadt, R. Geyer, D.V. Peshekhonov, P. Schiavon, V.F. Konstantinov, Q. Weitzel, J. Pretz, L. Ferrero, H. Fischer, A.G. Olshevsky, T. Hasegawa, S. Procureur, R. Ziegler, Yu. Alexandrov, A. Chapiro, M. Fabro, V.F. Obraztsov, M. Maggiora, K. Zaremba, D. Neyret, G.I. Smirnov, Fabrice Gautheron, M. A. Faessler, V.A. Polyakov, R. C. Webb, A. Mielech, S. Ishimoto, Frank Klein, Andres Cicuttin, A. Amoroso, G. Reicherz, J. Marzec, St. Goertz, V.Yu. Alexakhin, A. Korzenev, Colin Bernet, Massimo Lamanna, Yu. Kisselev, A. Sandacz, A. Srnka, R. Sulej, C. Ilgner, S. Platchkov, S. Dalla Torre, V.P. Sugonyaev, N.P. Kravchuk, A. Bravar, M. Ostrick, I. Konorov, M. Stolarski, C. Quintans, Grzegorz Brona, Gerhard K. Mallot, A. Zvyagin, Murray Moinester, S. Ramos, Alessandro Bressan, F. Tessarotto, E. M. Kabuß, A.M. Rozhdestvensky, N. V. Khomutov, A. Gorin, I.A. Savin, T. Matsuda, T. Iwata, Z.V. Kroumchtein, F. Sozzi, D. von Harrach, F. Balestra, Franco Bradamante, F.H. Heinsius, Norihiro Doshita, S. Gerassimov, W. Eyrich, J. Ball, L. G. Tkatchev, V. Falaleev, N. Horikawa, H.-W. Siebert, Yu.V. Mikhailov, S. Koblitz, N. d'Hose, E.V. Komissarov, A. Grasso, Sergey Donskov, S. Paul, V. Diaz Kavka, R. Jahn, A. Magnon, A. N. Sissakian, B. Grube, D. Panzieri, J. Nassalski, O.Yu. Denisov, T. Liška, Yu.A. Khokhlov, I. Ludwig, R. Joosten, K. Kurek, G. D. Alexeev, O.A. Grajek, Miroslav Sulc, F. Hinterberger, C. Marchand, A. Maximov, W. Dünnweber, M. Virius, J.M. Friedrich, V.D. Samoylenko, E. Weise, J. Pochodzalla, M.L. Colantoni, S. Hedicke, O.P. Gavrichtchouk, L. Sinha, J. Marroncle, S.S. Dasgupta, N. Takabayashi, J. Bisplinghoff, A.I. Ioukaev, E. Rondio, K. Kondo, R. De Masi, P. Bordalo, M.P. Bussa, A.A. Shishkin, G.V. Khaustov, Alan D. Martin, J. Heckmann, J. Franz, S. Wirth, Y. Bedfer, J. Hannappel, Paolo Pagano, Vladimir Peshekhonov, J. M. Le Goff, R. Birsa, N.I. Jouravlev, S. Horikawa, P.D. Eversheim, G. Piragino, V. Duic, W. Meyer, Maria Liz Crespo, M.E. Ladygin, A.A. Nozdrin, C. Heß, M. Giorgi, V. Frolov, V.N. Kolosov, F. Stinzing, N.A. Koutchinski, R. Kuhn, D. Kang, K. Königsmann, Christian Schill, A. Padee, O. Nähle, R. Bertini, A.B. Sadovski, R. Hermann, Andrea Ferrero, A. Maggiora, V.A. Dorofeev, L. Dhara, M. Slunecka, B. Badelek, W. Wiślicki, B. Gobbo, A.S. Korentchenko, A.M. Dinkelbach, B. Ketzer, A. Teufel, Oleg V. Ivanov, M. von Hodenberg, F. Kunne, A.A. Popov, N.V. Vlassov, Günter Baum, O.Yu. Shevchenko, V.I. Nikolaenko, R. Garfagnini, M. Finger, V.V. Tchalishev, S. Costa, J.H. Koivuniemi, and S. Panebianco

Subjects
Physics, Nuclear and High Energy Physics, Range (particle radiation), Large Hadron Collider, 010308 nuclear & particles physics, media_common.quotation_subject, Structure function, Zero (complex analysis), 01 natural sciences, Asymmetry, Nuclear physics, Deuterium, 0103 physical sciences, COMPASS experiment, 010306 general physics, Spin-½, media_common
Abstract

We present a precise measurement of the deuteron longitudinal spin asymmetry A 1 d and of the deuteron spin-dependent structure function g 1 d at Q 2 1 ( GeV / c ) 2 and 4 × 10 −5 x 2.5 × 10 −2 based on the data collected by the COMPASS experiment at CERN during the years 2002 and 2003. The statistical precision is tenfold better than that of the previous measurement in this region. The measured A 1 d and g 1 d are found to be consistent with zero in the whole range of x.

Published
2007
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42. Gluon polarization in the nucleon from quasi-real photoproduction of high-pT hadron pairs

Author

R. Sulej, S. Neliba, P. Berglund, B. Grube, M.G. Sapozhnikov, H. Schmitt, A. Maggiora, E. Rondio, M. Varanda, A. Zvyagin, W. Kastaun, Colin Bernet, A. Srnka, I. Konorov, M.P. Bussa, A. Korzenev, E.S. Ageev, F. H. Heinsius, S. Gerassimov, J. M. Le Goff, T. Toeda, Marc Wagner, P.D. Eversheim, A. Mielech, S. Ishimoto, Frank Klein, K. Kondo, K. Zaremba, M. Wiesmann, J. Reymann, A.A. Shishkin, V. Duic, Sergey Donskov, O.P. Gavrichtchouk, S. Platchkov, P. Rebourgeard, Y. Bedfer, N. Dedek, L. Sinha, F. Balestra, S. Paul, R. Ziegler, V.N. Kolosov, V.A. Polyakov, N.P. Kravchuk, A.K. Konoplyannikov, J. Zhao, R. Jahn, A. Gorin, V. Diaz, M. Maggiora, R. Ijaduola, N. Takabayashi, R. De Masi, P. Bordalo, J. Bisplinghoff, Massimo Lamanna, Yu. Kisselev, A. Amoroso, Vladimir Peshekhonov, R. Birsa, E.V. Komissarov, Andres Cicuttin, J. Lichtenstadt, Norihiro Doshita, G. Piragino, N. d'Hose, Yu.A. Khokhlov, A. Maximov, G. Reicherz, Josef Pochodzalla, I. Ludwig, Naoaki Horikawa, M. Ostrick, Aram Kotzinian, R. Windmolders, A.A. Nozdrin, J. Nassalski, M. Giorgi, R. Bertini, Andrea Ferrero, Oleg V. Ivanov, R. Joosten, S. Dalla Torre, A. N. Sissakian, J.M. Friedrich, V.D. Samoylenko, Yu. Alexandrov, P. Fauland, Christian Schill, C. Marchand, M.E. Ladygin, V.F. Obraztsov, M. Finger, E. Weise, L. Ferrero, D. Kang, M.L. Colantoni, K. Königsmann, S. Hedicke, A. Colavita, S. Horikawa, R. C. Webb, A.M. Dinkelbach, K. Platzer, V.N. Bytchkov, A.V. Dolgopolov, S. Procureur, K. Kowalik, A.B. Sadovski, L. Cerini, V.I. Tretyak, J. Pretz, A. Grünemaier, G.V. Krivokhizhin, O.A. Grajek, N.A. Koutchinski, M. von Hodenberg, A. Sandacz, F. Karstens, U. Wiedner, S. S. Dasgupta, G.V. Khaustov, L. Schmitt, A. Grasso, M. Stolarski, J. Franz, L. G. Tkatchev, F. Stinzing, Grzegorz Brona, Miroslav Sulc, D. Thers, Anna Zanetti, A. Janata, Franco Bradamante, Gerhard K. Mallot, J. Ehlers, F. Kunne, V.V. Tchalishev, N.I. Jouravlev, S. Costa, E. Burtin, V.F. Konstantinov, W. Meyer, Maria Liz Crespo, A.I. Ioukaev, F. Sozzi, R. Hermann, E. M. Kabuß, Paolo Pagano, V.P. Sugonyaev, Q. Weitzel, A.A. Popov, S. Ramos, J.H. Koivuniemi, K. Rith, F. Hinterberger, P. Schiavon, S. Panebianco, H. Fischer, K. Medved, Alan D. Martin, Z.V. Kroumchtein, W. Eyrich, T. Hasegawa, A. Chapiro, Murray Moinester, T. Schmidt, D. Neyret, M. A. Faessler, Alessandro Bressan, D. von Harrach, C. Ilgner, Yu.V. Mikhailov, S. Trousov, J. Marzec, R. Geyer, A.G. Olshevsky, St. Goertz, O.Yu. Denisov, C. Heß, A. Magnon, L. Dhara, M. Slunecka, Takahiro Iwata, E. Saller, S. Koblitz, M. Sans, B. Gobbo, B. Badelek, J. Marroncle, A. Teufel, Miroslav Virius, K. Kurek, A. Padee, B. Ketzer, D. Peshekhonov, W. Wiślicki, H. D. Pereira, N.V. Vlassov, S. Wirth, C. Quintans, J. Hannappel, Günter Baum, O.Yu. Shevchenko, I.A. Savin, A. Bravar, V.I. Nikolaenko, R. Garfagnini, H.-W. Siebert, I. Manuilov, V. Falaleev, D. Panzieri, T. Liška, M. Fabro, M. Leberig, A.M. Rozhdestvensky, N. V. Khomutov, J. Ball, G.I. Smirnov, Fabrice Gautheron, T. Matsuda, V. Frolov, V.Yu. Alexakhin, W. Dünnweber, G. D. Alexeev, V.A. Dorofeev, A.S. Korentchenko, F. Tessarotto, R. Kuhn, O. Nähle, V. Kalinnikov, and A. Skachkova

Subjects
Quantum chromodynamics, Physics, Nuclear and High Energy Physics, Particle physics, Muon, 010308 nuclear & particles physics, Hadron, Deep inelastic scattering, 01 natural sciences, Helicity, Gluon, Nuclear physics, 0103 physical sciences, COMPASS experiment, High Energy Physics::Experiment, Nuclear Experiment, 010306 general physics, Nucleon
Abstract

We present a determination of the gluon polarization Δ G / G in the nucleon, based on the helicity asymmetry of quasi-real photoproduction events, Q 2 1 ( GeV / c ) 2 , with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarized muon beam scattered on a polarized 6 LiD target. The helicity asymmetry for the selected events is 〈 A ∥ / D 〉 = 0.002 ± 0.019 ( stat ) ± 0.003 ( syst ) . From this value, we obtain in a leading-order QCD analysis Δ G / G = 0.024 ± 0.089 ( stat ) ± 0.057 ( syst ) at x g = 0.095 and μ 2 ≃ 3 ( GeV / c ) 2 .

Published
2006
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43. The COMPASS trigger system for muon scattering

Author

R. Windmolders, Frank Klein, E. M. Kabuß, M. Leberig, A. Bravar, R. Hermann, J. Hannappel, J. Zhao, A. Korzenev, D. v. Harrach, J. Pretz, C. Bernet, and M. Ostrick

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Large Hadron Collider, Muon, Photon, Physics::Instrumentation and Detectors, Scattering, Deep inelastic scattering, Nuclear physics, Hodoscope, Radiative transfer, COMPASS experiment, High Energy Physics::Experiment, Instrumentation
Abstract

The trigger system of the COMPASS experiment at the CERN polarized muon beam is presented. It detects muon scattering events on (polarized) nucleons with a relative energy loss exceeding a selectable value y min independent of the four-momentum transfer. The requirement of a minimum energy deposit in a hadron calorimeter rejects background events like scattering on electrons, elastic and quasi-elastic radiative events as well as events from beam halo tracks. The trigger system which can be considered as a tagger for quasi-real photon events is now, along with larger trigger hodoscope system for deep inelastic scattering events, in regular use for the measurement of the gluon polarisation Δ G / G .

Published
2005
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44. Measurement of the reaction γp → K0Σat photon energies up to 2.6 GeV⋆

Author

D. Menze, F. W. Wieland, Frank Klein, S. Goers, J. Hannappel, J. Barth, Eberhard Klempt, C. Bennhold, R. Lawall, N. Joepen, M. Ostrick, W. J. Schwille, E. Paul, T. Mart, I. Schulday, K. H. Glander, and C. Wu

Subjects
Physics, Nuclear and High Energy Physics, Range (particle radiation), Photon, Nuclear Theory, Sigma, Electron, Photon energy, Polarization (waves), Nuclear physics, Cross section (physics), Isobar, High Energy Physics::Experiment, Nuclear Experiment
Abstract

The reaction gamma p --> K0 Sigma+ was measured in the photon energy range from threshold up to 2.6 GeV with the SAPHIR detector at the electron stretcher facility, ELSA, in Bonn. Results are presented on the reaction cross section and the polarization of the Sigma+ as a function of the kaon production angle in the centre-of-mass system, cos(Theta_K^{c.m.}), and the photon energy. The cross section is lower and varies less with photon energy and kaon production angle than that of gamma p --> K+ Sigma0. The Sigma+ is polarized predominantly at cos(Theta_K^{c.m.}) \approx 0. The data presented here are more precise than previous ones obtained with SAPHIR and extend the photon energy range to higher values. They are compared to isobar model calculations.

Published
2005
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45. Photoproduction of ρmesons and Δ-baryons in the reaction γp → pπ+π- at energies up to $ \sqrt{{s}}$ = 2.6 GeV

Author

Eberhard Klempt, W. Braun, H. van Pee, C. Wu, F. W. Wieland, Friedrich Klein, J. Barth, Frank Klein, D. Menze, R. Lawall, K. H. Glander, W. Neuerburg, E. Paul, J. Ernst, W. J. Schwille, J. Wißkirchen, I. Schulday, M. Ostrick, H. Kalinowsky, J. Link, N. Jöpen, B. Wiegers, and J. Hannappel

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Photon, Meson, Nuclear Theory, Hadron, Electron, Resonance (particle physics), Helicity, Delta baryon, Nuclear physics, Baryon, High Energy Physics::Experiment, Nuclear Experiment
Abstract

The photoproduction of ρ0-mesons and Δ-baryons at photon energies up to 2.6 GeV has been studied with the SAPHIR detector at the electron stretcher ELSA. Total and differential cross-sections were obtained. The decay angular distributions of ρ0-mesons show that s-channel helicity conservation, which is valid at high photon energies, is broken near threshold. The energy dependencies of the decay angular distributions in the helicity system as well as in the Gottfried-Jackson system hint at small s- or u-channel resonance contributions. For the reactions γp → Δ{++}π- and γp → Δ0π+ new data on cross-sections are presented.

Published
2004
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46. Measurement of $\gamma p \rightarrow K^ + \Lambda$ and $\gamma p \rightarrow K^ + \Sigma^0$ at photon energies up to 2.6 GeV

Author

W. Braun, I. Schulday, N. Jöpen, F. W. Wieland, W. J. Schwille, J. Wißkirchen, C. Wu, K. H. Glander, R. Lawall, H. v. Pee, M. Ostrick, E. Paul, D. Menze, W. Neuerburg, J. Link, J. Hannappel, Eberhard Klempt, J. Barth, and Friedrich Klein

Subjects
Physics, Nuclear physics, Nuclear and High Energy Physics, Photon, Hyperon, High Energy Physics::Experiment, Electron, Photon energy, Nuclear Experiment, Polarization (waves), Lambda, Legendre polynomials, Induced polarization
Abstract

The reactions gamma p --> K+ Lambda and gamma p --> K+ Sigma0 were measured in the energy range from threshold up to a photon energy of 2.6 GeV. The data were taken with the SAPHIR detector at the electron stretcher facility, ELSA. Results on cross sections and hyperon polarizations are presented as a function of kaon production angle and photon energy. The total cross section for Lambda production rises steeply with energy close to threshold, whereas the Sigma0 cross section rises slowly to a maximum at about E_gamma = 1.45 GeV. Cross sections together with their angular decompositions into Legendre polynomials suggest contributions from resonance production for both reactions. In general, the induced polarization of Lambda has negative values in the kaon forward direction and positive values in the backward direction. The magnitude varies with energy. The polarization of Sigma0 follows a similar angular and energy dependence as that of Lambda, but with opposite sign.

Published
2004
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47. Evidence for the positive-strangeness pentaquark Θ+ in photoproduction with the SAPHIR detector at ELSA

Author

F. W. Wieland, W. Braun, J. Link, B. Wiegers, H. van Pee, J. Hannappel, Frank Klein, R. Lawall, J. Ernst, J. Wißkirchen, M. Ostrick, D. Menze, N. Jöpen, Eberhard Klempt, J. Barth, W. Neuerburg, H. Kalinowsky, E. Paul, I. Schulday, K. H. Glander, W. J. Schwille, and C. Wu

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Isoscalar, Electron, Strangeness, Resonance (particle physics), Pentaquark, High Energy Physics - Experiment, Nuclear physics, Baryon, Exotic baryon, Other particles, Invariant mass, Pentaquark with strangeness S=1
Abstract

The positive--strangeness baryon resonance $\Theta^+$ is observed in photoproduction of the $\rm nK^+K^0_s$ final state with the SAPHIR detector at the Bonn ELectron Stretcher Accelerator ELSA. It is seen as a peak in the $\rm nK^+$ invariant mass distribution with a $4.8\sigma$ confidence level. We find a mass $\rm M_{\Theta^+} = 1540\pm 4\pm 2$ MeV and an upper limit of the width $\rm \Gamma_{\Theta^+} < 25$ MeV at 90% c.l. From the absence of a signal in the $\rm pK^+$ invariant mass distribution in $\rm\gamma p\to pK^+K^-$ at the expected strength we conclude that the $\Theta^+$ must be isoscalar., Comment: 9 pages, 4 figures

Published
2003
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48. Low-energy photoproduction of $\omega$ -mesons

Author

J. Barth, I. Schulday, J. Hannappel, W. Braun, E. Paul, F. W. Wieland, R. Lawall, J. Ernst, J. Wißkirchen, W. Neuerburg, B. Wiegers, H. Kalinowsky, W. J. Schwille, C. Wu, M. Ostrick, Frank Klein, J. Link, Eberhard Klempt, Friedrich Klein, N. Jöpen, K. H. Glander, D. Menze, and H. van Pee

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Meson, Nuclear Theory, Hadron, Detector, Electron, Helicity, Omega, Nuclear physics, Nuclear fusion, High Energy Physics::Experiment, Vector meson, Nuclear Experiment
Abstract

The photoproduction of the vector meson $\omega$ has been studied between threshold and W = 2.4 GeV with the SAPHIR detector at the Bonn electron stretcher ring ELSA. Besides, the total cross-sections angular distributions in the CMS and decay angular distributions in the helicity and Gottfried-Jackson systems have been measured.

Published
2003
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49. Low-energy photoproduction of Φ-mesons

Author

D. Menze, J. Hannappel, W. Braun, I. Schulday, B. Wiegers, R. Lawall, K. H. Glander, Eberhard Klempt, Frank Klein, J. Wißkirchen, M. Ostrick, J. Ernst, J. Link, H. van Pee, F. W. Wieland, W. Neuerburg, H. Kalinowsky, J. Barth, N. Jöpen, E. Paul, Friedrich Klein, C. Wu, and W. J. Schwille

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Spectrometer, Meson, Nuclear Theory, Hadron, Electron, Nuclear physics, Angular distribution, Low energy, Nuclear fusion, High Energy Physics::Experiment, Nuclear Experiment
Abstract

Photoproduction of Φ-vector-mesons has been studied from reaction threshold up to W = 2.4 GeV with the SAPHIR spectrometer at the Bonn electron stretcher ring ELSA. Total cross-sections, differential cross-sections and decay angular distributions were measured. We find evidence for strong non-diffractive contributions to Φ photoproduction.

Published
2003
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50. N(1520)3/2−Helicity Amplitudes from an Energy-Independent Multipole Analysis Based on New Polarization Data on Photoproduction of Neutral Pions

Author

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

Subjects
Physics, 010308 nuclear & particles physics, Linear polarization, Partial wave analysis, General Physics and Astronomy, Electron, Polarization (waves), 01 natural sciences, Helicity, Nuclear physics, Amplitude, Pion, 0103 physical sciences, Nuclear Experiment, 010306 general physics, Multipole expansion
Abstract

New data on the polarization observables T, P, and H for the reaction γp→pπ0 are reported. The results are extracted from azimuthal asymmetries when a transversely polarized butanol target and a linearly polarized photon beam are used. The data were taken at the Bonn electron stretcher accelerator ELSA using the CBELSA/TAPS detector. These and earlier data are used to perform a truncated energy-independent partial wave analysis in sliced-energy bins. This energy-independent analysis is compared to the results from energy-dependent partial wave analyses.

Published
2014
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