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8. 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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9. 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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10. 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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11. 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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12. Data on Is and Ic in γ→p→pπ0π0 reveal cascade decays of N(1900) via N(1520)π

Author

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

Subjects
Physics, QC1-999
Abstract

Photoproduction of two neutral pions off the proton is studied using linearly polarized photons, and the polarization observables Is and Ic are measured for the first time. These two observables are unique to multi-meson final states; they characterize correlations between the linear photon polarization and the direction of outgoing single particles in photoproduction of three-body final states. The Is and Ic distributions suggest that, in the 1.8 to 2.0 GeV mass region, the N(1520)3/2−π intermediate state is reached with reaction dynamics consistent with a dominant JP=3/2+ wave. These data are included in the Bonn–Gatchina (BnGa) partial wave analysis which is based on a large variety of data; the analysis confirms a significant contribution from the reaction chain γp→N(1900)3/2+→N(1520)3/2−π0→pπ0π0. Keywords: Baryon spectroscopy, Double meson photoproduction, Polarization observables

Published
2015
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13. 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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14. 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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15. 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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16. 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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17. 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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18. Design and calculation of the $4\pi$-Continuous-Mode-Target current leads

Author

Stefan Runkel, Marcel Bornstein, H. Dutz, and S. Goertz

Subjects
Cryostat, Materials science, Heat flux, Superconducting wire, Magnet, Direct current, engineering, Mechanics, Superconducting magnet, engineering.material, Joule heating, Magnetic field
Abstract

The new concept of the "$4\pi$-Continuous-Mode-Target" will allow the simultaneous usage of a large angular acceptance detector with a continuously polarised target. For polarising a target the process of Dynamic Nuclear Polarisation (DNP) is used which requires low temperatures and a high homogeneous magnetic field within the target volume. A thin, superconducting magnet as a part of the new horizontal cryostat creates a longitudinal magnetic field of 2.5 T with a field homogeneity of $10^{-4}$. Since the internal superconducting magnet is operated with a high direct current there has to be two current leads for connecting the magnet terminals found in the low temperature region to the power supply located at room temperature. Due to Fourier's Law and joule heating a current lead may imply a large heat load on the magnet and the cryostat. As the magnet is operated near its critical parameters, it is important to reduce the heat flux to the superconducting wire to an absolute minimum. The geometry of the normal conducting part of these current leads has been adapted to the cryostat requirements and has been optimised to minimize the heat load. A FVM calculation has been additonally used to check the fulfillment of the requirements.

Published
2019
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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. 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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21. Photoproduction of $ \eta{^\prime}$ -mesons off the deuteron

Author

S. Lugert, D. Walther, S. Hoeffgen, D. Trnka, I. Jaegle, M. Ostrick, Eberhard Klempt, A. V. Anisovich, Matthew Lang, U. Thoma, Kanzo Nakayama, T. Szczepanek, D. Menze, V. Metag, J. Junkersfeld, Fei Huang, V. Kleber, Wolfgang Hillert, V. Crede, H. Loehner, H. van Pee, Yu. A. Beloglazov, A. V. Sarantsev, T. Mertens, D. V. Novinski, S. Kammer, J. C. S. Bacelar, R. Gregor, R. Castelijns, V. A. Nikonov, M. Kotulla, C. Funke, L. Tiator, R. Ewald, O. Bartholomy, D. Elsner, Lalit Mohan Pant, R. Varma, Friedrich Klein, H. Dutz, Ch. Wendel, B. Krusche, Ch. Schmidt, R. W. Novotny, A. Suele, V. V. Sumachev, J. G. Messchendorp, S. Shende, B. Schoch, A. Fix, H. Kalinowsky, V. Sokhoyan, I. V. Lopatin, H. Schmieden, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, R. Beck, S. Schadmand, Ankhi Roy, E. Gutz, B. Bantes, Frank Frommberger, Frank Klein, and M. Pfeiffer

Subjects
Physics, Nuclear and High Energy Physics, Photon, Proton, Meson, Nuclear Theory, Particle accelerator, law.invention, Nuclear physics, Recoil, Deuterium, law, Neutron, High Energy Physics::Experiment, Nucleon, Nuclear Experiment
Abstract

Quasi-free photoproduction of $ \eta{^\prime}$ -mesons off nucleons bound in the deuteron has been measured with the combined Crystal Barrel - TAPS detector. The experiment was done at a tagged photon beam of the ELSA electron accelerator in Bonn for incident photon energies from the production threshold up to 2.5GeV. The $ \eta{^\prime}$ -mesons have been detected in coincidence with recoil protons and recoil neutrons. The quasi-free proton data are in good agreement with the results for free protons, indicating that nuclear effects have no significant impact. The coincidence with recoil neutrons provides the first data for the $ \gamma$ n $ \rightarrow$ n $ \eta{^\prime}$ reaction. In addition, also first estimates for coherent $ \eta{^\prime}$ -production off the deuteron have been obtained. In agreement with model predictions, the total cross-section for this channel is found to be very small, at most at the level of a few nb. The data are compared to model calculations taking into account contributions from nucleon resonances and t -channel exchanges

Published
2018

22. Photoproduction of η -mesons off nuclei for Eγ ⩽ 2.2 GeV

Author

Lalit Mohan Pant, B. Bantes, M. Pfeiffer, D. Menze, R. Ewald, S. Hoeffgen, Ankhi Roy, Ch. Wendel, V. V. Sumachev, H. Kalinowsky, Matthew Lang, A. Ehmanns, R. Varma, D. Elsner, I. Jaegle, S. Kammer, R. Castelijns, H. Dutz, S. Shende, V. Sokhoyan, S. Lugert, D. Trnka, B. Krusche, R. W. Novotny, Ph. Hoffmeister, K. Essig, J. Langheinrich, T. Szczepanek, A. Suele, O. Bartholomy, S. Schadmand, Ulrich Mosel, R. Gregor, Yu. A. Beloglazov, M. Konrad, R. W. Gothe, Eberhard Klempt, J. C. S. Bacelar, M. Kotulla, C.-H. Weinheimer, B. Schoch, C. Morales, M. Ostrick, I. Fabry, Michael Fuchs, R. Beck, E. Gutz, J. Lotz, V. Metag, V. Crede, Ch. Schmidt, Frank Klein, Friedrich Klein, V. Kleber, H. Schmieden, I. V. Lopatin, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, H. van Pee, D. V. Novinski, J. G. Messchendorp, K. Fornet-Ponse, D. Walther, C. Funke, I. Horn, A. Radkov, T. Mertens, U. Thoma, P. Muehlich, J. Junkersfeld, and H. Loehner

Subjects
Mass number, Physics, Nuclear and High Energy Physics, Meson, Nuclear Theory, Nuclear matter, Resonance (particle physics), Nuclear physics, Pion, Production (computer science), High Energy Physics::Experiment, Absorption (logic), Nucleon, Nuclear Experiment
Abstract

Photoproduction of $\eta$ mesons off $^{12}$C, $^{40}$Ca, $^{93}$Nb, and $^{nat}$Pb nuclei has been measured with a tagged photon beam with energies between 0.6 and 2.2 GeV. The experiment was performed at the Bonn ELSA accelerator with the combined setup of the Crystal Barrel and TAPS calorimeters. It aimed at the in-medium properties of the S$_{11}$(1535) nucleon resonance and the study of the absorption properties of nuclear matter for $\eta$ mesons. Careful consideration was given to contributions from $\eta\pi$ final states and secondary production mechanisms of $\eta$-mesons e.g. from inelastic $\pi N$ reactions of intermediate pions. The analysis of the mass number scaling shows that the nuclear absorption cross section $\sigma_{N\eta}$ for $\eta$ mesons is constant over a wide range of the $\eta$ momentum. The comparison of the excitation functions to data off the deuteron and to calculations in the framework of a BUU-model show no unexplained in-medium modifications of the S$_{11}$(1535)., Comment: Accepted for publication in Eur. Phys. J. A

Published
2018

23. 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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24. 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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25. Data onIsandIcinγ→p→pπ0π0reveal cascade decays ofN(1900)viaN(1520)π

Author

H. Schmieden, D. E. Bayadilov, Mariana Nanova, M. Pfeiffer, Y. Beloglazov, H. Dutz, A. Suele, D. Walther, E. Gutz, D. Piontek, V. Crede, T. Szczepanek, J. C. S. Bacelar, A. V. Sarantsev, I. V. Lopatin, Matthew Lang, Frank Frommberger, Lalit Mohan Pant, M. Fuchs, V. Kleber, R. Gregor, Friedrich Klein, A. Gridnev, V. Metag, M. Kotulla, V. Sokhoyan, A. V. Anisovich, Ch. Schmidt, U. Thoma, A. Thiel, R. Ewald, M. Ostrick, S. Kammer, S. Lugert, J. G. Messchendorp, J. Junkersfeld, T. Mertens, Herbert Löhner, Eberhard Klempt, Ch. Funke, I. Jaegle, D. Trnka, R. Varma, B. Bantes, V. A. Nikonov, I. Horn, R. Beck, R. Castelijns, D. V. Novinski, B. Krusche, H. Kalinowsky, Ankhi Roy, Ch. Wendel, V. V. Sumachev, Wolfgang Hillert, D. Elsner, R. W. Novotny, Ph. Hoffmeister, O. Bartholomy, H. van Pee, S. Shende, Frank Klein, and A. Wilson

Subjects
Baryon, Physics, Nuclear physics, Nuclear and High Energy Physics, Pion, Photon, Linear polarization, Partial wave analysis, Photon polarization, Pi, Dalitz plot
Abstract

Photoproduction of two neutral pions off the proton is studied using linearly polarized photons, and the polarization observables I-s and I-c are measured for the first time. These two observables are unique to multi-meson final states; they characterize correlations between the linear photon polarization and the direction of outgoing single particles in photoproduction of three-body final states. The I-s and I-c distributions suggest that, in the 1.8 to 2.0 GeV mass region, the N(1520) 3/2(-)pi intermediate state is reached with reaction dynamics consistent with a dominant J(P) = 3/2(+) wave. These data are included in the Bonn-Gatchina (BnGa) partial wave analysis which is based on a large variety of data; the analysis confirms a significant contribution from the reaction chain gamma p -> N(1900)3/2(+) -> N(1520)3/2(-)pi(0) -> p pi(0)pi(0). (C) 2015 The Authors. Published by Elsevier B.V.

Published
2015
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26. Polarized Solid State Target

Author

W. Meyer, S. Goertz, and H. Dutz

Subjects
Photon, Large Hadron Collider, 010308 nuclear & particles physics, Computer science, Physics, QC1-999, Polarization observables, Solid-state, Continuous mode, Polarization (waves), 01 natural sciences, Engineering physics, Polarized target, Nuclear physics, 0103 physical sciences, 010306 general physics
Abstract

The polarized solid state target is an indispensable experimental tool to study single and double polarization observables at low intensity particle beams like tagged photons. It was one of the major components of the Crystal-Barrel experiment at ELSA. Besides the operation of the ’CB frozen spin target’ within the experimental program of the Crystal-Barrel collaboration both collaborative groups of the D1 project, the polarized target group of the Ruhr Universitat Bochum and the Bonn polarized target group, have made significant developments in the field of polarized targets within the CRC16. The Bonn polarized target group has focused its work on the development of technically challenging polarized solid target systems towards the so called ’4π continuous mode polarized target’ to operate them in combination with 4π -particle detection systems. In parallel, the Bochum group has developed various highly polarized deuterated target materials and high precision NMR-systems, in the meantime used for polarization experiments at CERN, JLAB and MAMI, too.

Published
2017

27. 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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28. 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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29. 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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32. 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

33. 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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34. 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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35. 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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36. Transparency ratio in γA→η′A′ and the in-medium η′ width

Author

B. Krusche, I. Horn, V. Metag, A. Radkov, S. Lugert, O. Bartholomy, D. Menze, Angels Ramos, Eberhard Klempt, S. Höffgen, K.-T. Brinkmann, T. Szczepanek, Ch. Wendel, I. Jaegle, A. Süle, V. V. Sumachev, J. Junkersfeld, K. Essig, C. Morales, M. Fuchs, H. Dutz, Frank Klein, Yu. A. Beloglazov, A. Ehmanns, E. Gutz, Ch. Funke, M. Konrad, Lalit Mohan Pant, M. Ostrick, H. Kalinowsky, M. Pfeiffer, Friedrich Klein, K. Makonyi, R. Ewald, I. V. Lopatin, T. Mertens, Herbert Löhner, H. van Pee, V. Crede, B. Kopf, D. Trnka, J. Langheinrich, J. G. Messchendorp, D. Elsner, U. Thoma, Ankhi Roy, R. W. Novotny, J. Lotz, D. Walther, Ph. Hoffmeister, B. Schoch, Ch. Schmidt, Eulogi Oset, H. Schmieden, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, I. Fabry, S. Schadmand, R. Gregor, and R. Varma

Subjects
Physics, Nuclear and High Energy Physics, Photon, Proton, Meson, 010308 nuclear & particles physics, Scattering, Nuclear Theory, Niobium, chemistry.chemical_element, Rest frame, 7. Clean energy, 01 natural sciences, Momentum, Nuclear physics, Cross section (physics), chemistry, 0103 physical sciences, High Energy Physics::Experiment, Atomic physics, Nuclear Experiment, 010306 general physics
Abstract

The photoproduction of η ′ -mesons off different nuclei has been measured with the CBELSA/TAPS detector system for incident photon energies between 1500–2200 MeV. The transparency ratio has been deduced and compared to theoretical calculations describing the propagation of η ′ -mesons in nuclei. The comparison indicates a width of the η ′ -meson of the order of Γ = 15 – 25 MeV at ρ = ρ 0 for an average momentum p η ′ = 1050 MeV / c , at which the η ′ -meson is produced in the nuclear rest frame. The inelastic η ′ N cross section is estimated to be 3–10 mb. Parameterizing the photoproduction cross section of η ′ -mesons by σ ( A ) = σ 0 A α , a value of α = 0.84 ± 0.03 has been deduced.

Published
2012
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37. Photoproduction of meson pairs: First measurement of the polarization observable Is

Author

Matthew Lang, T. Mertens, Herbert Löhner, A. Suele, Michael Fuchs, V. Crede, D. Piontek, D. Walther, M. Pfeiffer, I. V. Lopatin, A. Thiel, V. Metag, Ch. Schmidt, H. Dutz, V. Sokhoyan, J. G. Messchendorp, M. Kotulla, J. C. S. Bacelar, Friedrich Klein, R. Beck, I. Jaegle, Winston Roberts, M. Ostrick, R. Gregor, R. Ewald, R. Castelijns, S. Schadmand, Ch. Weinheimer, H. Schmieden, R. Varma, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, D. Trnka, D. Elsner, T. Szczepanek, V. Kleber, R. W. Novotny, Ph. Hoffmeister, S. Kammer, B. Schoch, Ch. Funke, Lalit Mohan Pant, S. Lugert, Wolfgang Hillert, Eberhard Klempt, Ankhi Roy, V. A. Nikonov, D. Menze, I. Horn, A. V. Anisovich, Ch. Wendel, B. Bantes, V. V. Sumachev, Yu. A. Beloglazov, A. V. Sarantsev, H. Kalinowsky, B. Krusche, E. Gutz, D. V. Novinski, S. Shende, U. Thoma, H. van Pee, O. Bartholomy, J. Junkersfeld, Frank Frommberger, and Frank Klein

Subjects
Physics, Nuclear and High Energy Physics, Photon, Meson, Proton, Linear polarization, media_common.quotation_subject, Partial wave analysis, FOS: Physical sciences, Observable, Polarization (waves), Asymmetry, Nuclear physics, High Energy Physics::Experiment, Nuclear Experiment (nucl-ex), Nuclear Experiment, media_common
Abstract

The polarization observable I^s, a feature exclusive to the acoplanar kinematics of multi-meson final states produced via linearly polarized photons, has been measured for the first time. Results for the reaction g p -> p pi0 eta are presented for incoming photon energies between 970 MeV and 1650 MeV along with the beam asymmetry I^c. The comparably large asymmetries demonstrate a high sensitivity of I^s to the dynamics of the reaction. Fits using Bonn-Gatchina partial wave analysis demonstrate that the new polarization observables carry significant information on the contributing partial waves., 11 pages, 6 figures, v2 to appear in Phys. Lett. B

Published
2010
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38. Helicity dependence of the $ \gamma$d $ \rightarrow$ $ \pi$NN reactions in the $ \Delta$ -resonance region

Author

Ch. Rohlof, J. Ahrens, Matthew A Blackston, T. Pinelli, R. Beck, Andy Thomas, J. C. McGeorge, M. Lang, N. d'Hose, Saverio Altieri, O. Jahn, V. Lisin, G. Reicherz, C. Bradtke, D. Protopopescu, R. Kondratiev, Frank Klein, A. Braghieri, W. Meyer, G. Rosner, P. Pedroni, Dirk Ryckbosch, H. Dutz, A. Panzeri, J. R. M. Annand, T. Rostomyan, G. Tamas, H. R. Weller, H. J. Arends, A. Fix, M. Schwamb, E. Heid, and M. Martinez-Fabregate

Subjects
Orientation (vector space), Physics, Nuclear physics, Nuclear reaction, Nuclear and High Energy Physics, Particle physics, Pion, Meson, Hadron, Elementary particle, Nuclear Experiment, Nucleon, Helicity
Abstract

The helicity dependence of the differential cross-section for the $ \gamma$ d $ \rightarrow$ $ \pi$ NN reactions has been measured for the first time in the $ \Delta$ -resonance region. The measurement was performed with the large-acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. The data show that the main reaction mechanisms for the $ \pi^{{\pm}}_{}$ NN channels are the quasi-free N $ \pi$ processes on one bound nucleon with nuclear dynamics playing a minor role. On the contrary, for the $ \pi^{0}_{}$ np channel nuclear mechanisms involving the reabsorption of the photoproduced $ \pi^{0}_{}$ by the np pair have to be taken into account to reproduce the experimental data.

Published
2010
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39. Erratum to: High-statistics study of the reaction $\gamma p\rightarrow p2\pi^{0}$

Author

V. Metag, S. Lugert, Eberhard Klempt, T. Seifen, M. Kotulla, Alastair J. Wilson, Frank Klein, M. Ostrick, D. Walther, S. Kammer, Friedrich Klein, T. Mertens, H. Dutz, V. A. Nikonov, Ch. Funke, Herbert Löhner, J. G. Messchendorp, Lalit Mohan Pant, V. Crede, I. Horn, Frank Frommberger, S. Shende, A. Thiel, Ankhi Roy, Ch. Schmidt, V. Sokhoyan, R. Ewald, B. Krusche, H. Pee, O. Bartholomy, M. Pfeiffer, T. Szczepanek, E. Gutz, B. Bantes, H. Kalinowsky, Michael Fuchs, Yu. A. Beloglazov, D. Piontek, J. C. S. Bacelar, A. V. Sarantsev, B. Metsch, D. Trnka, I. V. Lopatin, Ch. Wendel, Matthew Lang, V. V. Sumachev, A. V. Anisovich, I. Jaegle, V. Kleber, R. Gregor, R. Varma, J. Junkersfeld, D. Elsner, R. W. Novotny, Ph. Hoffmeister, U. Thoma, R. Castelijns, H. Schmieden, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, A. Süle, Wolfgang Hillert, D. Novinsky, and R. Beck

Subjects
Physics, Baryon, Nuclear and High Energy Physics, Meson, Isospin, Partial wave analysis, Bremsstrahlung, Dalitz plot, Photon energy, Atomic physics, Nucleon
Abstract

The photoproduction of 2π$^{0}$ mesons off protons was studied with the Crystal Barrel/TAPS experiment at the electron accelerator ELSA in Bonn. The energy of photons produced in a radiator was tagged in the energy range from 600 MeV to 2.5 GeV. Differential and total cross sections and pπ$^{0}$ π$^{0}$ Dalitz plots are presented. Part of the data was taken with a diamond radiator producing linearly polarized photons, and beam asymmetries were derived. Properties of nucleon and Δ resonances contributing to the pπ$^{0}$ π$^{0}$ final state were determined within the Bonn-Gatchina (BnGa) partial-wave analysis. The data presented here allow us to determine branching ratios of nucleon and Δ resonances for their decays into pπ$^{0}$ π$^{0}$ via several intermediate states. Most prominent are decays proceeding via Δ(1232)π, N(1440)1/2$^{+}$ π, N(1520)3/2$^{−}$ π, N(1680)5/2$^{+}$ π, but also pf$_{0}$(500), pf$_{0}$(980), and pf$_{2}$(1270) contribute to the reaction.

Published
2015
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40. High-statistics study of the reaction γp → p2π0

Author

S. Kammer, Ch. Funke, M. Kotulla, V. Crede, T. Szczepanek, E. Gutz, Alastair J. Wilson, H. Schmieden, Yu. A. Beloglazov, J. C. S. Bacelar, A. V. Sarantsev, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, Frank Frommberger, V. Sokhoyan, V. Metag, H. Kalinowsky, H. Dutz, A. V. Anisovich, J. G. Messchendorp, U. Thoma, O. Bartholomy, Friedrich Klein, V. A. Nikonov, M. Pfeiffer, Lalit Mohan Pant, M. Ostrick, J. Junkersfeld, T. Seifen, I. Horn, S. Lugert, Ch. Schmidt, Ch. Wendel, V. V. Sumachev, Eberhard Klempt, T. Mertens, Frank Klein, Herbert Löhner, Michael Fuchs, A. Thiel, D. Piontek, B. Metsch, Ankhi Roy, I. V. Lopatin, H. van Pee, B. Krusche, S. Shende, B. Bantes, Wolfgang Hillert, D. Elsner, R. W. Novotny, Ph. Hoffmeister, I. Jaegle, D. Walther, R. Ewald, R. Varma, V. Kleber, Matthew Lang, R. Gregor, D. Novinsky, R. Beck, D. Trnka, R. Castelijns, and A. Süle

Subjects
Nuclear physics, Physics, Nuclear and High Energy Physics, Range (particle radiation), Photon, Meson, law, Linear polarization, Partial wave analysis, Particle accelerator, Nucleon, Beam (structure), law.invention
Abstract

The photoproduction of 2$\pi^0$ mesons off protons was studied with the Crystal Barrel/TAPS experiment at the electron accelerator ELSA in Bonn. The energy of photons produced in a radiator was tagged in the energy range from 600\,MeV to 2.5\,GeV. Differential and total cross sections and $p\pi^0\pi^0$ Dalitz plots are presented. Part of the data was taken with a diamond radiator producing linearly polarized photons, and beam asymmetries were derived. Properties of nucleon and $\Delta$ resonances contributing to the $p\pi^0\pi^0$ final state were determined within the BnGa partial wave analysis. The data presented here allow us to determine branching ratios of nucleon and $\Delta$ resonances for their decays into $p\pi^0\pi^0$ via several intermediate states. Most prominent are decays proceeding via $\Delta(1232)\pi$, $N(1440)1/2^+\pi$, $N(1520)3/2^-\pi$, $N(1680)5/2^+\pi$, but also $pf_0(500)$, $pf_0(980)$, and $pf_2(1270)$ contribute to the reaction.

Published
2015
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41. Erratum: Modification of theω-Meson Lifetime in Nuclear Matter [Phys. Rev. Lett.100, 192302 (2008)]

Author

M. Kotulla, A. Ehmanns, I. Jaegle, Ulrich Mosel, Gisela Anton, V. Metag, V. Crede, S. Hoeffgen, I. Fabry, R. W. Gothe, Yu. A. Beloglazov, T. Mertens, J. C. S. Bacelar, M. Konrad, S. Shende, J. G. Messchendorp, D. E. Bayadilov, E. Gutz, H. Dutz, J. Lotz, A. B. Gridnev, Mariana Nanova, J. Hoessl, O. Bartholomy, Michael Fuchs, D. Trnka, J. Langheinrich, R. Gregor, I. V. Lopatin, D. Elsner, R. W. Novotny, Ph. Hoffmeister, R. Castelijns, R. Ewald, K. Essig, S. Schadmand, S. Lugert, Eberhard Klempt, P. Muehlich, J. Junkersfeld, H. Loehner, Fritz Klein, I. Horn, D. Menze, B. Kopf, Ch. Funke, B. Krusche, H. Kalinowsky, R. Bogendoerfer, and Frank Klein

Subjects
Nuclear physics, Physics, Particle physics, Meson production, Meson, General Physics and Astronomy, Nuclear matter, Omega
Published
2015
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42. Three-Body Nature ofN*andΔ*Resonances from Sequential Decay Chains

Author

Frank Klein, V. Sokhoyan, A. Wilson, E. Gutz, M. Pfeiffer, S. Shende, J. Junkersfeld, J. G. Messchendorp, R. Beck, D. V. Novinski, Ch. Schmidt, M. Kotulla, D. Walther, V. A. Nikonov, R. Castelijns, Matthew Lang, Wolfgang Hillert, A. Thiel, A. V. Anisovich, I. Horn, S. Lugert, H. Kalinowsky, Cbelsa, U. Thoma, Eberhard Klempt, B. Bantes, V. Kleber, D. Elsner, Volker Metag, H. van Pee, R. Gregor, R. Varma, T. Mertens, Friedrich Klein, Herbert Löhner, R. W. Novotny, Yu. A. Beloglazov, B. Krusche, A. Roy, A. V. Sarantsev, Ph. Hoffmeister, O. Bartholomy, L. M. Pant, H. Dutz, S. Kammer, Bernard Metsch, Frank Frommberger, D. Piontek, Ch. Wendel, Ch. Funke, I. V. Lopatin, V. V. Sumachev, H. Schmieden, V. Crede, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, A. Süle, I. Jaegle, M. Ostrick, D. Trnka, J. C. S. Bacelar, R. Ewald, T. Szczepanek, and M. Fuchs

Subjects
Physics, Partial wave analysis, Nuclear Theory, General Physics and Astronomy, Dalitz plot, Delta baryon, Particle decay, Pion, Isobar, High Energy Physics::Experiment, Decay chain, Atomic physics, Nuclear Experiment, Nucleon
Abstract

The N pi(0)pi(0) decays of positive-parity N* and Delta* resonances at about 2 GeV are studied at ELSA by photoproduction of two neutral pions off protons. The data reveal clear evidence for several intermediate resonances: Delta(1232), N(1520)3/2(-), and N(1680)5/2(+), with spin parities J(P) = 3/2(+), 3/2(-), and 5/2(+). The partial wave analysis (within the Bonn-Gatchina approach) identifies N(1440)1/2(+) and the N(pi pi)s (wave) (abbreviated as N sigma here) as further isobars and assigns the final states to the formation of nucleon and Delta resonances and to nonresonant contributions. We observe the know Delta(1232)pi decays of Delta(1910)1/2(+), Delta(1920)3/2(+), Delta(1905)5/2(+), Delta(1950)7/2(+), and of the corresponding spin-parity series in the nucleon sector, N(1880)1/2(+), N(1900)3/2(+), N(2000)5/2(+), and N(1990)7/2(+). For the nucleon resonances, these decay modes are reported here for the first time. Further new decay modes proceed via N(1440)1/2(pi)(+), N(1520)3/2(pi)(-) , N(1680)5/2(pi)(+), and N sigma. The latter decay modes are observed in the decay of N* resonances and at most weakly in Delta(*) decays. It is argued that these decay modes provide evidence for a 3-quark nature of N* resonances rather than a quark-diquark structure.

Published
2015
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43. Photoproduction of omega mesons off protons and neutrons

Author

A. Süle, S. Höffgren, O. Bartholomy, M. Kotulla, Ankhi Roy, M. Konrad, Friedrich Klein, M. Ostrick, S. Schadmand, Matthew Lang, H. Dutz, M. Pfeiffer, J. C. S. Bacelar, V. Kleber, S. Shende, J. Junkersfeld, H. Schmieden, D. E. Bayadilov, V. Crede, H. Kalinowsky, R. Ewald, A. B. Gridnev, Mariana Nanova, I. Jaegle, A. V. Anisovich, Ch. Schmidt, T. Szczepanek, D. Menze, H. van Pee, S. Kammer, Frank Klein, R. Varma, F. Dietz, A. Wilson, I. V. Lopatin, T. Mertens, Herbert Löhner, U. Thoma, V. Shklyar, Ch. Wendel, Lalit Mohan Pant, Frank Frommberger, C. Funke, R. Beck, D. Walter, V. V. Sumachev, J. G. Messchendorp, R. W. Gothe, R. Castelijns, R. Gregor, D. Trnka, E. Gutz, V. Metag, B. Bantes, T. Rostomyan, V. A. Nikonov, I. Horn, S. Lugert, Eberhard Klempt, Y. A. Belogazov, D. Elsner, R. W. Novotny, Ph. Hoffmeister, B. Schoch, Wolfgang Hillert, B. Krusche, D. V. Novinski, and Research unit Nuclear & Hadron Physics

Subjects
Nuclear reaction, Physics, TAPS, Nuclear and High Energy Physics, Proton, Meson, Astrophysics::High Energy Astrophysical Phenomena, Hadron, Nuclear Theory, WIDTH, Photon energy, DEUTERON, Nuclear physics, Deuterium, NUCLEAR MEDIUM, Neutron, High Energy Physics::Experiment, PHI-PHOTOPRODUCTION, SPECTROMETER, Atomic physics, Nucleon, Nuclear Experiment, MATTER
Abstract

Omega photoproduction off hydrogen and deuterium has been studied with the tagged photon beam of the ELSA accelerator in Bonn for photon energies up to 2.0 GeV. The omega meson has been identified via the omega -> pi(0) gamma -> gamma gamma gamma decay mode, using the combined setup of the Crystal Barrel/TAPS detector systems. Both inclusive and exclusive analyses have been carried out. Differential and total cross-sections have been derived for omega mesons produced off free protons and off protons and neutrons bound in deuterium. The cross-section for the production off the bound neutron is found to be a factor of a parts per thousand 1.3 larger than the one off the bound proton in the incident beam energy region 1.2 GeV

Published
2015
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44. Measurement of the G asymmetry for the γp↦Nπ channels in the Δ(1232) resonance region

Author

J. R. M. Annand, J. Ahrens, E. Heid, R. Beck, G. Rosner, Naoaki Horikawa, St. Goertz, A. Braghieri, G. Reicherz, R. Van de Vyver, R. Kondratiev, P. Grabmayr, P. Jennewein, Saverio Altieri, J. C. McGeorge, B. Lannoy, J. Krimmer, S. Hasegawa, O. Jahn, A. Panzeri, I. Preobrajenski, H. Dutz, F. Zapadtka, M. Lang, N. d'Hose, Dirk Ryckbosch, L. Van Hoorebeke, W. Meyer, K. Livingston, T. Pinelli, Martin Schumacher, H. J. Arends, B. Seitz, M. Rost, G. Tamas, H. Holvoet, Anthony W. Thomas, Takahiro Iwata, P. Pedroni, T. Rostomyan, and Th. Walcher

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Proton, media_common.quotation_subject, Nuclear Theory, Hadron, Resonance, Observable, Asymmetry, Nuclear physics, Physics::Accelerator Physics, Nuclear fusion, Nuclear Experiment, Nucleon, Microtron, media_common
Abstract

The G asymmetry of the γp↦Nπ reaction has been measured for the first time for Eγ = 340±14 MeV. This observable, for which very scarce published data exist, plays an important role to disentangle the contributions of the various nucleon resonances. The experiment, performed at the Mainz microtron MAMI, used a 4π-detector system, a linearly polarized, tagged photon beam, and a longitudinally polarized proton target.

Published
2005
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45. Intermediate resonance excitation in the γp→pπ0π0 reaction

Author

J. Harmsen, A Thomas, R. Van de Vyver, L. Van Hoorebeke, D von Harrach, A. Panzeri, P. Jennewein, Kurt Hansen, I. Preobrajenski, B Schoch, E. Radtke, T Michel, R. Leukel, F. Wissmann, A Braghieri, F. Zapadtka, M. Lang, T. Hasegawa, H Holvoet, B Seitz, J. Naumann, HJ Arends, N. Takabayashi, T Pinelli, W. Meyer, M. Sauer, S Goertz, C Bradtke, E. Reichert, D Ryckbosch, W. Weihofen, S Hasegawa, F. Klein, J Ahrens, O. Jahn, G. Zeitler, V Lisin, A. Wakai, S Altieri, E. Heid, T. Kageya, N. Degrande, D. Menze, Takahiro Iwata, G. Tamas, Jrm Annand, B Lannoy, P. Grabmayr, B Kiel, H Dutz, A. Meier, T. Speckner, T. Rostomyan, R Kondratiev, G Reicherz, N. d'Hose, P Pedroni, JC McGeorge, Ch. Rohlof, K. Aulenbacher, T. Matsuda, R Beck, K. Kossert, G Rosner, K. Helbing, J. Krimmer, M Schumacher, Gisela Anton, and N Horikawa

Subjects
Physics, Nuclear and High Energy Physics, Photon, Proton, 010308 nuclear & particles physics, Resonance, 01 natural sciences, Helicity, Cross section (geometry), Nuclear physics, Excited state, 0103 physical sciences, Physics::Accelerator Physics, Atomic physics, Nuclear Experiment, 010306 general physics, Nucleon, Spin (physics)
Abstract

The helicity dependence of the total cross section for the (gamma) over right arrow(p) over right arrow -> p pi(0)pi(0) reaction has been measured for the first time at incident photon energies from 400 to 800 MeV. The measurement, performed at the tagged photon beam facility of the MAMI accelerator in Mainz, used the large acceptance detector DAPHNE and a longitudinally polarized frozen-spin target. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, most likely due to the intermediate production of the D-13(1520) resonance. However, the contribution of the antiparallel spin configuration, arising from other reaction mechanisms, is also not negligible. This result gives important new information to resolve the existing model discrepancies in the identification of the nucleon resonances contributing to this channel.

Published
2005
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46. VECTOR MESON PRODUCTION IN COLLISIONS OF NUCLEONS

Author

G. J. Wagner, P. Michel, Jens-Christoph Georgi, L. Naumann, L. Pizzolotto, H. Dutz, H. Koch, L. Pinna, J. Kreß, H. Freiesleben, Marc Wagner, E. Roderburg, A. Erhardt, A. Schamlott, M. Schulte-Wissermann, W. Ullrich, S. Dshemuchadse, René Jäkel, S. Marcello, P. Gonser, K. Kilian, M. Steinke, A. Ucar, H. P. Morsch, F. Stinzing, K.-Th. Brinkmann, M. Fritsch, W. Schroeder, G. Y. Sun, P. Zupranski, S. Wirth, K. Ehrhardt, L. Karsch, K. Möller, A. Filippi, E. Kuhlmann, W. Meyer, A. Gillitzer, E. Doroshkevich, W. Eyrich, M. Abdel-Bary, T. Sefzick, S. Abdel-Samad, P. Wintz, H. Clement, A. Wilms, H. Mörtel, P. Wüstner, and P. Schönmeier

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Meson, Spectrometer, proton-proton collisions, vector mesons, hadron physics, Nuclear Theory, Astronomy and Astrophysics, vector meson production, reaction mechanism and resonances, Atomic and Molecular Physics, and Optics, Baryon, Nuclear physics, Formalism (philosophy of mathematics), Hadron physics, Vector meson, Nuclear Experiment, Nucleon, Nucleon-nucleon interaction
Abstract

The production of vector mesons in collisions between nucleons is studied in order to address a variety of issues concerning nucleon-nucleon interaction, reaction mechanism and properties of baryons. These studies are summarized with emphasis on the most recent experiments at the Time-of-Flight spectrometer TOF and results obtained at the COoler SYnchrotron COSY in Jülich. While currently the open questions regarding the so-called OZI violation, its relation to the meson exchange picture and the relative importance of contributions to the production mechanism from various channels within this formalism are still unresolved, the present-day experiments hold the potential to clarify the situation greatly. Possible extensions of the experimental program on vector mesons using 4π detection techniques for charged as well as neutral particles, in particular π0, are discussed.

Published
2005
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47. Helicity dependence of the $\gamma p\rightarrow N \pi$ channels and multipole analysis in the $\Delta$ region

Author

J. Harmsen, R. Van de Vyver, T Michel, H Holvoet, Ch. Rohlof, S Hasegawa, P. Jennewein, K. Aulenbacher, B Seitz, D. Menze, T. Kageya, W. Weihofen, A. Panzeri, G. Zeitler, B Kiel, J Ahrens, Jrm Annand, B Lannoy, I. Preobrajenski, F. Zapadtka, M. Lang, Lothar Tiator, P. Grabmayr, C Bradtke, T. Speckner, O. Jahn, G Reicherz, S Goertz, R Kondratiev, V Lisin, T Pinelli, HJ Arends, K. Helbing, T. Hasegawa, D Ryckbosch, N Degrande, E. Radtke, E. Heid, A Braghieri, N. Takabayashi, G. Tamas, J. Naumann, R Beck, K. Kossert, G Rosner, Dieter Drechsel, W. Meyer, F. Klein, JC McGeorge, Kurt Hansen, M Schumacher, B Schoch, D von Harrach, H Dutz, A. Wakai, A. Meier, P Pedroni, Gisela Anton, N Horikawa, M. Sauer, T. Matsuda, L. Van Hoorebeke, N. d'Hose, J. Krimmer, A Thomas, R. Leukel, S Altieri, E. Reichert, Takahiro Iwata, and F. Wissmann

Subjects
Delta, Nuclear physics, Physics, Nuclear and High Energy Physics, Pi, Atomic physics, Photon beam, Multipole expansion, Resonance (particle physics), Microtron, Helicity
Abstract

A high-quality double-polarization data set for the helicity dependence of the total and differential cross-sections for both gammap --> Npi channels in the Delta region has been obtained in the framework of the GDH experiment. The experiment, performed at the Mainz microtron MAMI, used a 4pi detection system, a circularly polarized photon beam, and a longitudinally polarized frozen-spin target. These data are included in the database to perform a multipole analysis to determine the properties of the Delta(1232)-resonance. For the resonant Delta(1232) multipoles we find a very good agreement with previous analyses, while the nonresonant ones show significant deviations.

Published
2004
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48. Depolarization and spin transfer in with a polarized target

Author

W. Oelert, T. Johansson, R. Gehring, W. Meyer, D. W. Hertzog, D. E. Fields, T. D. Jones, R. Bröders, M. Moosburger, J. Harmsen, R. Stotzer, H. Fischer, F. H. Heinsius, H. Dutz, R. Tayloe, K. Kilian, K. Sachs, R. Geyer, S. Wirth, E. Kriegler, B. Schoch, J. Franz, P. Kingsberry, B. Bunker, H. Schmitt, N. Hamann, F. Stinzing, T. Sefzick, B. Bassalleck, B. P. Quinn, A. Meier, K. Paschke, C. A. Meyer, A. Berdoz, G. B. Franklin, M. Plückthun, St. Goertz, Stephan Pomp, C. Bradtke, J. Hauffe, K. Röhrich, H. Dennert, W. Eyrich, J. Lowe, A. Metzger, P. Khaustov, G. Reicherz, and S. Eilerts

Subjects
Physics, Nuclear and High Energy Physics, Antiproton, Spin transfer, Depolarization, Atomic physics, Nuclear Experiment, Polarization (waves), Instrumentation, Polarized target
Abstract

The reaction p p → Λ Λ was examined by LEAR experiment PS185/3 at 1.525 and 1.640 GeV/c. The proton target was transversely polarized in order to measure the depolarization and spin transfer. Theoretical calculations of Dnn, the component of the depolarization normal to the production plane, differ greatly according to whether quark-gluon or meson-exchange models are employed. The measured Dnn and spin transfer Knn appear to be inconsistent with the specific models cited.

Published
2004
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49. Helicity dependence of the γ→p→→nπ+π0 reaction in the second resonance region

Author

T Pinelli, W. Weihofen, N Degrande, O. Jahn, T Michel, I. Preobrajenski, H Holvoet, F. Zapadtka, M. Lang, R Kondratiev, D. Menze, S Hasegawa, Kurt Hansen, R. Van de Vyver, N. Takabayashi, B Schoch, P. Grabmayr, S Altieri, J. Krimmer, Jrm Annand, B Lannoy, F. Klein, J. Naumann, A. Panzeri, C Bradtke, E. Reichert, A Braghieri, T. Rostomyan, A. Wakai, J. Harmsen, C Rovelli, HJ Arends, M. Sauer, R. Leukel, H Dutz, A. Meier, P Pedroni, W. Meyer, G. Tamas, B Seitz, Gisela Anton, N Horikawa, D von Harrach, T. Kageya, J Ahrens, E. Heid, T. Speckner, T. Hasegawa, R Beck, F. Wissmann, K. Kossert, G Rosner, JC McGeorge, S Goertz, E. Radtke, D Ryckbosch, T. Matsuda, L. Van Hoorebeke, B Kiel, G Reicherz, G. Zeitler, P. Jennewein, N. d'Hose, Takahiro Iwata, V Lisin, K. Helbing, A Thomas, Ch. Rohlof, K. Aulenbacher, and M Schumacher

Subjects
Physics, Nuclear and High Energy Physics, Photon, Proton, 010308 nuclear & particles physics, Nuclear Theory, Resonance, 01 natural sciences, Helicity, Cross section (geometry), Nuclear physics, Excited state, 0103 physical sciences, Pi, Physics::Accelerator Physics, Atomic physics, Nuclear Experiment, 010306 general physics, Spin (physics)
Abstract

The helicity dependence of the total cross section for the (γ) over right arrow(p) over right arrownpi(+) pi(0) reaction has been measured for the first time at incident photon energies from 400 to 800 MeV The measurement was performed with the large acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, due to the intermediate production of the D-13 resonance. (C) 2002 Elsevier Science B.V. All rights reserved.

Published
2003
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50. Three-body nature of N(*) and Δ(*) resonances from sequential decay chains

Author

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

Abstract

The Nπ^{0}π^{0} decays of positive-parity N^{*} and Δ^{*} resonances at about 2 GeV are studied at ELSA by photoproduction of two neutral pions off protons. The data reveal clear evidence for several intermediate resonances: Δ(1232), N(1520)3/2^{-}, and N(1680)5/2^{+}, with spin parities J^{P}=3/2^{+}, 3/2^{-}, and 5/2^{+}. The partial wave analysis (within the Bonn-Gatchina approach) identifies N(1440)1/2^{+} and the N(ππ)_{S wave} (abbreviated as Nσ here) as further isobars and assigns the final states to the formation of nucleon and Δ resonances and to nonresonant contributions. We observe the known Δ(1232)π decays of Δ(1910)1/2^{+}, Δ(1920)3/2^{+}, Δ(1905)5/2^{+}, Δ(1950)7/2^{+}, and of the corresponding spin-parity series in the nucleon sector, N(1880)1/2^{+}, N(1900)3/2^{+}, N(2000)5/2^{+}, and N(1990)7/2^{+}. For the nucleon resonances, these decay modes are reported here for the first time. Further new decay modes proceed via N(1440)1/2^{+}π, N(1520)3/2^{-}π, N(1680)5/2^{+}π, and Nσ. The latter decay modes are observed in the decay of N^{*} resonances and at most weakly in Δ^{*} decays. It is argued that these decay modes provide evidence for a 3-quark nature of N^{*} resonances rather than a quark-diquark structure.

Published
2014

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