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1. 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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2. 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

3. 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

4. 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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5. 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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6. 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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7. 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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8. 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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9. N∗ and Δ∗ decays into Nπ0π0

Author

D. Menze, Yu. A. Beloglazov, A. V. Sarantsev, Eberhard Klempt, H. Kalinowsky, I. Fabry, V. V. Sumachev, T. Szczepanek, D. Walther, V. A. Nikonov, M. Fuchs, S. Hoeffgen, O. Bartholomy, A. Foesel, A. V. Anisovich, I. Horn, V. Crede, J. Lotz, J. Langheinrich, M. Konrad, H. Flemming, H. van Pee, C. Funke, H. Koch, R. W. Gothe, M. Ostrick, B. Kopf, H. Matthaey, Gisela Anton, U. Thoma, D. V. Novinski, R. Bantes, J. Ernst, Ch. Schmidt, J. Junkersfeld, H. Loehner, B. Krusche, B. Schoch, I. V. Lopatin, H. Schmieden, R. Beck, J. Hoessl, A. B. Gridnev, G. Suft, C.-H. Weinheimer, E. Gutz, A. Ehmanns, and Frank Klein

Subjects
Baryon, Physics, Nuclear and High Energy Physics, Pion, Proton, Hadron spectroscopy, Partial wave analysis, Quark model, Pi, Resonance, High Energy Physics::Experiment, Atomic physics
Abstract

Decays of baryon resonances in the second and the third resonance region into N pi(0)pi(0) are studied by photoproduction of two neutral pions off protons. Partial decay widths of N* and Delta* resonances decaying into Delta(1232)pi, N(pi pi)(S), N(1440)P-11 pi, and N(1520)D-13 pi are determined in a partial wave analysis of this data and of data from other reactions. Several partial decay widths were not known before. Interesting decay patterns are observed which are not even qualitatively reproduced by quark model calculations. In the second resonance region, decays into Delta(1232)pi dominate clearly. The N(pi pi)(S)-wave provides a significant contribution to the cross section, especially in the third resonance region. The P-13(1720) properties found here are at clear variance to PDG values. (c) 2007 Elsevier B.V. All rights reserved.

Published
2008
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10. 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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11. 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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12. 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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13. Quasi-free photoproduction of eta-mesons off the deuteron

Author

D. Walther, U. Thoma, V. Crede, F. Frommberger, D. V. Novinski, S. Schadmand, V. Sokhoyan, V. Metag, S. Lugert, S. Kammer, B. Krusche, L. M. Pant, Yu. A. Beloglazov, Wolfgang Hillert, Eberhard Klempt, J. C. S. Bacelar, R. Castelijns, R. W. Gothe, S. Höffgen, Lilian Witthauer, R. Ewald, Ch. Funke, D. Elsner, O. Bartholomy, R. W. Novotny, Ph. Hoffmeister, H. Kalinowsky, R. Gregor, A. V. Anisovich, Frank Klein, J. Junkersfeld, B. Schoch, E. Gutz, M. Dieterle, T. Mertens, D. Menze, Herbert Löhner, A. V. Sarantsev, H. Schmieden, M. Pfeiffer, D. E. Bayadilov, A. B. Gridnev, Mariana Nanova, A. Roy, D. Trnka, H. van Pee, Ch. Wendel, Friedrich Klein, T. Szczepanek, V. V. Sumachev, V. A. Nikonov, R. Beck, I. Horn, M. Kotulla, B. Bantes, M. Konrad, Matthew Lang, V. Kleber, I. Jaegle, F. Pheron, S. V. Shende, Yasser Maghrbi, H. Dutz, D. Werthmüller, I. Keshelashvili, I. V. Lopatin, J. G. Messchendorp, R. Varma, M. Oberle, A. Süle, Ch. Schmidt, M. Ostrick, KVI - Center for Advanced Radiation Technology, and Research unit Nuclear & Hadron Physics

Subjects
Nuclear reaction, Nuclear and High Energy Physics, Proton, Meson, Hadron, Nuclear Theory, NUCLEON RESONANCE, FOS: Physical sciences, Photon energy, PROTON, ELSA, REGION, Nuclear physics, Effective mass (solid-state physics), Neutron, Nuclear Experiment (nucl-ex), Nuclear Experiment, Physics, NEAR-THRESHOLD PHOTOPRODUCTION, CHIRAL DYNAMICS, EXCLUSIVE MEASUREMENT, POLARIZED PHOTON BEAMS, BARYON RESONANCES, ASYMMETRY, High Energy Physics::Experiment, Nucleon
Abstract

Precise data for quasi-free photoproduction of $\eta$ mesons off the deuteron have been measured at the Bonn ELSA accelerator with the combined Crystal Barrel/TAPS detector for incident photon energies up to 2.5 GeV. The $\eta$-mesons have been detected in coincidence with recoil protons and neutrons. Possible nuclear effects like Fermi motion and re-scattering can be studied via a comparison of the quasi-free reaction off the bound proton to $\eta$-production off the free proton. No significant effects beyond the folding of the free cross section with the momentum distribution of the bound protons have been found. These Fermi motion effects can be removed by an analysis using the invariant mass of the $\eta$-nucleon pairs reconstructed from the final state four-momenta of the particles. The total cross section for quasi-free $\eta$-photoproduction off the neutron reveals even without correction for Fermi motion a pronounced bump-like structure around 1 GeV of incident photon energy, which is not observed for the proton. This structure is even narrower in the invariant mass spectrum of the $\eta$-neutron pairs. Position and width of the peak in the invariant mass spectrum are $W\approx 1665$ MeV and FWHM $\Gamma\approx 25$ MeV. The data are compared to the results of different models., Comment: accepted for publication in Eur. Phys. J. A

Published
2011
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14. Photoproduction of Neutral Pions off Protons

Author

T. Mertens, Herbert Löhner, E. Gutz, V. A. Nikonov, H. Schmieden, Wolfgang Hillert, M. Ostrick, S. Schadmand, Frank Klein, D. E. Bayadilov, Yu. A. Beloglazov, H. Kalinowsky, A. V. Sarantsev, J. C. S. Bacelar, A. Wilson, A. B. Gridnev, D. V. Novinski, H. van Pee, R. Bantes, Mariana Nanova, V. Crede, N. Sparks, V. Sokhoyan, H. Dutz, A. Suele, D. Elsner, Ch. Schmidt, I. Jaegle, Frank Frommberger, R. Varma, R. Castelijns, R. W. Novotny, Ph. Hoffmeister, D. Menze, B. Krusche, R. Gregor, A. V. Anisovich, Friedrich Klein, Volker Metag, S. Shende, S. Kammer, B. Schoch, Ch. Wendel, C. Funke, V. V. Sumachev, M. Pfeiffer, O. Bartholomy, D. Walther, S. Lugert, L. M. Pant, M. Kotulla, Johannes Messchendorp, U. Thoma, Eberhard Klempt, J. Junkersfeld, A. Roy, I. V. Lopatin, R. Beck, R. Ewald, D. Trnka, T. Szczepanek, KVI - Center for Advanced Radiation Technology, and Research unit Nuclear & Hadron Physics

Subjects
Nuclear and High Energy Physics, Particle physics, N(2190), Photon, tagged beam [photon], Meson, 0.85-2.50 GeV, Partial wave analysis, electromagnetic [calorimeter], NUCLEON RESONANCE, FOS: Physical sciences, photoproduction [pi0], +p+pi0%22">photon p --> p pi0, Gamma gamma, REGION, High Energy Physics - Experiment, Nuclear physics, High Energy Physics - Experiment (hep-ex), Pion, High Energy Physics - Phenomenology (hep-ph), Pi, Bonn ELSA Stor, ddc:530, SPECTROMETER, NEAR-THRESHOLD, Nuclear Experiment (nucl-ex), Nuclear Experiment, AMPLITUDES, BARYON, Physics, N(2080), partial wave analysis, OPERATOR EXPANSION METHOD, Baryon, High Energy Physics - Phenomenology, Amplitude, exclusive reaction [photon p], angular dependence [differential cross section], STATES, High Energy Physics::Experiment, CROSS-SECTION, DECAY, small-angle, N(2070), experimental results, +2photon%22">pi0 --> 2photon
Abstract

Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector in the reaction $\gamma p\to p\pi^0$ for photon energies between 0.85 and 2.50 GeV. The $\pi^0$ mesons are observed in their dominant neutral decay mode: $\pi^0\to\gamma\gamma$. For the first time, the differential cross sections cover the very forward region, $\theta_{\rm c.m.}, Comment: 12 pages, 9 figures, minor modifications to PWA section

Published
2011
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15. Measurement of the beam asymmetryΣin the forward direction forγ⃗p→pπ0

Author

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

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Photon, Meson, media_common.quotation_subject, Hadron, Sigma, Elementary particle, Asymmetry, Nuclear physics, Pion, High Energy Physics::Experiment, Nuclear Experiment, Lepton, media_common
Abstract

Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector for photon energies between 0.92 and 1.68 GeV at the electron stretcher accelerator ELSA. The beam asymmetry Sigma has been extracted for 115 degrees > theta(c.m.) > 155 degrees of the pi(0) meson and for theta(c.m.) > 60 degrees. The new beam-asymmetry data cover the very forward region, which extend previously published data for the same reaction by our collaboration and improve the world database for photon energies above 1.5 GeV. The angular dependence of Sigma shows overall good agreement with the SAID parametrization.

Published
2010
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16. Beam asymmetries in near-thresholdωphotoproduction off the proton

Author

V. Sokhoyan, Matthew Lang, M. Pfeiffer, D. Walther, A. Ehmanns, J. Junkersfeld, R. Varma, Ch. Weinheimer, S. Shende, Friedrich Klein, M. Ostrick, H. Kalinowsky, H. Dutz, Frank Klein, A. Roy, R. Beck, D. Elsner, D. Menze, V. Metag, E. Gutz, V. Crede, Ph. Hoffmeister, H. Schmieden, I. Jaegle, D. E. Bayadilov, S. Kammer, A. B. Gridnev, H. van Pee, Mariana Nanova, Ch. Wendel, V. Kleber, Ch. Funke, Yu. A. Beloglazov, R. Castelijns, A. Suele, V. V. Sumachev, A. V. Sarantsev, O. Bartholomy, M. Kotulla, K. Essig, M. Konrad, D. Trnka, R. Novotny, S. Hoeffgen, I. V. Lopatin, T. Mertens, A. V. Anisovich, U. Thoma, Herbert Löhner, B. Bantes, C. Morales, B. Schoch, A. Radkov, J. G. Messchendorp, I. Fabry, J. C. S. Bacelar, R. Gregor, R. Ewald, T. Szczepanek, M. Fuchs, V. A. Nikonov, I. Horn, S. Lugert, Eberhard Klempt, Ch. Schmidt, J. Lotz, D. V. Novinski, B. Krusche, L. M. Pant, Research unit Nuclear & Hadron Physics, and Publica

Subjects
TAPS, Physics, Nuclear and High Energy Physics, Photon, Proton, Meson, media_common.quotation_subject, photon, Nuclear Theory, Bremsstrahlung, Resonance, PHOTONS, MESONS, ETA, Omega, Asymmetry, Nuclear physics, Pion, SPECTROMETER, High Energy Physics::Experiment, Atomic physics, Nuclear Experiment, media_common
Abstract

The photoproduction of {omega} mesons off protons has been studied at the Bonn ELSA accelerator from threshold to E{sub {gamma}}=1700 MeV. Linearly polarized beams were produced via coherent bremsstrahlung. Large photon asymmetries in excess of 50% were obtained. For the first time the pion asymmetries associated with the {omega}{yields}{pi}{sup 0}{gamma} decay were measured and found close to zero. The asymmetries indicate s-channel resonance formation on top of t-channel exchange processes.

Published
2008
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17. Evidence for a Parity DoubletΔ(1920)P33andΔ(1940)D33fromγp→pπ0η

Author

R. Castelijns, D. Menze, J. Junkersfeld, J. Ernst, A. Ehmanns, B. Krusche, Sumachev, J. Hossl, M. Konrad, Herbert Löhner, Crede, B. Kopf, A. V. Anisovich, H. Schmieden, E. Gutz, O. Bartholomy, A. B. Gridnev, D. Walther, M. Ostrick, Metag, J. Lotz, D. V. Novinski, R. Bantes, Frank Klein, Gisela Anton, U. Thoma, V. A. Nikonov, R. W. Gothe, C. Funke, H. Flemming, B. Schoch, Yu. A. Beloglazov, A. V. Sarantsev, H. Kalinowsky, G. Suft, I. V. Lopatin, Messchendorp J, I. Horn, Eberhard Klempt, S. Höffgen, H. Matthäy, van Pee H, C.-H. Weinheimer, R. Beck, I. Fabry, Herbert Koch, R. Bogendorfer, T. Szczepanek, M. Fuchs, J. Langheinrich, A. Fosel, and Ch. Schmidt

Subjects
Delta, Quantum chromodynamics, Physics, Nuclear physics, Particle physics, Total angular momentum quantum number, Partial wave analysis, Quark model, Pi, General Physics and Astronomy, Parity (physics), Nuclear Experiment, Delta baryon
Abstract

Evidence is reported for the existence of a parity doublet of Delta resonances with total angular momentum J=3/2 from photoproduction of the p pi(0)eta final state. The two parity partners Delta(1920)P-33 and Delta(1940)D-33 make significant contributions to the reaction. Cascades of resonances into Delta(1232)eta, N(1535)pi, and Na-0(980) are clearly observed.

Published
2008
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18. Quasifree photoproduction of eta mesons off the neutron

Author

T. Szczepanek, Ch. Weinheimer, B. Schoch, A.B. Gridnev, Herbert Löhner, C. Morales, A. Radkov, V. Metag, U. Thoma, M. Kotulla, D. V. Novinski, H. Dutz, T. Mertens, L.M. Pant, R. Varma, J. Junkersfeld, M. Ostrick, H. van Pee, V. A. Nikonov, R. Ewald, I. Fabry, M. Fuchs, D. Menze, A. Roy, O. Bartholomy, A. Ehmanns, M. Nanova, I. Horn, R. Beck, D. Elsner, J. Lotz, M. Konrad, B. Krusche, V. Sokhoyan, S. Schadmand, Frank Klein, D. Trnka, Eberhard Klempt, Ph. Hoffmeister, Ch. Funke, A. V. Sarantsev, S. Höffgen, R. Gregor, J. Langheinrich, J. C. S. Bacelar, Ch. Wendel, H. Schmieden, D. E. Bayadilov, S. Kammer, S. Lugert, B. Bantes, R. Novotny, K. Essig, M. Pfeiffer, Y.A. Beloglazov, A. Süle, H. Kalinowsky, A.V. Anisovich, R. W. Gothe, Ch. Schmidt, D. Walther, E. Gutz, V. V. Sumachev, Friedrich Klein, I. Jaegle, V. Kleber, S.V. Shende, R. Castelijns, M. Lang, J. G. Messchendorp, V. Crede, I. V. Lopatin, Publica, and KVI - Center for Advanced Radiation Technology

Subjects
Physics, Photon, Meson, Proton, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, NEAR-THRESHOLD PHOTOPRODUCTION, BEAM ASYMMETRY, General Physics and Astronomy, EXCLUSIVE MEASUREMENT, Photon energy, RESONANCE, PROTON, ELSA, DEUTERON, Nuclear physics, Recoil, Deuterium, S-11(1535), High Energy Physics::Experiment, Invariant mass, Neutron, SPECTROMETER, Nuclear Experiment, HE-4
Abstract

Precise data for quasi-free photoproduction of η-mesons off the deuteron have been measured at the Bonn ELSA accelerator with the combined Crystal Barrel/TAPS detector for incident photon energies up to 2.5GeV. The η-mesons have been detected in coincidence with recoil protons and neutrons. Possible nuclear effects like Fermi motion and re-scattering can be studied via a comparison of the quasi-free reaction off the bound proton to η-production off the free proton. No significant effects beyond the folding of the free cross-section with the momentum distribution of the bound protons have been found. These Fermi motion effects can be removed by an analysis using the invariant mass of the η-nucleon pairs reconstructed from the final-state four-momenta of the particles. The total cross-section for quasi-free η-photoproduction off the neutron reveals even without correction for Fermi motion a pronounced bump-like structure around 1GeV of incident photon energy, which is not observed for the proton. This structure is even narrower in the invariant-mass spectrum of the η-neutron pairs. Position and width of the peak in the invariant-mass spectrum are W ≈ 1665 MeV and FWHM Γ ≈ 25 MeV. The data are compared to the results of different models.

Published
2008

19. Photoproduction of eta-mesons off protons

Author

R. W. Gothe, J. Langheinrich, I. Fabry, H. Matthaey, J. Hoebl, Herbert Koch, D. Menze, A. Ehmanns, H. Flemming, R. Bantes, J. Lotz, U. Thoma, H. van Pee, Friedrich Klein, E. Gutz, B. Kopf, V. V. Sumachev, R. Castelijns, J. Junkersfeld, B. Schoch, O. Bartholomy, T. Szczepanek, H. Kalinowsky, H. Loehner, Ch. Funke, D. V. Novinski, V. A. Nikonov, R. Bogendoerfer, J. G. Messchendorp, Gisela Anton, M. Fuchs, I. Horn, A. Radkov, A. V. Sarantsev, J. Ernst, Eberhard Klempt, I. V. Lopatin, V. Crede, B. Krusche, G. Suft, Ch. Weinheimer, M. Konrad, Yu. A. Beloglazov, A. Foesel, M. Ostrick, S. Hoeffgen, A. V. Anisovich, H. Schmieden, A. B. Gridnev, S. Schadmand, Ch. Schmidt, D. Walther, Publica, and KVI - Center for Advanced Radiation Technology

Subjects
Physics, POSITIVE PION-PHOTOPRODUCTION, Nuclear and High Energy Physics, Range (particle radiation), POLARIZATION, Photon, Meson, Partial wave analysis, Hadron, Polarization (waves), SIGMA-BEAM ASYMMETRY, DECAYS, DIFFERENTIAL CROSS-SECTIONS, Nuclear physics, Angular distribution, RELATIVISTIC QUARK-MODEL, PHOTON ENERGIES, STRANGE-BARYON SPECTRUM, Nuclear fusion, High Energy Physics::Experiment, GAMMA-P, Atomic physics, Nuclear Experiment, RESONANCES
Abstract

Photoproduction of η -mesons was studied with the Crystal-Barrel detector at ELSA for photon energies in the range from 0.75 to 3GeV. Total and differential cross-sections are presented. The η mesons are detected in two decay modes, in η → 2γ and in η → 3π0 → 6γ . The cross-sections vary slowly as functions of energy and η production angle suggesting that only few resonances make significant contributions to the cross-section. For photon energies above 1.5GeV, the differential cross-sections show a strong forward peak due to meson exchanges in the t channel. A comparison of the η -photoproduction cross-sections with SAID and MAID as well as with a partial-wave analysis performed on our data in combination with other data sets shows good agreement. The Bonn-Gatchina partial-wave analysis suggests that the largest contribution to η photoproduction for energies below 3GeV proceeds via three resonances, the well-known N(1535)S 11 , via N(1720)P 13 , and a newly suggested N(2070)D 15 .

Published
2007

20. New results on the Roper resonance and the P_{11} partial wave

Author

A. Ehmanns, D. P. Watts, Yu. A. Beloglazov, R. Castelijns, Eberhard Klempt, S. Höffgen, V. A. Nikonov, C. Funke, S. Janssen, I. Horn, V. Metag, D. V. Novinski, D. Walther, A. V. Sarantsev, J. Hößl, I. Fabry, J. R. M. Annand, Herbert Koch, Gisela Anton, U. Thoma, A. V. Anisovich, H. van Pee, R. W. Gothe, J. Ahrens, Herbert Löhner, B. Krusche, M. Pfeiffer, E. Gutz, J. G. Messchendorp, R. Beck, M. Rost, M. Kotulla, A. Radkov, H. Matthäy, D. Menze, H. Flemming, J. C. McGeorge, A. B. Gridnev, M. Konrad, J. Junkersfeld, Frank Klein, C.-H. Weinheimer, I. V. Lopatin, J. Ernst, G. Suft, B. Kopf, O. Bartholomy, I. J. D. MacGregor, D. Hornidge, J. Lotz, A. Fosel, Ch. Schmidt, V. V. Sumachev, G. Rosner, R. Bantes, H. Kalinowsky, V. Crede, M. Ostrick, R. W. Novotny, B. Schoch, J. Langheinrich, T. Szczepanek, M. Fuchs, and KVI - Center for Advanced Radiation Technology

Subjects
TAPS, Nuclear and High Energy Physics, Roper resonance, Photon, Proton, PHOTON SPECTROMETER, Partial wave analysis, Nuclear Theory, Dalitz plot, FOS: Physical sciences, PION-PHOTOPRODUCTION, PROTON, THRESHOLD, Nuclear physics, Pion, High Energy Physics - Phenomenology (hep-ph), Nuclear Experiment, Physics, PI(0) PHOTOPRODUCTION, High Energy Physics - Phenomenology, RELATIVISTIC QUARK-MODEL, STRANGE-BARYON SPECTRUM, POSITIVE-STRANGENESS, FORCES, Nucleon, Excitation
Abstract

Properties of the Roper resonance, the first scalar excitation of the nucleon, are determined. Pole positions and residues of the $P_{11}$ partial wave are studied in a combined analysis of pion- and photo-induced reactions. We find the Roper pole at $\{(1371\pm7)-i(92\pm10)\}$ MeV and an elasticity of $0.61\pm 0.03$. The largest decay coupling is found for the $N\sigma$ ($\sigma=(\pi\pi)$-$S$-wave). The analysis is based on new data on $\gamma p\to p\pi^0\pi^0$ for photons in the energy range from the two-pion threshold to 820 MeV from TAPS at Mainz and from 0.4 to 1.3 GeV from Crystal Barrel at Bonn and includes further data from other experiments. The partial wave analysis excludes the possibility that the Roper resonance is split into two states with different partial decay widths., Comment: 14 pages, 6 figures

Published
2007
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21. Neutral-PionPhotoproduction off Protons in the Energy Range0.3 GeV<Eγ<3 GeV

Author

H. van Pee, M. Konrad, R. Bantes, Gisela Anton, H. Flemming, R. Joosten, M. Ostrick, Herbert Löhner, J. Langheinrich, D. V. Novinski, H. Kalinowsky, Ch. Weinheimer, G. Suft, R. Castelijns, E. Gutz, T. Szczepanek, J. Hossl, R. W. Gothe, A. Radkov, Yu. A. Beloglazov, D. Menze, A. Ehmanns, A. V. Sarantsev, V. Crede, H. Matthäy, B. Krusche, J. Reinnarth, J. Ernst, S. Schadmand, H. Freiesleben, B. Schoch, Frank Klein, C. Morales, A. V. Anisovich, V. V. Sumachev, U. Thoma, R. Bogendorfer, Michael Fuchs, J. Lotz, I. V. Lopatin, H. Schmieden, J. Junkersfeld, J. G. Messchendorp, A. B. Gridnev, D. Walther, I. Fabry, B. Kopf, Herbert Koch, A. Fosel, Ch. Schmidt, Ch. Funke, O. Bartholomy, I. Horn, Eberhard Klempt, and S. Höffgen

Subjects
Nuclear physics, Physics, Range (particle radiation), Particle physics, Pion, Photon, Proton, Partial wave analysis, Solid angle, General Physics and Astronomy, Resonance, Intermediate state
Abstract

Single pi(0) photoproduction has been studied with the CB-ELSA experiment at Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental setup covers a very large solid angle of similar to98% of 4pi. Differential cross sections dsigma/dOmega have been measured. Complicated structures in the angular distributions indicate a variety of different resonances being produced in the s channel intermediate state gammap-->N(*)(Delta(*))-->ppi(0). A combined analysis including the data presented in this letter along with other data sets reveals contributions from known resonances and evidence for a new resonance N(2070)D(15).

Published
2005
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22. PhotoproductionofηMesonsoff Protons for0.75 GeV<Eγ<3 GeV

Author

H. Flemming, M. Konrad, V. Crede, Gisela Anton, B. Kopf, D. V. Novinski, C. Morales, D. Walther, H. van Pee, U. Thoma, H. Schmieden, Ch. Funke, A. B. Gridnev, H. Kalinowsky, A. V. Anisovich, J. Junkersfeld, R. Castelijns, D. Menze, R. Joosten, A. Fosel, Ch. Schmidt, J. Langheinrich, E. Gutz, R. Bantes, S. Schadmand, A. Radkov, O. Bartholomy, M. Ostrick, A. Ehmanns, H. Matthäy, I. Fabry, Herbert Koch, J. G. Messchendorp, Frank Klein, V. V. Sumachev, Yu. A. Beloglazov, A. V. Sarantsev, J. Hosl, B. Krusche, J. Reinnarth, B. Schoch, Michael Fuchs, R. Bogendorfer, T. Szczepanek, Herbert Löhner, I. V. Lopatin, G. Suft, Ch. Weinheimer, I. Horn, Eberhard Klempt, S. Höffgen, J. Ernst, H. Freiesleben, J. Lotz, and R. W. Gothe

Subjects
Physics, Particle physics, Range (particle radiation), Photon, Meson production, Proton, Meson, Astrophysics::High Energy Astrophysical Phenomena, General Physics and Astronomy, Resonance, Nuclear physics, Angular distribution, High Energy Physics::Experiment, Nuclear Experiment, Nucleon
Abstract

Total and differential cross sections for the reaction p(gamma,eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S-11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into peta. At medium energies we find evidence for a new resonance N(2070)D-15 with (M,Gamma)=(2068+/-22, 295+/-40) MeV. At gamma energies above 1.5 GeV, a strong peak in the forward direction develops, signaling the exchange of vector mesons in the t channel.

Published
2005
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