Measurement of the beam asymmetry in eta photoproduction off the proton

D. Elsner, A. V. Anisovich, G. Anton, J. C. S. Bacelar, B. Bantes, O. Bartholomy, D. E. Bayadilov, R. Beck, Y. A. Beloglazov, R. Bogendoerfer, R. Castelijns, V. Crede, H. Dutz, A. Ehmanns, K. Essig, R. Ewald, I. Fabry, H. Flemming, K. Fornet-Ponse, M. FuchsC. Funke, R. Gothe, R. Gregor, A. B. Gridnev, E. Gutz, S. Hoeffgen, P. Hoffmeister, I. Horn, J. Hoessl, I. Jaegle, J. Junkersfeld, H. Kalinowsky S. Kammer, V. Kleber Frank Klein, Friedrich Klein, E. Klempt, H. Koch, M. Konrad, B. Kopf, M. Kotulla, B. Krusche, M. Lang, J. Langheinrich, H. Löhner, I. V. Lopatin, J. Lotz, S. Lugert H. Matth Ay, D. Menze, T. Mertens, J. G. Messchendorp, V. Metag, C. Morales, M. Nanova, V. A. Nikonov, D. V. Novinski, R. Novotny, M. Ostrick, L. M. Pant, H. Van Pee, M. Pfeiffer, A. K. Radkov, A. V. Sarantsev, S. Schadmand, C. Schmidt*, H. Schmieden, B. Schoch, S. Shende, A. S. Ule, V. V. Sumachev, T. Szczepanek, U. Thoma, D. Trnka, D. Walther, C. Weinheimer, C. Wendel, G. Suft, A. Suele, V. V. Sumachev, T. Szczepanek, U. Thoma, D. Trnka, D. Walther, C. Weinheimer, C. Wendel

*Corresponding author for this work

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Abstract

The beam asymmetry, Sigma, was measured at ELSA in the reaction gamma p -> eta p using linearly polarised tagged photon beams, produced by coherent bremsstrahlung o ff a diamond. The crystal was oriented to provide polarised photons in the energy range E-gamma = 800 to 1400MeV with the maximum polarisation of P-gamma = 49% obtained at 1305MeV. Both dominant decay modes of the eta into two photons and 3 pi(0) were used to extract the beam asymmetry from the azimuthal modulation of the cross- section. The measurements cover the angular range circle minus cm similar or equal to 50-150 degrees. Large asymmetries up to 80% are observed, in agreement with a previous measurement. The eta- MAID model and the Bonn- Gatchina partial wave analysis describe the measurements, but the required partial waves di ff er significantly.

Original languageEnglish
Pages (from-to)147-155
Number of pages9
JournalEuropean Physical Journal A
Volume33
Issue number2
DOIs
Publication statusPublished - Aug-2007

Keywords

  • RELATIVISTIC QUARK-MODEL
  • STRANGE-BARYON SPECTRUM
  • COHERENT BREMSSTRAHLUNG
  • MESON PHOTOPRODUCTION
  • ELECTROPRODUCTION
  • POLARIZATION
  • THRESHOLD
  • FORCES
  • ELSA

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