First measurement of the helicity-dependent  γ
p?pη differential cross-section |
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| Institution: | (1) Institut für Experimentalphysik, Ruhr-Universit?t Bochum, D-44801 Bochum, Germany, DE;(2) Physikalisches Institut, Universit?t Bonn, D-53115 Bonn, Germany, DE;(3) Physikalisches Institut, Universit?t Erlangen-Nürnberg, D-91058 Erlangen, Germany, DE;(4) Subatomaire en Stralingsfysica, Universiteit Gent, B-9000 Gent, Belgium, BE;(5) CEA Saclay, DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette Cedex, France, FR;(6) Department of Physics & Astronomy, University of Glasgow, Glasgow G12 8QQ, UK, GB;(7) II. Physikalisches Institut, Universit?t G?ttingen, D-37073 G?ttingen, Germany, DE;(8) Department of Physics, University of Lund, Lund, Sweden, SE;(9) Institut für Kernphysik, Universit?t Mainz, D-55099 Mainz, Germany, DE;(10) Institut für Physik, Universit?t Mainz, D-55099 Mainz, Germany, DE;(11) Faculty of Engineering, Miyazaki University, Miyazaki, Japan, JP;(12) INR, Academy of Science, Moscow, Russia, RU;(13) Department of Physics, Nagoya University, Chikusa-ku, Nagoya, Japan, JP;(14) CIRSE, Nagoya University, Chikusa-ku, Nagoya, Japan, JP;(15) INFN, Sezione di Pavia, I-27100 Pavia, Italy, IT;(16) Dipartimento di Fisica Nucleare e Teorica, Università di Pavia, I-27100 Pavia, Italy, IT;(17) Physikalisches Institut, Universit?t Tübingen, D-72076 Tübingen, Germany, DE |
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| Abstract: | The helicity dependence of the γ
p↦pη reaction has been measured for the first time at a center-of-mass angle θ*
η = 70° in the photon energy range from 780 MeV to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4π-detector
system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. The helicity 3/2 cross-section
is found to be small and the results for helicity 1/2 agree with predictions from the MAID analysis.
Received: 19 December 2002 / Accepted: 10 March 2003 / Published online: 20 May 2003 |
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| Keywords: | PACS 13 60 Le Meson production – 14 20 Gk Baryon resonances with S = 0 – 25 20 Lj Photoproduction reactions |
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