2018 Impact factor 2.481
Hadrons and Nuclei
Eur. Phys. J. A 17, 241-244 (2003)
DOI: 10.1140/epja/i2002-10153-2

First measurement of the helicity-dependent $\mth{\arrowvec{\gamma} \arrowvec{p} \to p \eta}$ differential cross-section

J. Ahrens1, S. Altieri2, 3, J.R.M. Annand4, G. Anton5, H.-J. Arends1, K. Aulenbacher1, R. Beck1, C. Bradtke6, A. Braghieri2, N. d'Hose7, D. Drechsel1, H. Dutz8, S. Goertz6, P. Grabmayr9, K. Hansen10, J. Harmsen6, D. von Harrach1, S. Hasegawa11, T. Hasegawa12, E. Heid1, K. Helbing5, H. Holvoet13, L. Van Hoorebeke13, N. Horikawa14, T. Iwata11, O. Jahn1, P. Jennewein1, T. Kageya14, B. Kiel5, F. Klein8, R. Kondratiev15, K. Kossert16, J. Krimmer9, M. Lang1, B. Lannoy13, R. Leukel1, V. Lisin15, T. Matsuda12, J.C. McGeorge4, A. Meier6, D. Menze8, W. Meyer6, T. Michel5, J. Naumann5, A. Panzeri2, 3, P. Pedroni2, T. Pinelli2, 3, I. Preobrajenski1, 15, E. Radtke6, E. Reichert17, G. Reicherz6, Ch. Rohlof 8, G. Rosner4, D. Ryckbosch13, M. Sauer9, B. Schoch8, M. Schumacher16, B. Seitz16, T. Speckner5, N. Takabayashi11, G. Tamas1, A. Thomas1, R. van de Vyver13, A. Wakai14, W. Weihofen16, F. Wissmann16, F. Zapadtka16 and G. Zeitler5

1  Institut für Kernphysik, Universität Mainz, D-55099 Mainz, Germany
2  INFN, Sezione di Pavia, I-27100 Pavia, Italy
3  Dipartimento di Fisica Nucleare e Teorica, Università di Pavia, I-27100 Pavia, Italy
4  Department of Physics & Astronomy, University of Glasgow, Glasgow G12 8QQ, UK
5  Physikalisches Institut, Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
6  Institut für Experimentalphysik, Ruhr-Universität Bochum, D-44801 Bochum, Germany
7  CEA Saclay, DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette Cedex, France
8  Physikalisches Institut, Universität Bonn, D-53115 Bonn, Germany
9  Physikalisches Institut, Universität Tübingen, D-72076 Tübingen, Germany
10  Department of Physics, University of Lund, Lund, Sweden
11  Department of Physics, Nagoya University, Chikusa-ku, Nagoya, Japan
12  Faculty of Engineering, Miyazaki University, Miyazaki, Japan
13  Subatomaire en Stralingsfysica, Universiteit Gent, B-9000 Gent, Belgium
14  CIRSE, Nagoya University, Chikusa-ku, Nagoya, Japan
15  INR, Academy of Science, Moscow, Russia
16  II. Physikalisches Institut, Universität Göttingen, D-37073 Göttingen, Germany
17  Institut für Physik, Universität Mainz, D-55099 Mainz, Germany

arends@kph.uni-mainz.de

(Received: 19 December 2002 / Published online: 20 May 2003)

Abstract
The helicity dependence of the $\arrowvec{\gamma} \arrowvec{p} \to p \eta$ reaction has been measured for the first time at a center-of-mass angle $\theta_\eta^* =70^\circ$ in the photon energy range from 780 MeV to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4 $\pi$-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.

PACS
13.60.Le - Meson production.
14.20.Gk - Baryon resonances with S=0 .
25.20.Lj - Photoproduction reactions.

© Società Italiana di Fisica, Springer-Verlag 2003