Eur. Phys. J. A 17, 241-244 (2003)
DOI: 10.1140/epja/i2002-10153-2

First measurement of the helicity-dependent differential cross-section

J. Ahrens¹, S. Altieri^{2, 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. Panzeri^{2, 3}, P. Pedroni², T. Pinelli^{2, 3}, I. Preobrajenski^{1, 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. Zeitler<sup>5

1</sup>  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 reaction has been measured for the first time at a center-of-mass angle in the photon energy range from 780 MeV to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4 -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