Eur. Phys. J. A 13, 493-499 (2002)
DOI: 10.1140/epja/iepja1345

Threshold enhancement in photoproduction from and

V. Hejny¹, J. Weiß², P. Achenbach³, J. Ahrens³, J.R.M. Annand⁴, R. Beck³, M. Kotulla², B. Krusche⁵, V. Kuhr⁶, R. Leukel³, I.J.D. MacGregor⁴, V. Metag², R. Novotny², V. Olmos de León³, F. Rambo⁶, A. Schmidt³, M. Schumacher⁶, U. Siodlaczek⁷, H. Ströher¹, F. Wissmann⁶ and M. Wolf <sup>2

1</sup>  Institut für Kernphysik, Forschungszentrum Jülich, D-52425, Jülich, Germany
²  II. Physikalisches Institut, Universität Gießen, D-35392 Gießen, Germany
³  Institut für Kernphysik, Universität Mainz, D-55099 Mainz, Germany
⁴  Department of Physics and Astronomy, University of Glasgow, Glasgow G128QQ, UK
⁵  Department of Physics and Astronomy, University of Basel, Ch-4056 Basel, Switzerland
⁶  II. Physikalisches Institut, Universität Göttingen, D-37073 Göttingen, Germany
⁷  Physikalisches Institut, Universität Tübingen, D-72076 Tübingen, Germany

Bernd.Krusche@unibas.ch

(Received: 23 November 2001 / Revised version: 27 January 2002 Communicated by M. Garçon)

Abstract
The photoproduction of -mesons from ²H and has been studied for energies close to the production thresholds. The experiments were carried out with the tagged photon beam of the Mainz MAMI accelerator. The -mesons were detected via their two photon decays with the electromagnetic calorimeter TAPS. Total cross-sections, angular and momentum distributions of the -mesons have been determined for both reactions. The total cross-sections in the threshold region show a large enhancement over the predictions of a participant-spectator model, indicating significant final-state interaction effects. The results are compared to recent model calculations taking into account nucleon-nucleon and nucleon- final-state interaction effects on different levels of sophistication.

PACS
13.60.Le - Meson production.
14.40.Aq - , K and mesons.
25.20.Lj - Photoproduction reactions.

© Società Italiana di Fisica, Springer-Verlag 2002