2018 Impact factor 2.481
Hadrons and Nuclei


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

Threshold enhancement in $\mth{\eta}$ photoproduction from $\chem{^2H}$ and $\chem{^4He}$

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 2

1  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 $\eta$-mesons from 2H and $^4\mbox{He}$ 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 $\eta$-mesons were detected via their two photon decays with the electromagnetic calorimeter TAPS. Total cross-sections, angular and momentum distributions of the $\eta$-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- $\eta$ final-state interaction effects on different levels of sophistication.

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

© Società Italiana di Fisica, Springer-Verlag 2002