2019 Impact factor 2.176
Hadrons and Nuclei
Eur. Phys. J. A 6, 83-89

Near threshold photoproduction of $\eta$ mesons from 4He

V. Hejny1 - P. Achenbach1 - J. Ahrens2 - R. Beck2 - S.J. Hall4 - M. Kotulla1 - B. Krusche1 - V. Kuhr3 - R. Leukel2 - V. Metag1 - R. Novotny1 - V. Olmos de León2 - R.O. Owens4 - F. Rambo3 - A. Schmidt2 - M. Schumacher3 - U. Siodlaczek5 - H. Ströher$^{1,\rm a}$ F. Wissmann3 - J. Weiß1 - M. Wolf1

1 II. Physikalisches Institut, Universität Gießen, D-35392 Gießen, Germany
2 Institut für Kernphysik, Universität Mainz, D-55099 Mainz, Germany
3 II. Physikalisches Institut, Universität Göttingen, D-37073 Göttingen, Germany
4 Department of Physics and Astronomy, University of Glasgow, Glasgow G128QQ, UK
5 Physikalisches Institut, Universität Tübingen, D-72076 Tübingen, Germany

Received: 24 March 1999 / Revised version: 28 June 1999 Communicated by Th. Walcher

Photoproduction of $\eta$ mesons from 4He has been measured for the first time. The experiment was performed at the Mainz Microtron (MAMI) using the TAPS photon spectrometer and the Glasgow/Mainz tagged photon facility. $\eta$ mesons were identified in coincidence with recoil nucleons. Total and differential cross sections are presented in the photon energy range between threshold and 818 MeV. The exclusive data are used to determine the ratio of the elementary production cross sections on bound neutrons and protons, $\sigma_n/\sigma_p=0.68 \pm 0.02 \pm 0.09$. In addition, upper limits for the total coherent cross section have been derived.

13.60.Le Meson production - 14.20.Gk Baryon resonances with S=0 - 14.40.Aq $\pi$,K and $\eta$ mesons - 25.20.Lj Photoproduction reactions - 27.10.+h A$\leq$5

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