Bochum 1998 – scientific programme
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HK: Hadronen und Kerne
HK 26: Electromagnetic Probes IV, Electro-, Photoproduction
HK 26.4: Talk
Tuesday, March 17, 1998, 15:00–15:15, B
Photoproduction of η-mesons from light nuclei [1] — •V. Hejny and J. Weiß — II. Physikalisches Institut, Universität Gießen
The η-meson is a very selective probe for the S11(1535)
nucleon resonance. A consistent theoretical description of the
large ηN branching ratio is, however, still missing.
In order to gain new insight, additional experimental results
are urgently needed.
In 1995/96 the reactions γ + d —→ η + X
and γ + 4He —→ η + X have been measured
using the photon spectrometer TAPS at the Mainz Microtron (MAMI).
In order to explore the quasifree η production from bound nucleons
an additional forward wall was built to detect the recoil nucleon.
Using d and 4He targets the quasifree
proton cross section
from a weakly and a strongly bound system can be compared
with the reaction on a free proton. The results of this analysis can be
used to extract the free neutron cross section from the quasifree data.
Together with the measurement of the coherent cross section from
the deuteron the isospin structure of the S11 resonance can be
deduced.
In case of the coherent production from 4He the S11 does not
contribute, which makes this
reaction very sensitive to the much smaller non-S11 contributions.
Consequently, the observed yield is close to the detection limit.
The current status of the analysis will be presented.
[1] supported by BMBF and SFB 201