Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quasi-free photoproduction of eta-mesons off 3He nuclei   Quasi-free photoproduction of $\eta$-mesons has been measured off nucleons
bound in $^3$He nuclei for incident photon energies from the threshold region
up to 1.4 GeV. The experiment was performed at the tagged photon facility of
the Mainz MAMI accelerator with an almost $4\pi$ covering electromagnetic
calorimeter, combining the TAPS and Crystal Ball detectors. The $\eta$-mesons
were detected in coincidence with the recoil nucleons. This allowed a
comparison of the production cross section off quasi-free protons and
quasi-free neutrons and a full kinematic reconstruction of the final state,
eliminating effects from nuclear Fermi motion. In the $S_{11}$(1535) resonance
peak, the data agree with the neutron/proton cross section ratio extracted from
measurements with deuteron targets. More importantly, the prominent structure
observed in photoproduction off quasi-free neutrons bound in the deuteron is
also clearly observed. Its parameters (width, strength) are consistent with the
expectations from the deuteron results. On an absolute scale the cross sections
for both quasi-free protons and neutrons are suppressed with respect to the
deuteron target pointing to significant nuclear final state interaction
effects.

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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
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The categories of this paper are: eess
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph