Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photoproduction of eta mesons off protons for photon energies from 0.75
  GeV to 3 GeV   Total and differential cross sections for the reaction p(gamma, eta)p have
been measured for photon energies in the range from 750 MeV to 3 GeV. The
low-energy data are dominated by the S11 wave which has two poles in the energy
region below 2 GeV. Eleven nucleon resonances are observed in their decay into
p eta. At medium energies we find evidence for a new resonance N(2070)D15 with
(mass, width) = (2068+-22, 295+-40) MeV. At photon energies above 1.5 GeV, a
strong peak in forward direction develops, signalling the exchange of vector
mesons in the t channel.

10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph