Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Polarization Phenomena in Small-Angle Photoproduction of e+e- Pairs and
  the Gerasimov-Drell-Hearn Sum Rule   Photoproduction of $e^+e^-$ pairs at small angles is investigated as a tool
to determine the functions $f_1$ and $f_2$ entering the real-photon forward
Compton scattering amplitude. The method is based on an interference of the
Bethe-Heitler and the virtual Compton scattering mechanisms, generating an
azimuthal asymmetry in the $e^+$ versus $e^-$ yield. The general case of a
circularly polarized beam and a longitudinally polarized target allows one to
determine both the real and imaginary parts of $f_1$ as well as $f_2$. The
imaginary part of $f_2$ requires target polarization only. We calculate cross
sections and asymmetries of the reaction $p(\gamma,e^+e^-)p$, estimate
corrections and backgrounds, and propose suitable kinematical regions to
perform the experiment. Our investigation shows that photoproduction of
$e^+e^-$-pairs off the proton and light nuclei may serve as a rather sensitive
test of the validity of the Gerasimov-Drell-Hearn sum rule.

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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: math-ph
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The categories of this paper are: adap-org
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The categories of this paper are: q-bio
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The categories of this paper are: physics
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: patt-sol