Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-photon exchange amplitudes for the elastic $ep$ scattering at
  Q^2=2.5 GeV^2 from the experimental data   We extract two-photon exchange amplitudes for the elastic electron-proton
scattering at Q^2=2.5 GeV^2 from the unpolarized cross-section and recent
polarization transfer measurements. There are three independent amplitudes, but
only one of them, \delta G_M, can be determined with a reasonable
accuracy(about 10%). The result is in good agreement with theoretical
predictions. Rough estimates for two other amplitudes are obtained.

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The categories of this paper are: ao-sci
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The categories of this paper are: cond-mat
3
The categories of this paper are: physics
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: gr-qc
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: cs
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The categories of this paper are: chao-dyn