Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Backward spin polarizability $\gamma_\pi$ of the proton   Using the Mainz $48 cm {\O}\times 64 cm$ NaI(Tl) detector and the segmented
G\"ottingen recoil detector SENECA in coincidence, Compton scattering by the
proton at $\theta^{lab}_\gamma = 136^\circ$ has been measured at MAMI (Mainz)
in the energy range from 200 to 470 MeV. The new data confirm the previous
observation that there is a systematic discrepancy between MAMI and LEGS
(Brookhaven) data leading to different spin polarizabilities $\gamma_\pi = -
38.7 \pm 1.8$ and $-27.2 \pm 3.1$ $(\times 10^{-4}fm^4)$, respectively.

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The categories of this paper are: hep-th
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The categories of this paper are: physics
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The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas
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The categories of this paper are: nlin
30
The categories of this paper are: q-alg
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The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: supr-con