Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of the Matrix Element for the Decay $\eta^{\prime} \to \eta
  \pi^+\pi^-$   The Dalitz plot of $\eta^{\prime} \to \eta \pi^+ \pi^-$ decay is studied
using $(225.2\pm2.8)\times 10^6$ $\jpsi$ events collected with the BESIII
detector at the BEPCII $e^+e^-$ collider. With the largest sample of
$\eta^{\prime}$ decays to date, the parameters of the Dalitz plot are
determined in a generalized and a linear representation. Also the branching
fraction of $\jpsi \to \gamma \eta^{\prime}$ is determined to be
$(4.84\pm0.03\pm0.24)\times 10^{-3}$, where the first error is statistical and
the second systematic.

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The categories of this paper are: acc-phys
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The categories of this paper are: atom-ph
3
The categories of this paper are: physics
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph
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The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
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The categories of this paper are: alg-geom