Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of a structure at 1.84 GeV/c$^2$ in the $3(\pi^+\pi^-)$ mass
  spectrum in $J/\psi\rightarrow \gamma 3(\pi^+\pi^-)$ decays   With a sample of 225.3 million $J/\psi$ events taken with the BESIII
detector, the decay $J/\psi\rightarrow \gamma 3(\pi^+\pi^-)$ is analyzed. A
structure at 1.84 GeV/c$^2$ is observed in the $3(\pi^+\pi^-)$ invariant mass
spectrum with a statistical significance of 7.6$\sigma$ . The mass and width
are measured to be $M=1842.2\pm 4.2^{+7.1}_{-2.6}$ MeV/c$^2$ and $\Gamma=83\pm
14 \pm 11$ MeV. The product branching fraction is determined to be
$B(J/\psi\rightarrow\gamma X(1840))\times B(X(1840)\rightarrow
3(\pi^+\pi^-))=(2.44\pm0.36^{+0.60}_{-0.74})\times 10^{-5}$. No $\eta^\prime$
signals are observed in the $3(\pi^+\pi^-)$ invariant mass spectrum, and the
upper limit of the branching fraction for the decay $\eta^\prime\rightarrow
3(\pi^+\pi^-)$ is set to be $3.1\times10^{-5}$ at a 90% confidence level.

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The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
16
The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph