Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of $Z_c(3900)^{0}$ in $e^+e^-\to\pi^0\pi^0 J/\psi$   Using a data sample collected with the BESIII detector operating at the
BEPCII storage ring, we observe a new neutral state $Z_c(3900)^{0}$ with a
significance of $10.4\sigma$. The mass and width are measured to be
$3894.8\pm2.3\pm3.2$ MeV/$c^2$ and $29.6\pm8.2\pm8.2$~MeV, respectively, where
the first error is statistical and the second systematic. The Born cross
section for $e^+e^-\to\pi^0\pi^0 J/\psi$ and the fraction of it attributable to
$\pi^0 Z_c(3900)^{0}\to\pi^0\pi^0 J/\psi$ in the range $E_{cm}=4.19-4.42$ GeV
are also determined. We interpret this state as the neutral partner of the
four-quark candidate $Z_c(3900)^\pm$.

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The categories of this paper are: physics
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
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The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
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The categories of this paper are: cs
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The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org