Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An Interesting Charmonium State Formation and Decay : $p \bar p \to
  ^1D_2 \to ^1P_1 \gamma$   Massless perturbative QCD forbids, at leading order, the exclusive
annihilation of proton-antiproton into some charmonium states, which, however,
have been observed in the $p\bar p$ channel, indicating the significance of
higher order and non perturbative effects in the few GeV energy region. The
most well known cases are those of the $^1S_0$ ($\eta_c$) and the $^1P_1$. The
case of the $^1D_2$ is considered here and a way of detecting such a state
through its typical angular distribution in the radiative decay $^1D_2 \to$
$^1P_1 \gamma$ is suggested. Estimates of the branching ratio $BR(^1D_2 \to
p\bar p)$, as given by a quark-diquark model of the nucleon, mass corrections
and an instanton induced process are presented.

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The categories of this paper are: dg-ga
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The categories of this paper are: alg-geom
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
30
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: patt-sol
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The categories of this paper are: supr-con
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The categories of this paper are: adap-org