Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-Photon and Two-gluon Decays of $0^{++}$ and $2^{++}$ P-wave Heavy
  Quarkonium States   By neglecting the relative quark momenta in the propagator term, the
two-photon and two-gluon decay amplitude of heavy quarkonia states can be
written as a local heavy quark field operator matrix element which could be
obtained from other processes or computed with QCD sum rules technique or
lattice simulation, as shown in a recent work on $\eta_{c,b}$ two-photon
decays. In this talk, I would like to discuss a similar calculation on $P$-wave
$\chi_{c0,2}$ and $\chi_{b0,2}$ two-photon decays. We show that the effective
Lagrangian for the two-photon decays of the $P$-wave $\chi_{c0,2}$ and
$\chi_{b0,2}$ is given by the heavy quark energy-momentum tensor local operator
and its trace, the $\bar{Q}Q$ scalar density. A simple expression for
$\chi_{c0}$ two-photon and two-gluon decay rate in terms of the $f_{\chi_{c0}}$
decay constant, similar to that of $\eta_{c}$ is obtained. From the existing
  QCD sum rules value for $f_{\chi_{c0}}$, we get $5\rm\,keV$ for the
$\chi_{c0}$ two-photon width, somewhat larger than measurement.

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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: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
1
The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: math
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The categories of this paper are: mtrl-th
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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: q-alg
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The categories of this paper are: solv-int