Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-photon transitions of charmonia on the light front   We investigate the two-photon transitions $H_{c\bar c} \to \gamma^*\gamma$ of
the charmonium system in light-front dynamics. The light-front wave functions
were obtained from solving the effective Hamiltonian based on light-front
holography and one-gluon exchange interaction within the basis light-front
quantization approach. We compute the two-photon transition form factors as
well as the two-photon decay widths for S- and P-wave charmonia, $\eta_c$ and
$\chi_{cJ}$ and their excitations. Without introducing any free parameters, our
predictions are in good agreement with the recent experimental measurements by
BaBar and Belle, shedding light on the relativistic nature of charmonium.

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The categories of this paper are: cond-mat
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The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nlin
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: comp-gas
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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: chem-ph
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: hep-ex
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The categories of this paper are: econ
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The categories of this paper are: hep-th
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The categories of this paper are: eess