Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Coherent J/$\psi$ photoproduction in ultra-peripheral Pb-Pb collisions
  at $\sqrt{s_{\rm NN}}$ = 2.76 TeV   The ALICE collaboration has made the first measurement at the LHC of J/$\psi$
photoproduction in ultra-peripheral Pb-Pb-collisions at $\sqrt{s_{\rm NN}}$ =
2.76 TeV. The J/$\psi$ is identified via its dimuon decay in the forward
rapidity region with the muon spectrometer for events where the hadronic
activity is required to be minimal. The analysis is based on an event sample
corresponding to an integrated luminosity of about 55 $\mu$b$^{-1}$. The cross
section for coherent J/$\psi$ production in the rapidity interval $-3.6 < y <
-2.6$ is measured to be d$\sigma$/d$y = 1.00 \pm 0.18$ (stat) $+0.24/-0.26$
(syst) mb. The result is compared to theoretical models for coherent J/$\psi$
production and found to be in good agreement with models which include nuclear
gluon shadowing.

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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: mtrl-th
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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: gr-qc
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The categories of this paper are: math
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The categories of this paper are: stat
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The categories of this paper are: astro-ph
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The categories of this paper are: q-fin
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The categories of this paper are: cs
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: hep-th