Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurements of vector meson photoproduction with ALICE in
  ultra-peripheral Pb-Pb collisions at $\bf{\sqrt{s_{\rm NN}} = 5.02}$ TeV   The intense photon fluxes of relativistic nuclei provide a possibility to
study photonuclear and two-photon interactions in ultra-peripheral collisions
(UPC) where the nuclei do not overlap and no strong nuclear interactions occur.
The study of such collisions provides information about the initial state of
nuclei. First ALICE results from the LHC Run 2 are presented for forward
exclusive \jpsi production in UPC, which is sensitive to the gluon distribution
in nuclei. The increased statistics and the higher collision energy allows for
a more detailed study at lower values of Bjorken-$x$. The analysis of the
$\gamma+A \rightarrow \rho^0+A$ process in UPC is a tool to test the so-called
black disk regime, where the target nucleus appears like a black disk and the
total $\rho^0+A$ cross section reaches its limit. ALICE reports new
measurements of \rrho photoproduction cross sections in Pb-Pb UPC at
$\sqrt{s_{\rm NN}}=5.02$ TeV at mid-rapidity, which are compared to
predictions.

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The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
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The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph
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The categories of this paper are: solv-int
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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: quant-ph
1
The categories of this paper are: cs