Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Charged pion production in $\mathbf{Au+Au}$ collisions at
  $\mathbf{\sqrt{s_{NN}}}$ = 2.4$\mathbf{GeV}$   We present high-statistic data on charged pion emission from Au+Au collisions
at $\sqrt{s_{\rm{NN}}}$ = 2.4 GeV (corresponding to $E_{beam}$ = 1.23 A GeV) in
four centrality classes in the range 0 - 40$\%$ of the most central collisions.
The data are analyzed as a function of transverse momentum, transverse mass,
rapidity, and polar angle. Pion multiplicity per participating nucleon
decreases moderately with increasing centrality. The polar angular
distributions are found to be non-isotropic even for the most central event
class. Our results on pion multiplicity fit well into the general trend of the
world data, but undershoot by $2.5 \sigma$ data from the FOPI experiment
measured at slightly lower beam energy. We compare our data to state-of-the-art
transport model calculations (PHSD, IQMD, PHQMD, GiBUU and SMASH) and find
substantial differences between the measurement and the results of these
calculations.

4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
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The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
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The categories of this paper are: eess
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom