Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: In-medium dependence and Coulomb effects of the pion production in heavy
  ion collisions   The properties of the high energy pions observed in heavy ion collisions, in
particular in the system Au on Au at 1 GeV/nucleon are investigated. The
reaction dynamics is described within the Quantum Molecular Dynamics (QMD)
approach. It is shown that high energy pions freeze out early and originate
from the hot, compressed matter. $N^*$--resonances are found to give an
important contribution toward the high energy tail of the pion. Further the
role of in-medium effects in the description of charged pion yields and spectra
is investigated using a microscopic potential derived from the Brueckner
G-matrix which is obtained with the Reid soft-core potential. It is seen that
the high energy part of the spectra is relatively more suppressed due to
in-medium effects as compared to the low energy part. A comparision to
experiments further demonstrates that the present calculations describe
reasonably well the neutral (TAPS) and charged (FOPI) pion spectra. The
observed energy dependence of the $\pi^-/\pi^+$ ratio, i.e. deviations from the
isobar model prediction, is due to Coulomb effects and again indicate that high
energy pions probe the hot and dense phase of the reaction. These findings are
confirmed independently by a simple phase space analysis.

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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph
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The categories of this paper are: astro-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
23
The categories of this paper are: solv-int
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The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
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The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph