Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Centrality-dependent direct photon pt spectra in Au+Au collisions at
  RHIC   We calculate the centrality-dependence of transverse momentum ($\pt$) spectra
for direct photons in Au+Au collisions at the RHIC energy, based on a realistic
data-constrained (3+1) dimensional hydrodynamic description of the expanding
hot and dense matter, a reasonable treatment of the propagation of partons and
their energy loss in the fluid, and a systematic study of the main sources of
direct photons. The resultant $\pt$ spectra agree with recent PHENIX data in a
broad $\pt$ range. The competition among the different direct photon sources is
investigated at various centralities. Parton energy loss in the plasma is
considered for photons from fragmentation and jet photon conversion, which
causes about 40% decrease in the total contribution. In the high $\pt$ region,
the observed $R_{AA}$ of photons is centrality independent at the accuracy of
5% based on a realistic treatment of energy loss. We also link the different
behavior of $R_{AA}$ for central and peripheral collisions, in the low $\pt$
region, to the fact that the plasma in central collisions is hotter compared to
peripheral ones.

5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an