Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Direct Photon Production in Heavy Ion Reactions at SPS and RHIC   A review on experimental results for direct photon production in heavy ion
reactions is given. A brief survey of early direct photon limits from SPS
experiments is presented. The first measurement of direct photons in heavy ion
reactions from the WA98 collaboration is discussed and compared to theoretical
calculations. An outlook on the perspective of photon measurements at RHIC is
given.

17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph