Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Leading-Color Two-Loop QCD Corrections for Three-Photon Production at
  Hadron Colliders
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga