Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Valence quark annihilation effect on charmed meson production in pi N
  collisions   We discuss the hadroproduction of charmed mesons in the framework of the
constituent cascade model taking into account the valence quark annihilation.
It is shown that the small valence quark annihilation process dominates the
leading particle production at large Feynman x and explains the recent
experimental data on the asymmetry between D^0 and D^0 bar at 350 GeV/c.

5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph