Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anomalous pion production induced by nontrivial topological structure of
  QCD vacuum   A new mechanism for the pion production in the high energy reactions is
suggested. It is related to the possibility for direct production of the pions
induced by instantons, topologically nontrivial gluonic excitations of QCD
vacuum. This mechanism does not require any fragmentation functions for
production of pseudoscalar mesons in high energy reactions with hadrons. We
calculate the contribution of a new mechanism to the inclusive $\pi^0$-meson
production in high energy proton-proton collision. It is shown that it gives
the dominated contribution to the inclusive cross-sections in the few GeV
region for the transverse momentum of final pion. We discuss the possible
application of a new mechanism to the phenomenon of the large spin effects
observed in the numerous high energy reactions.

2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs