Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Single Transverse Spin Asymmetry in $p^\uparrow p \to \pi X$ and
  $ep^\uparrow \to \pi X$   Single transverse spin asymmetry for the pion production in pp and ep
collisions is studied in the framework of collinear factorization. The
soft-gluon pole contributions with twist-3 distribution and fragmentation
functions are identified and its characteristic features are discussed.

37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex