Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Twist-3 in Proton Nucleon Single Spin Asymmetries   These proceedings contain the 'physical' derivation of the Wandzura-Wilczek
relations for the spin-dependent structure function g2 (amounting to keeping
the intrinsic transverse momentum of quarks, and neglecting the physical
transverse components of the gluon fields), recently generalized for the case
of non-forward processes (hep-ph/0102209). The simple numerical model for the
twist-3 contribution to g2 was also suggested.

1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con