Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Second Moment of the Structure Function for Pseudoscalar Mesons in
  QCD Sum Rules   We calculate the values of the second moment $M_2^s$ of the flavor-singlet
structure function $F_2^s$ for the pion and the kaon in QCD sum rules, and
investigate how the results depend on their flavor structure (quark contents).
Our calculations give similar values of $M_2^s$ for these two mesons, because
of cancellation among several non-small factors. We emphasize that decay
constants, meson masses and quark masses play an essential role in the above
cancellation.

13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th