Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pion Distribution Amplitude and Photon-to-Pion Transition Form Factor in
  QCD   We discuss the status of the pion distribution amplitude (DA) in connection
with QCD sum rules and experimental data on the $\gamma^*\gamma^\to \pi^0$
transition form factor. Contents: (a) Pion DA in generalized QCD Sum Rules
(SRs); (b) Light Cone Sum Rules (LCSR) analysis of the CLEO data for the
$\gamma^*\gamma\to\pi^{0}$ transition form factor; (c) Recent lattice QCD data
for the pion DA; (d) BaBar data---a challenge for QCD?

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The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
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The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
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The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
9
The categories of this paper are: nlin
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The categories of this paper are: comp-gas
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom