Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Leading-twist two gluon distribution amplitude and exclusive processes
  involving eta and eta' mesons   I briefly review the formalism for treating the leading-twist two-gluon
states appearing in processes which involve eta and eta' mesons. The
constraints on the size of the lowest order Gegenbauer coefficients of the
two-gluon distribution amplitude are obtained from the fit to the eta and eta'
transition form factor data. The results are applied to chi -> eta eta (eta'
eta') decays and deeply virtual electroproduction of eta and eta' mesons.

9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga