Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-photon decays and transition form factors of $\pi^0$, $\eta$, and
  $\eta'$ in large-$N_c$ chiral perturbation theory   We present a calculation of $P\to \gamma^{(\ast)}\gamma^{(\ast)}$ processes,
where $P=\pi^0,\ \eta,\ \eta'$, at the one-loop level up to and including
next-to-next-to-leading order (NNLO) in large-$N_c$ chiral perturbation theory.
The results are numerically evaluated successively at LO, NLO, and NNLO. The
appearing low-energy constants are determined through fits to the available
experimental data. We investigate the decay widths to real photons, the
single-virtual transition form factors, and the widths of $P\to\gamma l^+l^-$,
where $l=e,\ \mu$. Furthermore, we provide results for the slopes and
curvatures of the transition form factors.

1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph