Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unified dispersive approach to $\gamma^*\to\gamma\pi\pi$ and
  $\gamma\gamma\to\pi\pi$   A representation of the amplitude $\gamma^*(q^2)\to\gamma\pi\pi$ is proposed
which combines large $N_c$ chiral resonance Lagrangian modelling with general
unitarity and analyticity properties. The amplitude is constrained from
$\gamma\gamma$ scattering results and $e^+ e^- \to\gamma\pi^0\pi^0$
measurements by the CMD-2 and SND collaborations. As an application, the
contribution of the $\pi\pi+\gamma$ states in the HVP contribution to the muon
$g-2$ are reconsidered, taking into account the effect of the strong $S$-wave
$\pi\pi$ rescattering in a model independent way.

30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat