Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Interference in the reaction $e^+e^-\to\gamma\pi^+\pi^-$ and the final
  state interaction   We describe the interference between amplitudes $e^ +
e^-\to\rho\to\gamma\pi^+\pi^-$ and $e^ + e^-\to\phi\to\gamma (f_0 + \sigma)
\to\gamma\pi^ + \pi^-$, with regard to the phase of the elastic $\pi\pi$
scattering background and mixing of the $f_0$ and $\sigma$ mesons. It is shown
that the Fermi-Watson theorem for the final state interaction in the reaction
$e^ + e^-\to\rho\to\gamma\pi^ + \pi^-$ is not valid in the case of soft
photons, $\omega < 100$ MeV, in the $\phi$ meson region. The interference
patterns in the spectrum of the photon energy differential cross-section and in
the full cross-section as a function of the beam energy are obtained.

10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex