Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comment on "Two-photon decay of the sigma meson"   We comment on a recent paper by Giacosa, Gutsche, and Lyobovitskij, in which
it is argued that a quarkonium interpretation of the $\sigma$ meson should give
rise to a much smaller two-photon decay width than commonly assumed. The reason
for this claimed discrepancy is a term in the transition amplitude, necessary
for gauge invariance, which allegedly is often omitted in the literature,
including the work of the present authors. Here we show their claims to be
incorrect by demonstrating, in the context of the Quark-Level Linear $\sigma$
Model, that the recently extracted experimental value
$\Gamma_{\sigma\to2\gamma}=(4.1\pm0.3)$ keV is compatible with a $q\bar{q}$
assignment for the $\sigma$, provided that meson loops are taken into account
as well.

21
The categories of this paper are: adap-org
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn