Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence of $\sigma$ particle in $J/\psi \to \omega \pi \pi$   Based on a sample of 7.8 million BESI $J/\psi$ events, the decay of $ J/\psi
\to \omega \pi^+ \pi^-$ is studied. A low mass enhancement in the $\pi^+ \pi^-$
invariant mass spectrum recoiling against $\omega$ particle is clearly seen
which does not come from the phase space effect and the background. According
to PWA analysis, this low mass enhancement is a broad $0^{++}$ resonance, the
$\sigma$ particle. If a Breit-Winger function of constant width is used to fit
the $\sigma$ signal, its mass and width are $384 \pm 66$ MeV and $458 \pm 100$
MeV respectively, which correspond to the pole position at (434 $\pm$ 78) - $i$
(202 $\pm$ 43) MeV.

35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat