Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Test of the multiquark structure of $a_1(1420)$ in strong two-body
  decays   We present an analysis of strong two-body decays of the $a_1(1420)$ with
$J^{PC} = 1^{++}$ recently reported by the COMPASS Collaboration at CERN.
Following the interpretation of the COMPASS Collaboration that the $a_1$ is an
unusual state with a four-quark $q\bar q s \bar s$ structure we consider two
possible configurations for this state --- hadronic molecular and color
diquark-antidiquark structures. We find that the dominant decay mode of the
$a_1$ is the decay into $K$ and $K^*$. In particular, we calculate that the
four decay modes $a_1 \to VP$ with $VP = K^{*\pm}K^\mp$, $K^{*0}\bar K^0$,
$\bar K^{*0}K^0$ together give a dominant contribution to the measured total
width of about 150 MeV. The observational mode $a_1 \to f_0(980) + \pi^0$ is
significantly suppressed by one order of magnitude.

30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org