Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: QCD axial anomaly enhances the $\eta \eta^\prime$ decay of the hybrid
  candidate $\eta_1(1855)$   We study the hybrid mesons with the exotic quantum number $I^GJ^{PC} =
0^+1^{-+}$ and investigate their decays into the $\eta \eta^\prime$, $a_1(1260)
\pi$, $f_1(1285) \eta$, $f_1(1420) \eta$, $K^*(892) \bar K$, $K_1(1270) \bar
K$, and $K_1(1400) \bar K$ channels. We find that the QCD axial anomaly
enhances the decay width of the $\eta \eta^\prime$ channel although this mode
is strongly suppressed by the small $P$-wave phase space. Our results support
the interpretation of the $\eta_1(1855)$ recently observed by BESIII as the
$\bar s s g$ hybrid meson of $I^GJ^{PC}=0^+1^{-+}$. The QCD axial anomaly
ensures the $\eta \eta^\prime$ decay mode to be a characteristic signal of the
hybrid nature of the $\eta_1(1855)$.

28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin