Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theoretical study on \eta'--> 4 pions   The $\eta'$ meson is associated with the U(1) anomaly. In this paper, a
successful effective chiral theory of mesons has been applied to study the
anomalous decay of $\eta'\rightarrow \pi^+\pi^-\pi^{+(0)}\pi^{-(0)}$. In this
study, the contributions of triangle and box anomalies are calculated. It is
shown that the contribution of box diagrams is important in this process. We
predict branching ratios of $Br(\eta' \rightarrow \pi^+ \pi^- \pi^+ \pi^-)={1
\over 2}Br(\eta' \rightarrow \pi^+ \pi^- \pi^0 \pi^0) = (8.3 \pm 1.2) \times
10^{-5}$, which is in good agreement with BESIII measurement.

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
4
The categories of this paper are: cond-mat
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th