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^\rm GJ^\rm 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) \overlineK, K_1(1270) \overlineK, and K_1(1400) \overlineK channels. It is found 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^\rm GJ^\rm 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).