QCD Axial Anomaly Enhances the ηη′ Decay of the Hybrid Candidate η 1(1855)

Abstract

We study the hybrid mesons with the exotic quantum number I G J PC = 0+1−+ and investigate their decays into the η η′, a 1(1260) π, f 1(1285) η, f 1(1420) η, , , and channels. It is found that the QCD axial anomaly enhances the decay width of the η η′ channel although this mode is strongly suppressed by the small p-wave phase space. Our results support the interpretation of the η 1(1855) recently observed by BESIII as the hybrid meson of I G J PC = 0+1−+. The QCD axial anomaly ensures the η η′ decay mode to be a characteristic signal of the hybrid nature of the η 1(1855).