| 摘要: |
The BESIII Collaboration recently reported the observation of the a(0) (980)(0) - f(0) (980) mixing in the isospin-breaking decay J/psi -> eta pi(0)phi. In the Dalitz plot for that decay with the ti reconstructed from two photons, there is a band around 1.4 GeV on the pi(0)phi distribution. In general, this peak can be due to a resonance or a kinematic effect. In this paper, we study the effects of a set of K*K (K) over bar triangle diagrams and show that due to triangle singularities such diagrams can lead to a peak around 1.4 GeV in the pi(0)phi invariant mass distribution, which is a model-independent conclusion. The Dalitz plot induced by such a mechanism has a feature consistent with the BESIII observation; namely, events along the band accumulate at both ends close to the Dalitz plot boundary. The effects of the same mechanism on the J/psi -> pi(0)pi(0)phi and J/psi -> eta pi(K+K-)-K-0 decays are also investigated. We suggest to take more data for the J/psi ->eta pi(0)phi -> eta pi(K+K-)-K-0 and check whether the structure around 1.4 GeV persists for the K+K- invariant mass away from the phi mass region. This is crucial for understanding whether the band is due to triangle singularities or due to a resonance. Were it the latter, the band should remain, while it would not if it is due to the former. |
