Tetraquark Interpretation of the BELLE Data on the Anomalous Υ(1S)π+π- and Υ(2S)π+π- Production near the Υ(5S) Resonance
We analyze the Belle data [K. F. Chen (Belle Collaboration), Phys. Rev. Lett. 100, 112001 (2008); PRLTAO0031-900710.1103/PhysRevLett.100.112001I. Adachi (Belle Collaboration), arXiv:0808.2445] on the processes e+e-→Υ(1S)π+π-,Υ(2S)π+π- near the peak of the Υ(5S) resonance, which are found to be anomalously large in rates compared to similar dipion transitions between the lower Υ resonances. Assuming these final states arise from the production and decays of the JPC=1-- state Yb(10890), which we interpret as a bound (diquark-antidiquark) tetraquark state [bq][b̄q̄], a dynamical model for the decays Yb→Υ(1S)π+π-,Υ(2S)π+π- is presented. Depending on the phase space, these decays receive significant contributions from the scalar 0++ states, f0(600) and f0(980), and from the 2++ qq̄-meson f2(1270). Our model provides excellent fits for the decay distributions, supporting Yb as a tetraquark state.