Tetraquark Interpretation of the BELLE Data on the Anomalous γ(1S)π+ π- and γ(2S)π+ π- Production near the γ(5S) Resonance

We analyze the Belle data [K. F. Chen et al. (Belle Collaboration), Phys. Rev. Lett. 100, 112001 (2008); I. Adachi et al. (Belle Collaboration), arXiv:0808.2445] on the processes e(+)e(-) -> gamma(1S)pi(+) pi(-), gamma(2S)pi(+) pi(-) near the peak of the gamma(5S) resonance, which are found to be anomalously large in rates compared to similar dipion transitions between the lower gamma resonances. Assuming these final states arise from the production and decays of the J(PC) = 1(--) state Y-b (10890), which we interpret as a bound (diquark- antidiquark) tetraquark state [bq][(b) over bar(q) over bar], a dynamical model for the decays Y-b -> gamma(1S)pi(+)pi(-),gamma(2S)pi(+)pi(-) is presented. Depending on the phase space, these decays receive significant contributions from the scalar 0(++) states, f(0) (600) and f(0)(980), and from the 2(++) q (q) over bar -meson f(2)(1270). Our model provides excellent fits for the decay distributions, supporting Yb as a tetraquark state.