Tetraquark Interpretation of the BELLE Data on the Anomalous $\Upsilon${}(1S)$\pi${}+$\pi${}- and $\Upsilon${}(2S)$\pi${}+$\pi${}- Production near the $\Upsilon${}(5S) Resonance

Abstract

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-$\rightarrow${}$\Upsilon${}(1S)$\pi${}+$\pi${}-,$\Upsilon${}(2S)$\pi${}+$\pi${}- near the peak of the $\Upsilon${}(5S) resonance, which are found to be anomalously large in rates compared to similar dipion transitions between the lower $\Upsilon${} resonances. Assuming these final states arise from the production and decays of the JPC=1-- state Yb(10\,890), which we interpret as a bound (diquark-antidiquark) tetraquark state [bq][b\ifmmode\bar\else\textasciimacron\fi{}q\ifmmode\bar\else\textasciimacron\fi{}], a dynamical model for the decays Yb$\rightarrow${}$\Upsilon${}(1S)$\pi${}+$\pi${}-,$\Upsilon${}(2S)$\pi${}+$\pi${}- 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++ qq\ifmmode\bar\else\textasciimacron\fi{}-meson f2(1270). Our model provides excellent fits for the decay distributions, supporting Yb as a tetraquark state.