Tetraquark interpretation of the BELLE data on the anomalous ${\rm Y}(1S){\pi }^{+}{\pi }^{-}$ and ${\rm Y}(2S){\pi }^{+}{\pi }^{-}$ production near the ${\rm Y}(5S)$ resonance

Abstract

We analyze the Belle data [K. F. Chen {\it et al.} (Belle Collaboration), Phys.\ Rev.\ Lett.\ {\bf 100}, 112001 (2008); I. Adachi {\it et al.} (Belle Collaboration), arXiv:0808.2445] on the processes $e^{+}{e}^{-}\to {\rm Y}(1S){\pi }^{+}{\pi }^{-},{\rm Y}(2S){\pi }^{+}{\pi }^{-}$ near the peak of the ${\rm Y}(5S)$ resonance, which are found to be anomalously large in rates compared to similar dipion transitions between the lower ${\rm Y}$ 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 $[bq][\bar{b}\bar{q}]$, a dynamical model for the decays $Y_b\to {\rm Y}(1S){\pi }^{+}{\pi }^{-},{\rm Y}(2S){\pi }^{+}{\pi }^{-}$ 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 $2^{++}$ $q\bar{q}$-meson $f_2(1270)$. Our model provides excellent fits for the decay distributions, supporting $Y_b$ as a tetraquark state.

Comments: 4 pages, 2 figures, 3 tables; Abstract and Figures 1 & 2 modified; small changes in the text; some references added; version corresponds to the journal article