Study on the radiative decays of Υ(nS)→ ηb+γ

الأصل · EN

In this work, we investigate the characteristics of the spin-singlet state ηb of the bottomonia family via the radiative decays of Υ(nS)→ ηb+γ. The theoretical estimation of the decay widths is carried out in terms of the light-front quark model (LFQM). Recently CLEO and BaBar collaborations have measured B(Υ(3S)→γηb) and the mass of ηb. In terms of the data we fix the concerned input parameters in our calculations of Υ(nS)→ ηb+γ. A special attention is paid on the transition of Υ(5S)→ ηb+γ. The BELLE data showed that the width of Υ(5S)→ Υ(2S,1S)+ππ is two orders larger than that of Υ(4S)→ Υ(2S,1S)+ππ, thus some theoretical explanations have been proposed. Among them, it is suggested the inelastic final state interaction (IFSI) Υ(5S)→ B B→ Υ(1S)+ππ may be a natural one. If so, a similar mechanism also applies to Υ(5S)→ B⁽*⁾ B⁽*⁾→ ηb+γ, the precise measurement would serve as a good test whether Υ(5S) possess exotic components. Our calculation in the LFQM indicates that the rate of the direct process Υ(5S)→ηb+γ is not anomalous compared to Υ(mS)→ηb+γ(m=1,2,3,4), thus if the IFSI does apply, the rate of Υ(5S)→ηb+γ should be larger than the others by orders.