Search forB*→B+γand limits on theB-meson mass

Abstract

The CUSB detector at the Cornell Electron Storage Ring was used to measure the inclusive photon spectrum at the ${\Upsilon }^{\prime \prime \prime }\mathrm{}\left(10.55\right)\mathrm{}$. In ∼5000 ${\Upsilon }^{\prime \prime \prime }$ events we see no obvious ∼50-MeV photon signal from $B^{*}\to B+\gamma$ decays and obtain an upper limit on the branching ratio for ${\Upsilon }^{\prime \prime \prime }\to B{B}^{*}$ of ∼10% with a 90% confidence level. From the lack of a photon signal and the observed width of the ${\Upsilon }^{\prime \prime \prime }$, we deduce limits on the $B$-meson mass of $\left[\frac{M\left({\Upsilon }^{\prime \prime \prime }\right)}{2-25} \mathrm{MeV}\right]<\mathrm{}{M}_B<[\frac{M\left({\Upsilon }^{\prime \prime \prime }\right)}{2}-10\mathrm{} \mathrm{MeV}]$.