Observation of theϒ′′′at the Cornell Electron Storage Ring

Abstract

During an energy scan at the Cornell Electron Storage Ring, with use of the Columbia University-Stony Brook NaI detector, an enhancement in $\sigma (e^{+}{e}^{-}\to \mathrm{hadrons})$ is observed at center-of-mass energy ∼10.55 GeV. The mass and leptonic width of this state (${\Upsilon }^{\prime \prime \prime }$) suggest that it is the $4{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ bound state of the $b$ quark and its antiquark. After applying to the data a cut in a (pseudo) thrust variable, the natural width is measured to be $\Gamma =12.6\mathrm{}\pm 6.0$ MeV, indicating that the ${\Upsilon }^{\prime \prime \prime }$ is above the threshold for $B\overline{B}$ production.