Observation of a Fourth Upsilon State ine+e−Annihilations

Abstract

A fourth state in the upsilon energy region has been seen in $e^{+}{e}^{-}$ collisions at the Cornell Electron Storage Ring. A resonance is observed with a mass 1112±5 MeV above the lowest upsilon state. The 9.6-MeV rms width is greater than the 4.6-MeV energy resolution of the $e^{+}{e}^{-}$ beams. The observed characteristics of the new state make it a likely candidate for the $4{}_{}{}^3{}_{}{}^{}S$ state of the $b\overline{b}$ system, lying above the threshold for the production of $B$ mesons.