Bsemileptonic decays at the Υ(4S) and the Υ(5S)

Abstract

B-meson semileptonic decay spectra have been obtained at the Υ(4S) and at the Υ(5S) at the Cornell Electron Storage Ring with the Columbia University–Stony Brook detector. The branching ratio for B→eνX at the Υ(4S) is found to be (10.0±0.5)%. The electron spectrum of B→eνX at the Υ(5S) is observed for the first time and the average branching ratio of B,${\mathit{B}}_{\mathit{s}}$→eνX is consistent with that for B’s from Υ(4S) decays. The shape of the electron spectrum at the Υ(5S) indicates production of B mesons which are heavier than nonstrange B’s, presumably strange B’s.