Measurement of B(Υ(5S)→Bs(*)B̄s(*)) using mesons

Abstract

Knowledge of the Bs decay fraction of the Υ(5S) resonance, fS, is important for Bs meson studies at the Υ(5S) energy. Using a data sample collected by the CLEO III detector at CESR consisting of 0.423fb-1 on the Υ(5S) resonance, 6.34fb-1 on the Υ(4S) and 2.32fb-1 in the continuum below the Υ(4S), we measure B(Υ(5S)→ X)=(13.8±0.7-1.5+2.3) % and B(Υ(4S)→ X)=(7.1±0.1±0.6)%; the ratio of the two rates is (1.9±0.1-0.2+0.3). This is the first measurement of the meson yield from the Υ(5S). Using these rates, and a model dependent estimate of B(Bs→ X), we determine fS=(24.6±2.9-5.3+11.0)%. We also update our previous independent measurement of fS made using the inclusive Ds yields to now be (16.8±2.6-3.4+6.7)%, due to a better estimate of the number of hadronic events. We also report the total Υ(5S) hadronic cross section above continuum to be σ(e+e-→Υ(5S))=(0.301±0. 002±0.039)nb. This allows us to extract the fraction of B mesons as (58.9±10.0±9.2)%, equal to 1-fS. Averaging the three methods gives a model dependent result of fS=(21-3+6)%. © 2007 The American Physical Society.