Measurement of B(Upsilon(5S)-> B-s((*))(B)over-bar(s)((*))) using phi mesons

Knowledge of the B-s decay fraction of the Upsilon(5S) resonance, f(S), is important for B-s meson studies at the Upsilon(5S) energy. Using a data sample collected by the CLEO III detector at CESR consisting of 0.423 fb(-1) on the Upsilon(5S) resonance, 6.34 fb(-1) on the Upsilon(4S) and 2.32 fb(-1) in the continuum below the Upsilon(4S), we measure B(Upsilon(5S)->phi X)=(13.8 +/- 0.7(-1.5)(+2.3))% and B(Upsilon(4S)->phi 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 phi meson yield from the Upsilon(5S). Using these rates, and a model dependent estimate of B(B-s ->phi X), we determine f(S)=(24.6 +/- 2.9(-5.3)(+11.0))%. We also update our previous independent measurement of f(S) made using the inclusive D-s 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 Upsilon(5S) hadronic cross section above continuum to be sigma(e(+)e(-)->Upsilon(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-f(S). Averaging the three methods gives a model dependent result of f(S)=(21(-3)(+6))%.