Measurement of the Ratio of Branching Fractions Br(B$0\atop{s}$ → D$-\atop{s}$ π<sup>+</sup>)/Br(B<sup>0</sup> → D<sup>-</sup> π<sup>+</sup>) at CDF-II

Abstract

The measurement of B$0\atop{s}$ mixing is one of the flagship analyses for the Run II B physics program. The sensitivity of the measurement to the frequency of B$0\atop{s}$ oscillations strongly depends on the number of reconstructed B$0\atop{s}$ mesons. They present the measurement of the ratio of branching fractions Br(B$0\atop{s}$ → D$-\atop{s}$π+)/Br(B0 → D-π+), which directly influences the number of B$0\atop{s}$ events available for the measurement of B$0\atop{s}$ mixing at CDF-II. They analyze 115 pb-1 of data collected with the CDF-II detector in p$\bar{p}$ collisions at √s = 1.96 TeV using a novel displaced track trigger. They reconstruct 78 ± 11 B$0\atop{s}$ → D$-\atop{s}$π+ decays at 1153 ± 45 B0 → D-π+ decays with good signal to background ratio. This is the world's largest sample of fully reconstructed B$0\atop{s}$ → D$-\atop{s}$π+ decays. They find the ratio of production fractions multiplied by the ratio of branching fractions to be: fs/fd • Br(B$0\atop{s}$ → D$-\atop{s}$π+)/Br(B0 → D-π+) = 0.325 ± 0.046(stat) ± 0.034(syst) ± 0.084 (BR). Using the world average value of fs/fd = 0.26 ± 0.03, we infer that the ratio of branching fractions is: Br(B$0\atop{s}$ → D$-\atop{s}$π+)/Br(B0 → D-π+) = 1.25 ± 0.18(stat) ± 0.13(syst) ± 0.32(BR) ± 0.14(PR) where the last uncertainty is due to the uncertainty on the world average measurement of the ratio of B$0\atop{s}$ to B0 production rates, fs/fd.