Measurement of the branching fractions and CP-asymmetry of B^- -> D^0_(CP) K^- decays with the BaBar detector

Abstract

We present a study of B- -> D^0_CP K^- decays, where D^0_CP is reconstructed in CP-even channels, based on a sample of 88.8 million Upsilon(4S)->BBbar decays collected with the BaBar detector at the PEP-II e^+e^- storage ring. We measure the ratio of Cabibbo-suppressed to Cabibbo-favored branching fractions Br(B- -> D^0_CP K^-)/Br(B- -> D^0_CP pi^-)= (8.8 +/- 1.6(stat) +/- 0.5(syst))\times 10^{-2} and the CP asymmetry A_CP= 0.07 +/- 0.17(stat) +/- 0.06(syst). We also measure Br(B- ->D0K-)/Br(B- ->D0pi-)=(8.31 +/- 0.35(stat) +/- 0.20(syst))\times 10^{-2} using a sample of 61.0 million BBbar pairs.