Measurements of Branching Fractions and CP-violating Asymmetries in B0->pi+ pi-, K+ pi-, K+ K- Decays

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  • 24 July 2002
Abstract
We present measurements of branching fractions and CP-violating asymmetries for neutral B meson decays to two-body final states of charged pions and kaons. The results are obtained from a data sample of about 88 million Upsilon(4S) --> B bar{B} decays collected between 1999 and 2002 with the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. From a time-independent fit we measure the charge-averaged branching fractions Br(B^0 --> pi^+ pi^-) = (4.7 +/- 0.6 +/- 0.2) times 10^{-6} and Br(B^0 --> K^+ pi^-) = (17.9 +/- 0.9 +/- 0.7) times 10^{-6}, where the first uncertainty is statistical and the second is systematic; the 90% confidence level upper limit Br(B^0 --> K^+ K^-) < 0.6 times 10^{-6}; and the direct CP-violating charge asymmetry A_{K pi} = -0.102 +/- 0.050 +/- 0.016 [-0.188,-0.016], where the range in square brackets indicates the 90% confidence interval. We measure the CP-violating parameters in B^0 --> pi^+ pi^- decays with a time-dependent fit and find S_{pi pi} = 0.02 +/- 0.34 +/- 0.05 [-0.54,+0.58] and C_{pi pi} = -0.30 +/- 0.25 +/- 0.04 [-0.72,+0.12].

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