MEASUREMENTS OF BRANCHING FRACTIONS AND CP VIOLATING ASYMMETRIES IN B0 ---> PI+ PI-, K+ PI-, K+ K- DECAYS

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 Υ(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 Β(B0 → π+π-) = (4.7 ± 0.6 ± 0.2) x 10-6 and Β(B0 → K+π-) = (17.9±0.9±0.7) x 10-6, where the first uncertainty is statistical and the second is systematic; the 90% confidence level upper limit Β(B0 → K+K-) < 0.6 x 10-6; and the direct CP-violating charge asymmetry AKπ = -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 B0 → π+π- decays with a time-dependent fit and find Sππ = 0.02 ± 0.34 ± 0.05 [-0.54, +0.58] and Cππ = -0.30 ± 0.25 ± 0.04 [-0.72, +0.12]