Measurement of sin(2α) at B aB ar

Abstract

We present updated 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 60 million ϒ(4S) → B B decays collected between 1999 and 2001 by the B aB ar detector at the PEP-II asymmetric-energy B Factory at SLAG. The sample contains 124 −02 +16 ππ, 403 ± 24 Kπ, and 0.6 −7.4 +8.0 KK candidates, from which we measure the following quantities: B( B 0 → π + π −) = (5.4 ± 0.7 ± 0.4) × 10 −6, B( B ) → K + π −) = (17.8 ± 1.1 ± 0.8) × 10 −6, B( B 0 → K + K −) < 1.1 × 10 −6 (90% C.L.), A Kπ = −0.05 ± 0.06 ± 0.01 [−0.14, +0.05], S ππ = −0.01 ± 0.37 ± 0.07 [−0.66, +0.62], C ππ = -0.02 ± 0.29 ± 0.07 [−0.54, +0.48], where the errors are statistical and systematic, respectively, and the asymmetry limits correspond to the 90% confidence level. These results are preliminary.