Branching Fractions and CP Asymmetries in B0→π0π0, B+→π+π0, and B+→K+π0 Decays and Isospin Analysis of the B→ππ System

Abstract

Based on a sample of 227 × 10 6 B ¯¯¯ B pairs collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure the branching fraction B ( B 0 → π 0 π 0 ) = ( 1.17 ± 0.32 ± 0.10 ) × 10 − 6 , and the asymmetry C π 0 π 0 = − 0.12 ± 0.56 ± 0.06 . The B 0 → π 0 π 0 signal has a significance of 5.0 σ . We also measure B ( B + → π + π 0 ) = ( 5.8 ± 0.6 ± 0.4 ) × 10 − 6 , B ( B + → K + π 0 ) = ( 12.0 ± 0.7 ± 0.6 ) × 10 − 6 , and the charge asymmetries A π + π 0 = − 0.01 ± 0.10 ± 0.02 and A K + π 0 = 0.06 ± 0.06 ± 0.01 . Using isospin relations, we find an upper bound on the angle difference | α − α eff | of 35° at the 90% C.L.