Evidence for Isospin Violation and Measurement of CP Asymmetries in B →k∗ (892)γ

Abstract

We report the first evidence for isospin violation in B→K*γ and the first measurement of the difference of CP asymmetries between B+→K*+γ and B0→K*0γ. This analysis is based on the data sample containing 772×106BB¯ pairs that was collected with the Belle detector at the KEKB energy-asymmetric e+e- collider. We find evidence for the isospin violation with a significance of 3.1σ, Δ0+=[+6.2±1.5(stat)±0.6(syst)±1.2(f+-/f00)]%, where the third uncertainty is due to the uncertainty on the fraction of B+B- to B0B¯0 production in ϒ(4S) decays. The measured value is consistent with predictions of the standard model. The result for the difference of CP asymmetries is ΔACP=[+2.4±2.8(stat)±0.5(syst)]%, consistent with zero. The measured branching fractions and CP asymmetries for charged and neutral B meson decays are the most precise to date. We also calculate the ratio of branching fractions of B0→K*0γ to Bs0→ϕγ.