Measurement of the ratio of branching fractions B(B0 → K∗0γ )/B(B0 s → φγ ) and the direct CP asymmetry in B0 → K∗0γ

Abstract

The ratio of branching fractions of the radiative B decays B0→K∗0γ andB0s→φγ has been measured using an integrated luminosity of 1.0 fb−1 of pp collision data collected by the LHCb experiment at a centre-of-mass energy of √s=7 TeV. The value obtained is B(B0→K∗0γ)B(B0s→φγ )=1.23±0.06 (stat.)±0.04 (syst.)±0.10(fs/fd), where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the thirdis associated with the ratio of fragmentation fractions fs/fd. Using the world average value for B(B0→K∗0γ), the branching fractionB(B0s→φγ ) is measured to be(3.5±0.4)×10−5.The direct CP asymmetry in B0→K∗0γ decays has also been measured with the same data and found to be ACP(B0→K∗0γ)=(0.8±1.7(stat.)±0.9 (syst.))%. Both measurements are the most precise to date and are in agreement with the previous experimentalresults and theoretical expectations.