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

The ratio of branching fractions of the radiative B decays B0→K⁎0γ and B0s→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√=7TeV. 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 third is associated with the ratio of fragmentation fractions fs/fd. Using the world average value for B(B0→K⁎0γ), the branching fraction B(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 experimental results and theoretical expectations.