Measurement of the Ratio of Branching Fractions B(B0 → K∗0 γ)/B(B0s → ϕ γ) and the Direct CP Asymmetry in B0 → K∗0 γ

The ratio of branching fractions of the radiative B decays B0 → K∗0 γ and B0s → ϕ γ 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∗0 γ)/B(B0s → ϕ γ) = 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∗0 γ), the branching fraction B(B0s → ϕ γ) is measured to be (3.5 ± 0.4) x 10^−5. The direct CP asymmetry in B0 → K∗0 γ decays has also been measured with the same data and found to be A_CP(B0 → K∗0 γ) = (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.