Measurement of the ratio of branching fractions B(B0→K⁎0γ)/B(Bs0→ϕγ) and the direct CP asymmetry in B0→K⁎0γ

Abstract The ratio of branching fractions of the radiative B decays B 0 → K ⁎ 0 γ and B s 0 → 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 ( B 0 → K ⁎ 0 γ ) B ( B s 0 → ϕ γ ) = 1.23 ± 0.06 (stat.) ± 0.04 (syst.) ± 0.10 ( f s / f d ) , where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is associated with the ratio of fragmentation fractions f s / f d . Using the world average value for B ( B 0 → K ⁎ 0 γ ) , the branching fraction B ( B s 0 → ϕ γ ) is measured to be ( 3.5 ± 0.4 ) × 10 − 5 . The direct CP asymmetry in B 0 → K ⁎ 0 γ decays has also been measured with the same data and found to be A CP ( B 0 → 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.