Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) and the direct CP asymmetry in B0 -> K*0 gamma

摘要

The ratio of branching fractions of the radiative B decays B0 -> K*0 gammaand Bs0 phi gamma has been measured using an integrated luminosity of 1.0 fb-1of pp collision data collected by the LHCb experiment at a centre-of-massenergy of sqrt(s)=7 TeV. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 ->phi gamma) = 1.23 +/- 0.06(stat.) +/- 0.04(syst.) +/- 0.10(fs/fd), where thefirst uncertainty is statistical, the second is the experimental systematicuncertainty and the third is associated with the ratio of fragmentationfractions fs/fd. Using the world average value for BR(B0 -> K*0 gamma), thebranching fraction BR(Bs0 -> phi gamma) is measured to be (3.5 +/- 0.4) x10^{-5}. The direct CP asymmetry in B0 -> K*0 gamma decays has also been measured withthe same data and found to be A(CP)(B0 -> K*0 gamma) = (0.8 +/- 1.7(stat.) +/-0.9(syst.))%. Both measurements are the most precise to date and are in agreement with theprevious experimental results and theoretical expectations.