Abstract
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08 ^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical, the second systematic and the third is associated to the ratio of fragmentation fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/- 0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be (3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.
Highlights
In the standard model (SM) the decays B0 ! KÃ0 and B0s ! 1 proceed at leading order through b ! s oneloop electromagnetic penguin transitions, dominated by a virtual intermediate top-quark coupling to a W boson
This paper presents a measurement of BðB0 ! KÃ0 Þ= BðB0s ! Þ using a strategy that ensures the cancellation of most of the systematic uncertainties affecting the measurement of the individual branching fractions
Electron, and hadron candidates are identified by a calorimeter system consisting of scintillating-pad and preshower detectors, an electromagnetic calorimeter (ECAL), and a hadronic calorimeter
Summary
In the standard model (SM) the decays B0 ! KÃ0 and B0s ! 1 proceed at leading order through b ! s oneloop electromagnetic penguin transitions, dominated by a virtual intermediate top-quark coupling to a W boson. In 2007, the Belle Collaboration reported the first observation of the analogous decay in the B0s sector, B0s ! The current world averages of the branching fractions of B0 ! Are ð4:33 Æ 0:15Þ Â 10À5 and ð5:7þÀ21::18Þ Â 10À5, respectively [4,5] These results are in agreement with the latest SM theoretical predictions from next-to-leading-order calculations using SCET [6], BðB0 ! The ratio of experimental branching fractions is measured to be BðB0 ! Þ using a strategy that ensures the cancellation of most of the systematic uncertainties affecting the measurement of the individual branching fractions. The measured ratio is used to determine BðB0s ! Þ, assuming the world average value of BðB0 !
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