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Register a new userMeasurement 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
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The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma and Bs0 phi gamma 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 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 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 BR(B0 -> K*0 gamma), the branching fraction BR(Bs0 -> phi gamma) is measured to be (3.5 +/- 0.4) x 10^{-5}. The direct CP asymmetry in B0 -> K*0 gamma decays has also been measured with the 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 the previous experimental results and theoretical expectations.
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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.
We study the decays B- --> D*0 pi- and B- --> D*0 K-, where the D*0 decays into D0 pi0, with the D0 reconstructed in the CP-even (CP+) eigenstates K- K+ and pi- pi+ and in the (non-CP) channels K- pi+, K- pi+ pi+ pi-, and K- pi+ pi0. Using a sample of about 123 million BBbar pairs, we measure the ratios of decay rates R*(non-CP)=BR(B- --> D*0(non-CP) K-)/BR(B- --> D*0(non-CP) pi-) = 0.0813+-0.0040(stat)+0.0042-0.0031}(syst), and provide the first measurements of R*(CP+)= BR(B- --> D*0(CP+) K-)/BR(B- --> D*0(CP+) pi-) = 0.086+-0.021(stat)+-0. 007(syst), and of the CP asymmetry A*(CP+) = (BR(B- --> D*0(CP+) K-) - BR(B+ --> D*0(CP+) K+))/(BR(B- --> D*0(CP+) K-) + BR(B+ --> D*0(CP+) K+)) = -0.10+-0.23(stat)+0.03-0.04(syst).
A measurement of the CP asymmetry in B0 -> K*0 mu+ mu- decays is presented, based on 1.0fb-1 of pp collision data recorded by the LHCb experiment during 2011. The measurement is performed in six bins of invariant mass squared of the mu+ mu- pair, excluding the J/psi and psi(2S) resonance regions. Production and detection asymmetries are removed using the B0 -> J/Psi K*0 decay as a control mode. The integrated CP asymmetry is found to be -0.072 +- 0.040 (stat.) +- 0.005 (syst.), consistent with the Standard Model.
We present a study of the decays B- --> D*0 pi- and B- --> D*0 K-, where the D*0 decays into D0 pi0, with the D0 reconstructed in the CP eigenstates K- K+ and pi- pi+ and in the (non-CP) channels K- pi+, K- pi+ pi+ pi-, and K- pi+ pi0. We use an unbinned maximum likelihood fit to measure the signal yields. Using a sample of about 123 million Y(4S) decays into B anti-B pairs, we measure the ratios of decay rates R*(CP+)=BR(B- --> D*0(CP+) K-)/BR(B- --> D*0(CP+) pi-) = 0.088+-0.021(stat)+0.007-0.005(syst), and provide the first measurements of R*(non-CP) = BR(B- --> D*0(non-CP) K-)/BR(B- --> D*0(non-CP) pi-) = 0.0805+-0.0040(stat)+0.0039-0.0032(syst), and of the CP asymmetry A*(CP+) = (BR(B- --> D*0(CP+) K-)-BR(B+ --> D*0(CP+) K+))/(BR(B- --> D*0(CP+) K-)+BR(B+ --> D*0(CP+) K+)) = -0.02+-0.24(stat)+-0.05(syst). These results are preliminary.
The decay B0 -> D K*0 and the charge conjugate mode are studied using 1.0fb-1 of pp collision data collected by the LHCb experiment at sqrt(s) = 7TeV in 2011. The CP asymmetry between the B0 -> D K*0 and the B0bar -> D K*0bar decay rates, with the neutral D meson in the CP-even final state K+K-, is found to be A_d_KK = -0.45 +- 0.23 +- 0.02, where the first uncertainty is statistical and the second is systematic. In addition, favoured B0 -> D K*0 decays are reconstructed with the D meson in the non-CP eigenstate K+ pi-. The ratio of the B-flavour averaged decay rates in D decays to CP and non-CP eigenstates is measured to be R_d_KK = 1.36 (+0.37) (-0.32) +- 0.07, where the ratio of the branching fractions of D0 -> K- pi+ to D0 -> K+ K- decays is included as multiplicative factor. The CP asymmetries measured with two control channels, the favoured B0 -> DK*0 decay with D -> K+ pi- and the Bs0bar -> D K*0 decay with D K+ K-, are also reported.
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