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Register a new userFirst observation of CP violation in the decays of Bs mesons
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Using pp collision data, corresponding to an integrated luminosity of $1.0 mathrm{fb}^{-1}$, collected by LHCb in 2011 at a center-of-mass energy of 7 TeV, we report the measurement of direct CP violation in $B^0_s to K^-pi^+$ decays, $A_{C/!P}(B^0_s rightarrow K^- pi^+)=0.27 pm 0.04,mathrm{(stat)} pm 0.01,mathrm{(syst)}$, with significance exceeding five standard deviations. This is the first observation of CP violation in the decays of $B^0_s$ mesons. Furthermore, we provide an improved determination of direct CP violation in $B^0 to K^+pi^-$ decays, $A_{C/!P}(B^0rightarrow K^+ pi^-)=-0.080 pm 0.007,mathrm{(stat)} pm 0.003,mathrm{(syst)}$, which is the most precise measurement of this quantity to date.
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Using a data sample corresponding to an integrated luminosity of 0.35 $mathrm{fb}^{-1}$ collected by LHCb in 2011, we report the first evidence of CP violation in the decays of $B^0_s$ mesons to $K^pm pi^mp$ pairs, $A_{CP}(B^0_s rightarrow K pi)=0.27 pm 0.08,mathrm{(stat)} pm 0.02,mathrm{(syst)}$, with a significance of 3.3$sigma$. Furthermore, we report the first observation of CP violation in $B^0$ decays at a hadron collider, $A_{CP}(B^0 rightarrow Kpi)=-0.088 pm 0.011,mathrm{(stat)} pm 0.008,mathrm{(syst)}$, with a significance exceeding 6$sigma$.
Direct and mixing-induced CP-violating asymmetries in Bs -> K+K- decays are measured for the first time using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb^{-1}, collected with the LHCb detector at a centre-of-mass energy of 7 TeV. The results are C_{KK} = 0.14 pm 0.11 pm 0.03 and S_{KK} = 0.30 pm 0.12 pm 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B0 -> pi+pi- decays to be C_{pipi} = -0.38 pm 0.15 pm 0.02 and S_{pipi} = -0.71 pm 0.13 pm 0.02, in good agreement with existing measurements.
The phenomenon of mixing in neutral meson systems has now been observed in all flavours, but only in the past year in the D0 system. The standard model anticipated that, for the charm sector, the mixing rate would be small, and also that CP violation, either in mixing or in direct decay, would be below the present levels of observability. It is hoped that further study of these phenomena might reveal signs of new physics. A review of recently available, experimental results is given.
Using data collected with the LHCb detector in proton-proton collisions at a centre-of-mass energy of 7 TeV, the hadronic decay Bs -> J/psi f0(980) is observed. This CP eigenstate mode could be used to measure mixing-induced CP violation in the B_s system. Using a fit to the pi+ pi- mass spectrum with interfering resonances gives R_{f0/phi} = [Gamma(Bs -> J/psi f0, f0 -> pi+ pi-)]/[Gamma(Bs -> J/psi phi, phi -> K+K-)] = 0.252^{+0.046+0.027}_{-0.032-0.033}, where the uncertainties are statistical and systematic, respectively.
An analysis of B+ to DK+ and B+ to Dpi+ decays is presented where the D meson is reconstructed in the two-body final states: K+pi-, K+K-, pi+pi- and pi+K-. Using 1.0 fb-1 of LHCb data, measurements of several observables are made including the first observation of the suppressed mode B+ to DK+, D to pi+K-. CP violation in B+ to DK+ decays is observed with 5.8 sigma significance.
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