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Register a new userFirst evidence of direct CP violation in charmless two-body decays of Bs mesons
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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$sigma$.
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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.
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.
Using the latest LHCb measurements of time-dependent CP violation in the B^0_s -> K^+K^- decay, a U-spin relation between the decay amplitudes of B^0_s -> K^+K^- and B^0 -> pi^+pi^- decay processes allows constraints to be placed on the angle gamma of the unitarity triangle and on the B^0_s mixing phase -2beta_s. Results from an extended approach, which uses additional inputs on B^0 -> pi^0pi^0 and B^+ -> pi^+pi^0 decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value gamma = ( 63.5 +7.2 -6.7 ) degrees modulo 180 degrees is determined. In an alternative analysis, the value -2beta_s = -0.12 +0.14 -0.16 rad is found. In both measurements, the uncertainties due to U-spin breaking effects up to 50% are included.
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.
We report final measurements of direct $mathit{CP}$--violating asymmetries in charmless decays of neutral bottom hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using the complete $sqrt{s}=1.96$ TeV proton-antiproton collisions data set, corresponding to 9.3 fb$^{-1}$ of integrated luminosity, we measure $mathcal{A}(Lambda^0_b rightarrow ppi^{-}) = +0.06 pm 0.07mathrm{(stat)} pm 0.03mathrm{(syst)}$ and $mathcal{A}(Lambda^0_b rightarrow pK^{-}) = -0.10 pm 0.08mathrm{(stat)} pm 0.04mathrm{(syst)}$, compatible with no asymmetry. In addition we measure the $mathit{CP}$--violating asymmetries in $B^0_s rightarrow K^{-}pi^{+}$ and $B^0 rightarrow K^{+}pi^{-}$ decays to be $mathcal{A}(B^0_s rightarrow K^{-}pi^{+}) = +0.22 pm 0.07mathrm{stat)} pm 0.02mathrm{(syst)}$ and $mathcal{A}(B^0 rightarrow K^{+}pi^{-}) = -0.083pm 0.013 mathrm{(stat)} pm 0.004mathrm{(syst)}$, respectively, which are significantly different from zero and consistent with current world averages.
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