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Register a new userDetermination of gamma and -2beta_s from charmless two-body decays of beauty mesons
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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.
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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$sigma$.
A search for the non-resonant decays $B^0_s rightarrow mu^{+}mu^{-}mu^{+}mu^{-}$ and $B^0 rightarrow mu^{+}mu^{-}mu^{+}mu^{-}$ is presented. The measurement is performed using the full Run 1 data set collected in proton-proton collisions by the LHCb experiment at the LHC. The data correspond to integrated luminosities of $1$ and $2~mathrm{fb}^{-1}$ collected at centre-of-mass energies of $7$ and $8~mathrm{TeV}$, respectively. No signal is observed and upper limits on the branching fractions of the non-resonant decays at $95%$ confidence level are determined to be mathcal{B}(B^0_s rightarrow mu^{+}mu^{-}mu^{+}mu^{-}) & < 2.5 times 10^{-9} mathcal{B}(B^0 rightarrow mu^{+}mu^{-}mu^{+}mu^{-}) & < 6.9 times 10^{-10}.
Based on data corresponding to an integrated luminosity of 0.37 fb^-1 collected by the LHCb experiment in 2011, the following ratios of branching fractions are measured: B(B0 -> pi+ pi-) / B(B0 -> K+pi-) = 0.262 +/- 0.009 +/- 0.017, (fs/fd) * B(Bs -> K+K-) / B(B^0 -> K+pi-) = 0.316 +/- 0.009 +/- 0.019, (fs/fd) * B(Bs ->pi+ K-) / B(B0 -> K+pi-) = 0.074 +/- 0.006 +/- 0.006, (fd/fs) * B(B0 -> K+K-) / B(Bs -> K+K-) = 0.018 {+ 0.008 - 0.007} +/- 0.009, (fs/fd) * B(Bs -> pi+pi-) / B(B0 -> pi+pi-) = 0.050 {+ 0.011 - 0.009} +/- 0.004, B(Lambda_b -> p pi-) / B(Lambda_b -> p K-) = 0.86 +/- 0.08 +/- 0.05, where the first uncertainties are statistical and the second systematic. Using the current world average of B(B0 -> K+pi-) and the ratio of the strange to light neutral B meson production fs/fd measured by LHCb, we obtain: B(B0 -> pi+pi-) = (5.08 +/- 0.17 +/- 0.37) x 10^-6, B(Bs -> K+K-) = (23.0 +/- 0.7 +/- 2.3) x 10^-6, B(Bs -> pi+K-) = (5.4 +/- 0.4 +/- 0.6) x 10^-6, B(B0 -> K+K-) = (0.11 {+ 0.05 - 0.04} +/- 0.06) x 10^-6, B(Bs -> pi+pi-) = (0.95 {+ 0.21 - 0.17} +/- 0.13) x 10^-6. The measurements of B(Bs -> K+K-), B(Bs -> pi+ K-) and B(B0 -> K+K-) are the most precise to date. The decay mode Bs -> pi+pi- is observed for the first time with a significance of more than 5 sigma.
Results are presented on the study of three body decays of D0 -> K0s h+ h-, where h=pi/K and DS+ -> K0S K0S pi+. The data have been collected by the BaBar experiment at SLAC and are extracted from continuum e+ e- annihilations at the Upsilon(4S) energy.
A search for $CP$ violation in charmless four-body decays of $Lambda_b$ and $Xi_b^0$ baryons with a proton and three charged mesons in the final state is performed. To cancel out production and detection charge-asymmetry effects, the search is carried out by measuring the difference between the $CP$ asymmetries in a charmless decay and in a decay with an intermediate charmed baryon with the same particles in the final state. The data sample used was recorded in 2011 and 2012 with the LHCb detector and corresponds to an integrated luminosity of $3 {rm fb}^{-1}$. A total of 18 $CP$ asymmetries are considered, either accounting for the full phase space of the decays or exploring specific regions of the decay kinematics. No significant $CP$-violation effect is observed in any of the measurements.
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