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Register a new userMeasurement of the flavour-specific CP-violating asymmetry $a_{rm sl}^s$ in $B_s^0$ decays
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The CP-violating asymmetry a_{sl}^s is studied using semileptonic decays of Bs and anti-Bs mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample corresponding to an integrated luminosity of 1.0/fb. The reconstructed final states are Ds^(+/-)mu ^(-/+), with the Ds^(+/-) particle decaying in the phipi^(+/-) mode. The Ds^(+/-)mu ^{-/+) yields are summed over Bs and anti-Bs initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain $a_{sl}^s$ = (-0.06 +/- 0.50 +/- 0.36)%, where the first uncertainty is statistical and the second systematic.
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A first flavour-tagged measurement of the time-dependent CP-violating asymmetry in $B_s^0 to phiphi$ decays is presented. In this decay channel, the CP-violating weak phase arises due to CP violation in the interference between $B_s^0$-$bar{B}_s^0$ mixing and the $b to s bar{s} s $ gluonic penguin decay amplitude. Using a sample of $pp$ collision data corresponding to an integrated luminosity of $1.0; fb^{-1}$ and collected at a centre-of-mass energy of $7 rm TeV$ with the LHCb detector, $880 B_s^0 to phiphi$ signal decays are obtained. The CP-violating phase is measured to be in the interval [-2.46, -0.76] rm rad$ at 68% confidence level. The p-value of the Standard Model prediction is 16%.
We report the measurements of the $CP$-violating parameters in $B_s^0 to D_s^{mp} K^{pm}$ decays observed in $pp$ collisions, using a data set corresponding to an integrated luminosity of $3.0,text{fb}^{-1}$ recorded with the LHCb detector. We measure $C_f = 0.73 pm 0.14 pm 0.05$, $A^{Delta Gamma}_f = 0.39 pm 0.28 pm 0.15$, $A^{Delta Gamma}_{overline{f}} = 0.31 pm 0.28 pm 0.15$, $S_f = -0.52 pm 0.20 pm 0.07$, $S_{overline{f}} = -0.49 pm 0.20 pm 0.07$, where the uncertainties are statistical and systematic, respectively. These parameters are used together with the world-average value of the $B_s^0$ mixing phase, $-2beta_s$, to obtain a measurement of the CKM angle $gamma$ from $B_s^0 to D_s^{mp} K^{pm}$ decays, yielding $gamma = (128,_{-22}^{+17})^circ$ modulo $180^circ$, where the uncertainty contains both statistical and systematic contributions. This corresponds to $3.8,sigma$ evidence for $CP$ violation in the interference between decay and decay after mixing.
A time-dependent analysis of the $B_s^0 to phigamma$ decay rate is performed to determine the $CP$-violating observables $S_{phigamma}$ and $C_{phigamma}$, and the mixing-induced observable $mathcal{A}^{Delta}_{phigamma}$. The measurement is based on a sample of $pp$ collision data recorded with the LHCb detector, corresponding to an integrated luminosity of 3 fb$^{-1}$ at center-of-mass energies of 7 and 8 TeV. The measured values are begin{align*} S_{phigamma} &= 0.43 pm 0.30 pm 0.11, C_{phigamma} &= 0.11 pm 0.29 pm 0.11, mathcal{A}^{Delta}_{phigamma} &= -0.67 , ^{+0.37}_{-0.41} pm 0.17, end{align*} where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables $S$ and $C$ in radiative $B_s^0$ decays. The results are consistent with the Standard Model predictions.
The $CP$ asymmetry in the mixing of $B_s^0$ and $overline{B}{}_s^0$ mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0 fb$^{-1}$, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Semileptonic $B_s^0$ and $overline{B}{}_s^0$ decays are studied in the inclusive mode $D_s^{mp} mu^{pm} u_{mu} X$ with the $D_s^{mp}$ mesons reconstructed in the $K^+ K^- pi^{mp}$ final state. Correcting the observed charge asymmetry for detection and background effects, the $CP$ asymmetry is found to be $a_{text{sl}}^s = (0.39 pm 0.26 pm 0.20) % $, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of $a_{text{sl}}^s$ to date. It is consistent with the prediction from the Standard Model and will constrain new models of particle physics.
The first measurement of decay-time-dependent CP asymmetries in the decay $B_s^0rightarrow J/psi K_{rm S}^0$ and an updated measurement of the ratio of branching fractions $mathcal{B}(B_s^0rightarrow J/psi K_{rm S}^0)/mathcal{B}(B_d^0rightarrow J/psi K_{rm S}^0)$} are presented. The results are obtained using data corresponding to an integrated luminosity of 3.0 fb$^{-1}$ of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The results on the CP asymmetries are $A_{DeltaGamma}(B_s^0rightarrow J/psi K_{rm S}^0) = 0.49_{-0.65}^{+0.77}(stat) pm 0.06(syst)$, $C_{rm dir}(B_s^0rightarrow J/psi K_{rm S}^0) = -0.28 pm 0.41(stat) pm 0.08(syst)$ and $S_{rm mix}(B_s^0rightarrow J/psi K_{rm S}^0) = -0.08 pm 0.40(stat) pm 0.08(syst)$. The ratio $mathcal{B}(B_s^0rightarrow J/psi K_{rm S}^0)/mathcal{B}(B_d^0rightarrow J/psi K_{rm S}^0)$ is measured to be $0.0431 pm 0.0017(stat) pm 0.0012(syst) pm 0.0025(f_s/f_d)$, where the last uncertainty is due to the knowledge of the $B_s^0$ and $B_d^0$ production fractions.
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