Measurement of the time-dependent CP asymmetries in $B_s^0rightarrow J/psi K_{rm S}^0$

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.

Measurement of the effective B_s^0 -> J/{psi} K_S^0 lifetime

This paper reports the first measurement of the effective B_s^0 -> J/{psi} K_S^0 lifetime and an updated measurement of its time-integrated branching fraction. Both measurements are performed with a data sample, corresponding to an integrated luminosity of 1.0 fb^{-1} of pp collisions, recorded by the LHCb experiment in 2011 at a centre-of-mass energy of 7 TeV. The results are: tau_J/{psi}K_S^0 = 1.75 +/- 0.12 (stat) +/- 0.07 (syst) and BR(B_s^0 -> J/{psi} K_S^0) = (1.97 +/- 0.23) X 10^{-5}. For the latter measurement, the uncertainty includes both statistical and systematic sources.