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Register a new userMeasurement of the $B_s^0to J/psi K_S^0$ branching fraction
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The $B_s^0to J/psi K_S^0$ branching fraction is measured in a data sample corresponding to 0.41$fb^{-1}$ of integrated luminosity collected with the LHCb detector at the LHC. This channel is sensitive to the penguin contributions affecting the sin2$beta$ measurement from $B^0to J/psi K_S^0$ The time-integrated branching fraction is measured to be $BF(B_s^0to J/psi K_S^0)=(1.83pm0.28)times10^{-5}$. This is the most precise measurement to date.
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A measurement of the branching fraction of the decay $B_s^0 to K_S^0 K_S^0$ is performed using proton-proton collision data corresponding to an integrated luminosity of 5 $fb^{-1}$ collected by the LHCb experiment between 2011 and 2016. The branching fraction is determined to be BR($B_s^0 to K_S^0 K_S^0$) = [8.3 $pm$ 1.6 (stat) $pm$ 0.9 (syst) $pm$ 0.8 (norm) $pm$ 0.3 ($f_s/f_d$)] $times 10^{-6}$ , where the first uncertainty is statistical, the second is systematic, and the third and fourth are due to uncertainties on the branching fraction of the normalization mode $B^0 to phi K_S^0$ and the ratio of hadronization fractions $f_s/f_d$. This is the most precise measurement of this branching fraction to date. Furthermore, a measurement of the branching fraction of the decay $B^0 to K_S^0 K_S^0$ is performed relative to that of the $B_s^0 to K_S^0 K_S^0$ channel, and is found to be $frac{BR(B^0 to K_S^0 K_S^0)}{BR(B_s^0 to K_S^0 K_S^0)}$ = [7.5 $pm$ 3.1 (stat) $pm$ 0.5 (syst) $pm$ 0.3 ($f_s/f_d$)] $times 10^{-2}$.
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.
Using a sample of $1.31 times 10^{9}$ $J/psi$ events collected with the BESIII detector at the BEPCII collider, we study the decays of $J/psi rightarrow K_S K_L$ and $K_S K_S$. The branching fraction of$J/psirightarrow K_S K_L$ is determined to be ${cal B}(J/psi rightarrow K_S K_L)=(1.93pm0.01~(rm{stat.})pm0.05~(rm{syst.}))times10^{-4}$, which significantly improves on previous measurements. No clear signal is observed for the $J/psi rightarrow K_S K_S$ process, and the upper limit at the 95% confidence level for its branching fraction is determined to be ${cal B}(J/psi rightarrow K_S K_S)<1.4times10^{-8}$, which improves on the previous searches by two orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.
The time-dependent CP asymmetry in B_s^0to J/psi K^+K^- decays is measured using $pp$ collision data at sqrt{s}=7TeV, corresponding to an integrated luminosity of 1.0fb^-1, collected with the LHCb detector. The decay time distribution is characterised by the decay widths Gamma_L and Gamma_H of the light and heavy mass eigenstates of the B_s^0--bar{B}_s^0 system and by a CP-violating phase phi_s. In a sample of 27,617 B_s^0to J/psi K^+K^- decays, where the dominant contribution comes from B_s^0to J/psiphi decays, these parameters are measured to be phi_s = 0.07 pm 0.09 (stat) pm 0.01 (syst) rad, Gamma_s equiv (Gamma_L+Gamma_H)/2 = 0.663 pm 0.005 (stat) pm 0.006 (syst) ps^-1, DeltaGamma_s equiv Gamma_L -Gamma_H = 0.100 pm 0.016 (stat) pm 0.003 (syst) & ps^-1, corresponding to the single most precise determination of phi_s, DeltaGamma_s and Gamma_s. The result of performing a combined analysis with B_s^{0} to J/psi pi^+pi^- decays gives phi_s = 0.01 pm 0.07 (stat) pm 0.01 (syst) rad, Gamma_s = 0.661 pm 0.004 (stat) pm 0.006 (syst) ps^-1, DeltaGamma_s = 0.106 pm 0.011 (stat) pm 0.007 (syst) & ps^-1. All measurements are in agreement with the Standard Model predictions.
A search for the decay $B^0_srightarrow J/psi K^{*0}$ with $K^{*0} rightarrow K^-pi^+$ is performed with 0.37 fb$^{-1}$ of $pp$ collisions at $sqrt{s}$ = 7 TeV collected by the LHCb experiment, finding a $Bs to Jpsi K^-pi^+$ peak of $114 pm 11$ signal events. The $K^-pi^+$ mass spectrum of the candidates in the $B^0_s$ peak is dominated by the $K^{*0}$ contribution. Subtracting the non-resonant $K^-pi^+$ component, the branching fraction of BsJpsiKst is $(4.4_{-0.4}^{+0.5} pm 0.8) times 10^{-5}$, where the first uncertainty is statistical and the second systematic. A fit to the angular distribution of the decay products yields the Kst polarization fractions $f_L = 0.50 pm 0.08 pm 0.02$ and $f_{||} = 0.19^{+0.10}_{-0.08} pm 0.02$.
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