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

TL;DR

This paper reports the first measurement of decay-time-dependent CP asymmetries in the decay $B_s^0 ightarrow J/ ho K_{ m S}^0$ and updates the ratio of branching fractions, using data from the LHCb detector at 7 and 8 TeV.

Contribution

It provides the first measurement of CP asymmetries in $B_s^0 ightarrow J/ ho K_{ m S}^0$ decay and an updated ratio of branching fractions, utilizing 3.0 fb$^{-1}$ of LHCb data.

Findings

Measured CP asymmetries with large uncertainties.

Determined the branching fraction ratio to be approximately 0.0431.

Results are consistent with Standard Model expectations.

Abstract

The first measurement of decay-time-dependent CP asymmetries in the decay $B_s^0\rightarrow J/\psi K_{\rm S}^0$ and an updated measurement of the ratio of branching fractions $\mathcal{B}(B_s^0\rightarrow J/\psi K_{\rm S}^0)/\mathcal{B}(B_d^0\rightarrow J/\psi K_{\rm S}^0)$} 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 $A_{\Delta\Gamma}(B_s^0\rightarrow J/\psi K_{\rm S}^0) = 0.49_{-0.65}^{+0.77}(stat) \pm 0.06(syst)$, $C_{\rm dir}(B_s^0\rightarrow J/\psi K_{\rm S}^0) = -0.28 \pm 0.41(stat) \pm 0.08(syst)$ and $S_{\rm mix}(B_s^0\rightarrow J/\psi K_{\rm S}^0) = -0.08 \pm 0.40(stat) \pm 0.08(syst)$. The ratio $\mathcal{B}(B_s^0\rightarrow J/\psi K_{\rm S}^0)/\mathcal{B}(B_d^0\rightarrow J/\psi K_{\rm S}^0)$ 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.