First measurement of the CP-violating phase in Bs0→J/ψ(→e+e-)ϕ decays

Abstract

A flavour-tagged time-dependent angular analysis of $B_s^0\to J/\psi \varphi$ decays is presented where the $J/\psi$ meson is reconstructed through its decay to an $e^{+}{e}^{-}$ pair. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and $8\text{,Te V}$, corresponding to an integrated luminosity of $3{\text{,fb}}^{-1}$. The $CP$-violating phase and lifetime parameters of the $B_s^0$ system are measured to be ${\varphi }_s=0.00\pm 0.28\pm 0.07\text{,rad}$, $\mathrm{\Delta }{\mathrm{\Gamma }}_s=0.115\pm 0.045\pm 0.011{\text{,ps}}^{-1}$ and ${\mathrm{\Gamma }}_s=0.608\pm 0.018\pm 0.012{\text{,ps}}^{-1}$ where the first uncertainty is statistical and the second systematic. This is the first time that $CP$-violating parameters are measured in the $B_s^0\to J/\psi \varphi$ decay with an $e^{+}{e}^{-}$ pair in the final state. The results are consistent with previous measurements in other channels and with the Standard Model predictions.