Measurement of the effective Bs0→J/ψKS0 lifetime

This paper reports the first measurement of the effective Bs0→J/ψKS0 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: τJ/ψKS0eff=1.75±0.12(stat)±0.07(syst) ps and B(Bs0→J/ψKS0)=(1.97±0.23)×10−5. For the latter measurement, the uncertainty includes both statistical and systematic sources.