Measurement of Effective $$B_{s}^{0} \to J{\text{/}}\psi K_{S}^{0}$$ Lifetime Using Run-II CMS Data

The effective lifetime for the decay $$B_{s}^{0} \to J{\text{/}}\psi K_{S}^{0}$$ is reported using the data from pp collision at centre of mass energy $$\sqrt s $$ = 13 TeV recorded by CMS experiment at the LHC during 2016, 2017 and 2018. The data sample corresponds to an integrated luminosity of 140 fb–1. The measurement uses the two-dimensional unbinned maximum likelihood (UML) fit to B-invariant mass and the decay time to extract the observable. Effective lifetime is measured as 1.59 $$ \pm $$ 0.07(stat) $$ \pm $$ 0.03(syst) ps, which is in good agreement with the standard model prediction and stands as the most precise result to date.