First measurement of time-dependent $CP$ violation in the flavor-changing neutral-current decay $B^0\to K_S^0\hat{I}{¼}^{+}\hat{I}{¼}^{-}$

Abstract

A flavor-tagged time-dependent analysis of $B^0\to K_S^0\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ decays is performed across the full dimuon mass range excluding the $J/\ddot{I}ˆ$ and $\ddot{I}ˆ(2S)$ resonance regions. The analysis uses proton-proton collision data collected by the LHCb experiment in 2011--2018 at center-of-mass energies of 7, 8 and 13TeV, corresponding to an integrated luminosity of 9$f{b}^{-1}$. The CP violation parameters are determined to be $C=-0.13\pm 0.32\pm 0.04$ and $S=+0.82\pm 0.29\pm 0.05$, where the first uncertainties are statistical and the second are systematic. The results are consistent with the Standard Model prediction. This is the first experimental study of time-dependent CP violation in $b\to s{l}^{+}{l}^{-}$ processes.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/3477/ (LHCb public pages)