First evidence of $CP$ violation in beauty baryon to charmonium decays

Abstract

A study of the difference in the $CP$ asymmetries between $\hat{I}{›}_b^0\to J/\ddot{I}ˆp\ddot{I}{€}^{-}$ and $\hat{I}{›}_b^0\to J/\ddot{I}ˆp{K}^{-}$ decays, $\hat{I}”{\mathcal{A}}_{CP}$, is performed using proton-proton collision data collected by the LHCb experiment in the years 2015--2018, corresponding to an integrated luminosity of $6{\mathrm{fb}}^{-1}$. This quantity is measured to be $\hat{I}”{\mathcal{A}}_{CP}=(4.03\pm 1.18\pm 0.23)\%$, where the first uncertainty is statistical and the second is systematic. When combined with the previous LHCb result, a value of $\hat{I}”{\mathcal{A}}_{CP}=(4.31\pm 1.06\pm 0.28)\%$ is obtained, corresponding to a significance of $3.9\ddot{I}ƒ$ against the $CP$ symmetry hypothesis. Studies of triple-product asymmetries, which provide an additional probe of $CP$ violation, show no significant deviation from $CP$ symmetry.

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/3877/ (LHCb public pages)