First evidence of violation in beauty baryon to charmonium decays

A study of the difference in theasymmetries betweenanddecays,, is performed using proton-proton collision data collected by the LHCb experiment in the years 2015–2018, corresponding to an integrated luminosity of. This quantity is measured to be, where the first uncertainty is statistical and the second is systematic. When combined with the previous LHCb result, a value ofis obtained, corresponding to a significance ofagainst thesymmetry hypothesis. Studies of triple-product asymmetries, which provide an additional probe ofviolation, show no significant deviation fromsymmetry.