Using a data sample of proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of , the and decays are observed with significances exceeding 5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to and , where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of and mesons, .
© The Author(s) 2022.