Observation of the L0b --> J/ps X- K+ decay

Abstract

Using proton-proton collision data corresponding to an integrated luminosity of 140 fb-1 collected by the CMS experiment at vs = 13 TeV, the L0b --> J/ps X- K+ decay is observed for the first time, with a statistical significance exceeding 5 standard deviations. The relative branching fraction, with respect to the L0b --> ps(2S) L decay, is measured to be (v(Lub --> J/psx-K+)/v(Lub --> ps (2S) L) = [3.38 ± 1.02 ± 0.61 ± 0.03]%, where the first uncertainty is statistical, the second is systematic, and the third is related to the uncertainties in v(ps(2S) --> J/ps p+ p-) and v(X- --> Lp-).