Observation of the 𝐽/𝜓→𝜇+⁢𝜇−⁢𝜇+⁢𝜇− decay in proton-proton collisions at √𝑠=13 TeV

Abstract

The 𝐽/𝜓→𝜇+⁢𝜇−⁢𝜇+⁢𝜇− decay has been observed with a statistical significance in excess of five standard deviations. The analysis is based on an event sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of 33.6 fb−1. Normalizing to the 𝐽/𝜓→𝜇+⁢𝜇− decay mode leads to a branching fraction of [10.1+3.3−2.7⁢(stat)±0.4⁢(syst)]×10−7, a value that is consistent with the standard model prediction.