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.