First observation of production of three massive gauge bosons

We present the search for heavy triboson production, specifically targeting the production of WWW, WWZ, WZZ and ZZZ processes in multileptonic final states with 137 fb^-1 of datacollected by the CMS detector during Run 2 of the LHC at sqrt(s) = 13 TeV. An event selection consisting of identically charged dileptons and trileptons is constructed to primarily study the WWW process, while the WWZ, WZZ and ZZZ processes are explored in four, five and six lepton final states. The analysis utilizes both traditional cut-based and multivariate techniques using boosted decision trees.