First observation of production of three massive gauge bosons

We present the search for heavy triboson production, specifically targeting the production of WWW , WW Z , W Z Z and Z Z Z processes in multileptonic final states with 137 fb−1 of data collected by the CMS detector during Run 2 of the LHC at √ s = 13TeV. An event selection consisting of identically charged dileptons and trileptons is constructed to primarily study the WWW process, while the WW Z , W Z Z and Z Z Z 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.