Evidence for the production of three massive vector bosons in pp collisions with the ATLAS detector

Abstract

A search for the production of three massive vector bosons in proton-proton collisions is performed using data at √s = 13TeV recorded with the ATLAS detector at the Large Hadron Collider in the years 2015-2017, corresponding to an integrated luminosity of 79.8fb−1. Events with two same-sign leptons ` (electrons or muons) and at least two reconstructed jets are selected to search for W±W±W∓ → `ν`νqq. Events with three leptons without any same-flavour opposite-sign lepton pairs are used to search for W±W±W∓ → `ν`ν`ν, while events with three leptons and at least one same-flavour opposite-sign lepton pair and one or more reconstructed jets are used to search for W±W∓Z → `νqq``. Finally, events with four leptons are analysed to search for W±W∓Z → `ν`ν`` and W±ZZ → qq````. Evidence for the joint production of three massive vector bosons is observed with a significance of 4.0 standard deviations, where the Standard Model expectation is 3.1 standard deviations.