Speakers
Description
A search for the production of three massive vector bosons in $pp$ collisions
is performed using data at $\sqrt{s} = 13$ TeV recorded with the ATLAS detector
at the Large Hadron Collider in the years 2015--2017, corresponding to an
integrated luminosity of $79.8$ fb$^{-1}$. Events with two same-sign leptons
$\ell$ (electrons or muons) and at least two reconstructed jets are selected to
search for $WWW \to \ell \nu \ell \nu qq$. Events with three leptons without
any same-flavour opposite-sign lepton pairs are used to search for $WWW \to
\ell \nu \ell\nu \ell \nu$, while events with three leptons and at least one
such lepton pair and one or more reconstructed jets are used to search for $WWZ
\to \ell \nu qq \ell \ell$. Finally, events with four leptons are analysed to
search for $WWZ \to \ell \nu \ell \nu \ell \ell$ and $WZZ \to qq \ell \ell \ell
\ell$. Evidence for the joint production of three massive vector bosons in
$pp$ collisions is observed with a significance of 4.0 standard
deviations, where the expectation is 3.1.
