Observation of $WWW$ Production in $pp$ Collisions at $\sqrt{s} = 13$ TeV with the ATLAS Detector

TL;DR

This paper reports the first observation of WWW production in proton-proton collisions at 13 TeV, measuring its cross section with high significance and comparing it to theoretical predictions.

Contribution

It presents the first observation of WWW production at the LHC with a significance of 8.0 sigma and measures its cross section using advanced multivariate analysis techniques.

Findings

WWW production observed with 8.0 sigma significance

Measured cross section of 820 ± 100 (stat) ± 80 (syst) fb

Result is approximately 2.6 sigma above the Standard Model prediction

Abstract

This Letter reports the observation of $WWW$ production and a measurement of its cross section using 139 fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from $WWW$ production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive $WWW$ production cross section is measured to be $820 \pm 100\,\text{(stat)} \pm 80\,\text{(syst)}$ fb, approximately 2.6 standard deviations from the predicted cross section of $511 \pm 18$ fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy.