Evidence for Electroweak Production of $W^{\pm }{W}^{\pm }jj$ in $pp$ Collisions at $\sqrt{s}=8$ TeV with the ATLAS Detector

This Letter presents the first study of $W^{\pm }{W}^{\pm }jj$, same-electric-charge diboson production in association with two jets, using 20.3 fb${}^{-1}$ of proton–proton collision data at $\sqrt{s}=8$ TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with two reconstructed same-charge leptons ($e^{\pm }{e}^{\pm }$, $e^{\pm }{\mu }^{\pm }$, and ${\mu }^{\pm }{\mu }^{\pm }$) and two or more jets are analyzed. Production cross sections are measured in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. First evidence for $W^{\pm }{W}^{\pm }jj$ production and electroweak-only $W^{\pm }{W}^{\pm }jj$ production is observed with a significance of $4.5$ and $3.6$ standard deviations respectively. The measured production cross sections are in agreement with Standard Model predictions. Limits at 95% confidence level are set on anomalous quartic gauge couplings.