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

This thesis presents the first study of the same-electric-charge $W^{\pm}W^{\pm}jj$ production using 20.3 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}=$ 8 TeV recorded by the ATLAS detector at the LHC during the year of 2012. Only the leptonic decays of both $W$'s are considered. Events are selected with two same-electric-charge leptons ($e^{\pm}e^{\pm}$, $e^{\pm}\mu^{\pm}$, $\mu^{\pm}\mu^{\pm}$) and at least two jets. The inclusive and electroweak productions of $W^{\pm}W^{\pm}jj$ are studied in two fiducial signal regions and the production cross sections are measured. First evidence for inclusive and electroweak production is observed with a significance of 4.5 and 3.6 standard deviations respectively. The measured cross sections are in agreement with the Standard Model predictions. First set of constraints on the anomalous $WWWW$ quartic gauge couplings are derived.