A Search for First Generation Leptoquarks in $\sqrt{s}$ = 7 TeV pp Collisions with the ATLAS Detector

The Standard Model is an incomplete theory of nature. Numerous extensions of the Standard Model predict the existence of leptoquarks (LQ), color-triplet bosons which carry both baryon and lepton number. This dissertation presents the results of a search for pair production of first generation scalar leptoquarks in the $e\MET jj$ final state. The search is performed in $pp$ collisions corresponding to an integrated luminosity of $1.03~\mathrm{fb}^{-1}$, at a center-of-mass energy $\sqrt{s}=7$~TeV, recorded with the ATLAS detector at the LHC. A multivariate discriminant is used to distinguish signal-like events from background-like events. Observations are consistent with expectations from Standard Model backgrounds, thus limits on allowed LQ mass are determined. First generation scalar leptoquarks with mass $m_{LQ}<$~558~GeV are excluded at a 95\% confidence level for $\beta\equiv BR(LQ\rightarrow eq)=0.5$. When combined with a complimentary search in the $eejj$ final state, leptoquarks with mass $m_{LQ}<$~607~(660)~GeV are excluded for $\beta=0.5$~(1.0). These are the strongest limits in existence.