Benjamin Kaplan

An excess of events over the Standard Model predictions in final states with three or more high momentum charged leptons would constitute evidence of new physical processes. Presented is a generic search for new phenomena in such events. To reduce the largest Standard Model backgrounds, events consistent with the production of a Z boson are rejected. Events are selected from 1.02 fb$^{-1}$ of proton-proton collision data recorded by the ATLAS detector at $\sqrt{s}$ = 7 TeV. There is no requirement on missing energy or jet activity. A total of 25.9 $\pm$ 3.8(stat) $\pm$ 4.3(syst) events are expected in the signal region from Standard Model sources, and 31 events are observed. In a second signal region, which uses a tighter lepton momentum selection criteria, 4.9 $\pm$ 1.6(stat) $\pm$ 0.9(syst) are expected from Standard Model processes, and 6 events are observed. The observed p-values for consistency with the Standard Model expectation are 27\% and 33\% in the two signal regions. A model of the pair production of doubly-charged Higgs bosons is used as a benchmark for determining fiducial limits. The observed fiducial cross-section limits are 38 fb and 14 fb in the two signal regions. Cross-section upper limits at 95\% confidence are also set at 41 (34) fb for the pair production of 200 (300) GeV excited electron neutrinos.