Search for New Phenomena in Events with Four Charged Leptons
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We present two searches for new phenomena in events with four charged leptons, using data from pp collisions at s√=7\ TeV collected by the ATLAS detector corresponding to an integrated luminosity of 1.02 fb−1. The first search examines the four-lepton dataset for events that contain no identified Z→ℓ+ℓ− decays. Owing to the very low expected background, even a small number of such events would be of interest. After selection, 0.7+1.3−0.6(stat) +0.9−0.5(syst) events are expected from standard model backgrounds, and no events are observed. Using doubly-charged Higgs production as a benchmark model, upper limits are set on a fiducial cross-section for four-lepton production of 4.7 fb. A second search examines events with two identified Z→ℓ+ℓ− decays for evidence of resonant production of ZZ pairs via a massive graviton. For Mℓℓℓℓ>300 GeV, 1.9+1.0−0.1(stat) +0.8−0.1(syst) events are expected from standard model processes, and 3 events are observed. Limits are set on production of ZZ from high-mass sources, <0.9\ pb in the fiducial region at 95\% C.L. Using the Randall-Sundrum framework to quantify the result we report limits on σ(pp→G)×BF(G→ZZ) of 2.6-3.3\,pb, depending on the resonance mass. For a coupling of k/Mplˉ=0.1, the median expected 95\% C.L. lower limit on the mass of the graviton is MG>575 GeV, equal to the observed limit.
Run Conditions
7 TeV
1.02 fb-1 at 7 TeV