Search for new phenomena in a lepton plus high jet multiplicity final state with the ATLAS experiment using √s = 13 TeV proton-proton collision data

Abstract

A search for new phenomena in final states characterized by high jet multiplicity, an isolated lepton (electron or muon) and either zero or at least three b-tagged jets is presented. The search uses 36.1 fb-1 of √s = 13TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. The dominant sources of background are estimated using parameterized extrapolations, based on observables at medium jet multiplicity, to predict the b-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. No signi cant excess over the Standard Model expectation is observed and 95% con fidence-level limits are extracted constraining four simpli ed models of R-parity-violating supersymmetry that feature either gluino or top-squark pair production. The exclusion limits reach as high as 2.1 TeV in gluino mass and 1.2TeV in top-squark mass in the models considered. In addition, an upper limit is set on the cross-section for Standard Model t¯tt¯t production of 60 fb (6.5 x the Standard Model prediction) at 95% con dence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields.