Search for new non-resonant phenomena in high-mass dilepton nal states with the ATLAS detector

Abstract

A search for new physics with non-resonant signals in dielectron and dimuon nal states in the mass range above 2TeV is presented. This is the rst search for nonresonant signals in dilepton nal states at the LHC to use a background estimate from the data. The data, corresponding to an integrated luminosity of 139 fb�����1, were recorded by the ATLAS experiment in proton-proton collisions at a center-of-mass energy of ps = 13TeV during Run 2 of the Large Hadron Collider. The benchmark signal signature is a two-quark and two-lepton contact interaction, which would enhance the dilepton event rate at the TeV mass scale. To model the contribution from background processes a functional form is t to the dilepton invariant-mass spectra in data in a mass region below the region of interest. It is then extrapolated to a high-mass signal region to obtain the expected background there. No signi cant deviation from the expected background is observed in the data. Upper limits at 95% CL on the number of events and the visible cross-section times branching fraction for processes involving new physics are provided. Observed (expected) 95% CL lower limits on the contact interaction energy scale reach 35.8 (37.6)TeV.