Search for new physics in multi-body invariant masses in dijet events with an isolated lepton in pp collisions at sqrt(s)=13 TeV with the ATLAS detector

A search for resonances in events with at least one isolated charged lepton (electron or muon) is performed using 139 fb^-1 of sqrt(s)=13 TeV proton-proton collision data recorded by the ATLAS detector at the LHC. Deviations from Standard Model predictions are tested in three- and four-body invariant mass distributions constructed from jets and leptons. The study reports first model-independent limits on generic resonances characterized by cascade decays of particles leading to multiple jets and leptons in the final state. Model-independent limits are calculated using Gaussian shapes with different widths. The multi-body invariant masses are then used to set upper limits at a 95% confidence level on various beyond the standard model physics scenarios.