Search for resonances in multi-body invariant masses in events with an isolated lepton using 139 $fb^{-1}$ of $\sqrt{s} = 13$ TeV \textit{pp} collisions collected by the ATLAS detector

A search for resonances in events with at least one isolated charged lepton (e or μ) is performed using 139fb−1 of √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 a range of new physics scenarios implemented in Monte Carlo simulations.