Search for Supersymmetry in events with a displaced vertex and a muon

This talk presents a search for long-lived particles giving rise to displaced decays with at least one muon. The analysis selects events that pass a muon or missing-transverse-momentum trigger and contain a displaced muon and a displaced vertex with at least three tracks and a vertex visible invariant mass of at least 20 GeV. The analyzed dataset of proton--proton collisions at $\sqrt{s} =$ 13 TeV was collected with the ATLAS detector and corresponds to 136 fb$^{-1}$. Observed event yields are compatible with those expected from background processes. Results are interpreted as exclusion limits on scenarios with pair-production of long-lived top squarks that decay via a small $R$-parity-violating coupling to a quark and a muon. Top squarks up to 1.8 TeV are excluded for a lifetime of 0.1 ns.