Search for squarks and gluinos in pp collisions at s=13 TeV and 13.6 TeV in events with τ-leptons, jets and missing transverse momentum using the ATLAS detector

A search for R-parity-conserving supersymmetry in events with large missing transverse momentum, jets and at least one hadronically decaying τ-lepton is presented. Both gluino and squark pair production are considered, with the cascade decay of each gluino or squark producing either a τ-slepton or a τ-sneutrino. Three channels are examined, requiring either exactly one hadronically decaying τ-lepton and no other leptons, exactly one hadronically decaying τ-lepton and at least one other lepton, or two or more hadronically decaying τ-leptons. Analyses in the three channels are optimised independently and combined statistically. Two separate analysis strategies, either a cut-and-count or machine-learning approach, are used. The search uses 140 fb-1 and 51.8 fb-1 of pp collision data recorded by the ATLAS detector at the Large Hadron Collider during 2015–2018 at s=13 TeV and 2022–2023 at s=13.6 TeV, respectively. Gluino masses below 2.25 TeV and squark masses up to 1.7 TeV