Search for long-lived charginos based on a disappearing-track signature in pp collisions at √s = 13TeV with the ATLAS detector

Abstract

This paper presents a search for direct electroweak gaugino or gluino pair production with a chargino nearly mass-degenerate with a stable neutralino. It is based on an integrated luminosity of 36.1 fb-1 of pp collisions at √s = 13TeV collected by the ATLAS experiment at the LHC. The final state of interest is a disappearing track accompanied by at least one jet with high transverse momentum from initial-state radiation or by four jets from the gluino decay chain. The use of short track segments reconstructed from the innermost tracking layers signi_cantly improves the sensitivity to short chargino lifetimes. The results are found to be consistent with Standard Model predictions. Exclusion limits are set at 95% con_dence level on the mass of charginos and gluinos for di_erent chargino lifetimes. For a pure wino with a lifetime of about 0.2 ns, chargino masses up to 460 GeV are excluded. For the strong production channel, gluino masses up to 1.65TeV are excluded assuming a chargino mass of 460 GeV and lifetime of 0.2 ns.