Search for direct chargino production in anomaly-mediated supersymmetry breaking scenarios based on a disappearing-track signature in pp collisions at sqrt(s)=8 TeV with the ATLAS detector

A search is presented for direct chargino production in anomaly-mediated supersymmetry breaking scenarios using 20.3 fb−1 of pp collisions at sqrt(s) = 8 TeV collected with the ATLAS experiment at the LHC. In AMSB models, the lightest chargino is nearly mass-degenerate with the lightest neutralino and its lifetime is long enough to be detected in the tracking detectors by identifying decays that result in tracks with no associated hits in the outer region of the tracking system. No significant excess beyond the background expectation is observed for candidate tracks with large transverse momentum, and constraints on chargino properties are obtained. In the AMSB scenarios, a chargino mass below 270 GeV is excluded at 95% confidence level, extending sensitivity beyond the LEP experiments for the first time.