Search for anomaly-mediated supersymmetry breaking with the ATLAS detector based on a disappearing-track signature in pp collisions at sqrt(s) = 7 TeV

TL;DR

This study searches for long-lived charginos predicted by anomaly-mediated supersymmetry breaking models in 7 TeV proton-proton collisions, using disappearing-track signatures in the ATLAS detector, and sets limits on their mass and lifetime.

Contribution

It presents the first search for AMSB charginos with disappearing tracks at 7 TeV, establishing new constraints on their mass and lifetime parameters.

Findings

No excess over Standard Model background observed.

Charginos with mass below 92 GeV and lifetime 0.5-2 ns are excluded.

Constraints improve previous limits on AMSB models.

Abstract

In models of anomaly-mediated supersymmetry breaking (AMSB), the lightest chargino is predicted to have a lifetime long enough to be detected in collider experiments. This letter explores AMSB scenarios in pp collisions at sqrt(s) = 7 TeV by attempting to identify decaying charginos which result in tracks that appear to have few associated hits in the outer region of the tracking system. The search was based on data corresponding to an integrated luminosity of 1.02 fb^-1 collected with the ATLAS detector in 2011. The pT spectrum of candidate tracks is found to be consistent with the expectation from Standard Model background processes and constraints on the lifetime and the production cross section were obtained. In the minimal AMSB framework with m_3/2 < 32 TeV, m_0 < 1.5 TeV, tan(beta) = 5 and mu > 0, a chargino having mass below 92 GeV and a lifetime between 0.5 ns and 2 ns is excluded at 95% confidence level.