Stop the Top Background of the Stop Search

TL;DR

This paper introduces new kinematic variables, especially M^W_T2, to better suppress Standard Model ttbar background in stop searches, significantly improving detection sensitivity at the LHC.

Contribution

The paper proposes novel kinematic variables with endpoint features to enhance stop signal detection and demonstrates their effectiveness with a 20-30% improvement in significance.

Findings

20%-30% improvement in discovery significance

Potential to exclude stop masses of 650-700 GeV at 8 TeV LHC

Most natural supersymmetric stop mass range can be probed

Abstract

The main background for the supersymmetric stop direct production search comes from Standard Model ttbar events. For the single-lepton search channel, we introduce a few kinematic variables to further suppress this background by focusing on its dileptonic and semileptonic topologies. All are defined to have end points in the background, but not signal distributions. They can substantially improve the stop signal significance and mass reach when combined with traditional kinematic variables such as the total missing transverse energy. Among them, our variable M^W_T2 has the best overall performance because it uses all available kinematic information, including the on-shell mass of both W's. We see 20%-30% improvement on the discovery significance and estimate that the 8 TeV LHC run with 20 fb-1 of data would be able to reach an exclusion limit of 650-700 GeV for direct stop production, as long as the stop decays dominantly to the top quark and a light stable neutralino. Most of the mass range required for the supersymmetric solution of the naturalness problem in the standard scenario can be covered.