(Light) Stop Signs

TL;DR

This paper proposes search strategies for light stop squarks near the top quark mass, emphasizing the use of spin correlations and rapidity differences to distinguish signals from Standard Model backgrounds.

Contribution

It introduces novel analysis techniques utilizing spin correlations and rapidity differences to improve bounds on light stop squarks in challenging mass regions.

Findings

Spin correlation can exclude a 200 GeV stop at 95% CL with 20 fb^-1 at 8 TeV LHC.

Rapidity difference Delta y(t,tbar) is sensitive to stop presence.

Systematic uncertainties in top production are a major challenge.

Abstract

Stop squarks with a mass just above the top's and which decay to a nearly massless LSP are difficult to probe because of the large SM di-top background. Here we discuss search strategies which could be used to set more stringent bounds in this difficult region. In particular, we note that both the rapidity difference Delta y(t,tbar) and spin correlations (inferred from, for example, Delta phi(l+,l-)) are sensitive to the presence of stops. We emphasize that systematic uncertainties in top quark production can confound analyses looking for stops, making theoretical and experimental progress on the understanding of Standard Model top production at high precision a very important task. We estimate that spin correlation alone, which is relatively robust against such systematic uncertainties, can exclude a 200 GeV stop at 95% confidence with 20 fb^-1 at the 8 TeV LHC.