On the ATLAS Top Mass Measurements and the Potential for Stealth Stop Contamination

TL;DR

This paper examines how stealth stop decays can bias top mass measurements at the LHC, highlighting the need to consider such contamination for accurate top mass and stop searches.

Contribution

It identifies potential biases in top mass measurements caused by stealth stop contamination and proposes strategies to improve the template method's robustness.

Findings

Stealth stop decays can bias top mass measurements by up to 2.0 GeV.

Current top mass uncertainties are comparable to the bias introduced by stealth stops.

A simple strategy is proposed to enhance the template method for semi-leptonic channels.

Abstract

The discovery of the stop - the Supersymmetric partner of the top quark - is a key goal of the physics program enabled by the Large Hadron Collider. Although much of the accessible parameter space has already been probed, all current searches assume the top mass is known. This is relevant for the "stealth stop" regime, which is characterized by decay kinematics that force the final state top quark off its mass shell; such decays would contaminate the top mass measurements. We investigate the resulting bias imparted to the template method based ATLAS approach. A careful recasting of these results shows that effect can be as large as 2.0 GeV, comparable to the current quoted uncertainty on the top mass. Thus, a robust exploration of the stealth stop splinter requires the simultaneous consideration of the impact on the top mass. Additionally, we explore the robustness of the template technique, and point out a simple strategy for improving the methodology implemented for the semi-leptonic channel.