Hunting Asymmetric Stops

TL;DR

This paper introduces a novel stop search strategy for natural SUSY at the LHC, focusing on asymmetric decay modes and a new variable called topness to improve background suppression and detection sensitivity.

Contribution

It proposes a new asymmetric stop decay channel search and introduces the topness variable to enhance background rejection in stop searches.

Findings

Asymmetric decay modes can significantly reduce traditional stop search sensitivity.

The topness variable effectively suppresses top background in stop searches.

The proposed methods improve detection prospects for natural stops at the LHC.

Abstract

We point out that in the irreducible natural SUSY spectrum, stops have comparable branching fractions to chargino-bottom and neutralino-top in the vast bulk of parameter space, provided only that both decay modes are kinematically accessible. The total stop pair branching fractions into ttbar + MET can therefore be reduced to O(50%), while b bbar + X branching fractions are typically much smaller, O(10%), thus limiting the reach of traditional stop searches. We propose a new stop search targeting the asymmetric final state \~t\~t* --> t chi^0 b chi^pm, which can restore sensitivity to natural stops in the 7 and 8 TeV LHC runs. In addition we present a new variable, topness, which efficiently suppresses the dominant top backgrounds to semi-leptonic top partner searches. We demonstrate the utility of topness in both our asymmetric search channel and traditional \~t\~t* --> ttbar + MET searches and show that it matches or out-performs existing variables.