A top-squark hunter's guide

TL;DR

This paper explores the expected mass range and decay signatures of top squarks in natural supersymmetry models, emphasizing that they may be heavier than previously thought and proposing more theory-aligned search strategies for the LHC.

Contribution

It provides a detailed analysis of top squark mass ranges and decay modes consistent with naturalness, and introduces a semi-simplified model for improved LHC search strategies.

Findings

Top squarks may lie in the 0.5-3 TeV range, heavier than prior expectations.

Decay modes include roughly equal probabilities for t1->bW1 and Z_{1,2}.

LHC signatures include tar{t}+ ot{E}_T, tar{b}+ ot{E}_T, and bar{b}+ ot{E}_T.

Abstract

In supersymmetric models with radiatively-driven naturalness and light higgsinos, the top squarks may lie in the 0.5- 3TeV range and thus only a fraction of natural parameter space is accessible to LHC searches. We outline the range of top squark and lightest SUSY particle masses preferred by electroweak naturalness in the standard parameter space plane. We note that the branching fraction for b-> s\gamma decay favors top squarks much heavier than 500 GeV. Such a range of top-squark mass values is in contrast to previous expectations where m(stop)<500 GeV had been considered natural. In radiative natural SUSY, top squarks decay roughly equally via t1-> bW1 and Z_{1,2} where W1 and Z_{1,2} are higgsino-like electroweak-inos. Thus, top squark pair production should yield all of t\bar{t}+\eslt, t\bar{b}+\eslt, b\bar{t}+\eslt and b\bar{b}+\eslt signatures at comparable rates. We propose that future LHC top squark searches take place within a semi-simplified model which corresponds more closely to expectations from theory.