pMSSM versus complete models and the excellent prospects for top-squark discovery at HL-LHC

TL;DR

This paper critically examines the limitations of simplified models in LHC sparticle searches, advocates for the more comprehensive NUHM4 model, and highlights the promising prospects for top-squark discovery at the HL-LHC within natural supersymmetry scenarios.

Contribution

It introduces a more realistic NUHM4 model for supersymmetry searches and discusses the potential for near-complete exploration of natural parameter space at HL-LHC.

Findings

Top-squarks in the 1-2 TeV range are accessible at HL-LHC.

Simplified models can misrepresent the true parameter space.

Natural solutions often involve heavy first/second generation sfermions.

Abstract

LHC sparticle search limits are usually performed within the context of simplified models and subsequently interpreted within the 19 parameter phenomenological MSSM (pMSSM) as to how many models avoid search limits for a particular sparticle mass, often including WIMP dark matter constraints. We provide a critical discussion of this procedure and how it can go wrong due to the introduction of new prejudices. By ameliorating these conditions, one is pushed into the more plausible four extra parameter non-universal Higgs model (NUHM4). Implementing a decoupling/quasi-degeneracy solution to the SUSY flavor and CP problems leads to first/second generation sfermions in the tens-of-TeV range. In this case, the natural solutions typically contain top-squarks in the 1-2 TeV range which are accessible to high-lumi LHC (HL-LHC) searches. This search channel, along with higgsino and wino pair production, may allow a nearly complete scan of natural/plausible parameter space by HL-LHC.