Stop on Top: SUSY Parameter Regions, Fine-Tuning Constraints

TL;DR

This paper investigates the parameter space of minimal supersymmetric models to identify regions compatible with LHC data, Higgs mass constraints, and naturalness, highlighting the role of gaugino sectors in reducing fine-tuning.

Contribution

It provides a detailed scan of supersymmetric models showing how gaugino sector adjustments can lower fine-tuning in the stop-on-top scenario.

Findings

CMSSM requires at least 10^4 fine-tuning.

Nonuniversal Higgs masses also require about 10^4 fine-tuning.

Gaugino sector modifications can reduce fine-tuning to around 100.

Abstract

We analyze minimal supersymmetric models in order to determine in what parameter regions with what amount of fine-tuning they are capable of accomodating the LHC-allowed top-stop degeneracy window. The stops must be light enough to enable Higgs naturalness yet heavy enough to induce a 125 GeV Higgs boson mass. These two constraints imply a large mass splitting. By an elaborate scan of the parameter space, we show that stop-on-top scenario requires at least Delta_CMSSM ~ O(10^4) fine-tuning in the CMSSM. By relaxing the CMSSM parameter space with nonuniversal Higgs masses, we find that Delta_NUHM1 ~ O(10^4). The CMSSM with gravitino LSP works slightly better than the NUHM1 model. Compared to all these, the CMSSM with mu<0 and nonuniversal gauginos yield a much smaller fine-tuning Delta_{mu,g} ~ O(100). Our results show that gaugino sector can pave the road towards a more natural stop-on-top scenario.