Probing EWSB Naturalness in Unified SUSY Models with Dark Matter

TL;DR

This study analyzes electroweak symmetry breaking fine-tuning in unified SUSY models, showing current dark matter detection experiments probe less fine-tuned regions, with future experiments increasingly constraining more fine-tuned models.

Contribution

It provides a detailed assessment of EWSB fine-tuning in CMSSM and NUHM models in relation to dark matter detection prospects, highlighting the impact of mass hierarchies and relic density constraints.

Findings

Current experiments probe less fine-tuned models

Future experiments will target more fine-tuned parameter regions

Mass hierarchies influence neutralino annihilation channels

Abstract

We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the context of two unified Supersymmetry scenarios: the Constrained Minimal Supersymmetric Model (CMSSM) and models with Non-Universal Higgs Masses (NUHM), in light of current and upcoming direct detection dark matter experiments. We consider both those models that satisfy a one-sided bound on the relic density of neutralinos, $\Omega_{\chi} h^2 < 0.12$, and also the subset that satisfy the two-sided bound in which the relic density is within the 2 sigma best fit of WMAP7 + BAO + H0 data. We find that current direct detection searches for dark matter probe the least fine-tuned regions of parameter-space, or equivalently those of lowest Higgs mass parameter $\mu$, and will tend to probe progressively more and more fine-tuned models, though the trend is more pronounced in the CMSSM than in the NUHM. Additionally, we examine several subsets of model points, categorized by common mass hierarchies; $M_{\chi_0} \sim M_{\chi^\pm}, M_{\chi_0} \sim M_{\stau}, M_{\chi_0} \sim M_{\stop_1}$, the light and heavy Higgs poles, and any additional models classified as "other"; the relevance of these mass hierarchies is their connection to the preferred neutralino annihilation channel that determines the relic abundance. For each of these subsets of models we investigated the degree of fine-tuning and discoverability in current and next generation direct detection experiments.