Is natural higgsino-only dark matter excluded?

TL;DR

This paper examines whether natural higgsino-only dark matter models are compatible with current experimental constraints, concluding that such models with non-thermal relic density augmentation are essentially excluded by direct and indirect detection limits.

Contribution

It provides a comprehensive analysis of natural SUSY models with higgsino-like neutralinos against current detection constraints, highlighting their exclusion.

Findings

Natural higgsino-like neutralinos have a thermal relic abundance below observed dark matter levels.

Non-thermal production mechanisms cannot reconcile higgsino-only models with current detection limits.

Current experiments strongly constrain or exclude natural higgsino-only dark matter scenarios.

Abstract

The requirement of electroweak naturalness in supersymmetric (SUSY) models of particle physics necessitates light higgsinos not too far from the weak scale characterized by m(weak)~ m(W,Z,h)~100 GeV. On the other hand, LHC Higgs mass measurements and sparticle mass limits point to a SUSY breaking scale in the multi-TeV regime. Under such conditions, the lightest SUSY particle is expected to be a mainly higgsino-like neutralino with non-negligible gaugino components (required by naturalness). The computed thermal WIMP abundance in natural SUSY models is then found to be typically a factor 5-20 below its measured value. To gain concordance with observations, either an additional DM particle (the axion is a well-motivated possibility) must be present or additional non-thermal mechanisms must augment the neutralino abundance. We compare present direct and indirect WIMP detection limits to three natural SUSY models based on gravity-, anomaly- and mirage-mediation. We show that the case of natural higgsino-only dark matter where non-thermal production mechanisms augment its relic density, is essentially excluded by a combination of direct detection constraints from PandaX-II, LUX and Xenon-1t experiments, and by bounds from Fermi-LAT/MAGIC observations of gamma rays from dwarf spheroidal galaxies.