Split Dirac Supersymmetry: An Ultraviolet Completion of Higgsino Dark Matter

TL;DR

This paper introduces Split Dirac Supersymmetry, a model where gauginos have intermediate scale Dirac masses, maintaining gauge coupling unification and providing testable predictions for Higgsino dark matter and collider signals.

Contribution

It presents a novel UV-complete framework for split supersymmetry with Dirac gauginos, preserving gauge unification and naturally explaining the Higgsino dark matter candidate.

Findings

Gauge coupling unification is maintained at a higher scale.

Higgsino dark matter properties are naturally generated from UV dynamics.

Distinct collider signatures arise from R-parity violating decays.

Abstract

Motivated by the observation that the Higgs quartic coupling runs to zero at an intermediate scale, we propose a new framework for models of split supersymmetry, in which gauginos acquire intermediate scale Dirac masses of $\sim 10^{8-11}$ GeV. Scalar masses arise from one-loop finite contributions as well as direct gravity-mediated contributions. Like split supersymmetry, one Higgs doublet is fine-tuned to be light. The scale at which the Dirac gauginos are introduced to make the Higgs quartic zero is the same as is necessary for gauge coupling unification. Thus, gauge coupling unification persists (nontrivially, due to adjoint multiplets), though with a somewhat higher unification scale $\gtrsim 10^{17}$ GeV. The $\mu$-term is naturally at the weak scale, and provides an opportunity for experimental verification. We present two manifestations of Split Dirac Supersymmetry. In the "Pure Dirac" model, the lightest Higgsino must decay through R-parity violating couplings, leading to an array of interesting signals in colliders. In the "Hypercharge Impure" model, the bino acquires a Majorana mass that is one-loop suppressed compared with the Dirac gluino and wino. This leads to weak scale Higgsino dark matter whose overall mass scale, as well as the mass splitting between the neutral components, is naturally generated from the same UV dynamics. We outline the challenges to discovering pseudo-Dirac Higgsino dark matter in collider and dark matter detection experiments.