Minimal Gaugino Mediation

TL;DR

Minimal Gaugino Mediation (Mg̃M) addresses the SUSY flavor and CP problems by enforcing a boundary condition at the compactification scale where gaugino masses are nonzero while all scalar soft terms vanish. The approach relies on an extra-dimensional setup in which gauge fields propagate in the bulk and communicate SUSY breaking from a hidden brane to the MSSM matter brane, with radiative RG running above the GUT scale playing a crucial role. The authors provide an explicit model combining higher-dimensional SUSY breaking with a novel shining mechanism to generate a μ term of the same order as the gaugino masses, and they show that the resulting sparticle spectrum is predictive and largely bino-like LSP phenomenology with viable dark matter density. The framework remains compatible with gauge coupling unification, yields testable predictions for the superpartner spectrum, and offers a new extra-dimensional solution to the μ problem that avoids the usual Bμ problem and SUSY CP violation beyond Yukawa phases.

Abstract

We propose Minimal Gaugino Mediation as the simplest known solution to the supersymmetric flavor and CP problems. The framework predicts a very minimal structure for the soft parameters at ultra-high energies: gaugino masses are unified and non-vanishing whereas all other soft supersymmetry breaking parameters vanish. We show that this boundary condition naturally arises from a small extra dimension and present a complete model which includes a new extra-dimensional solution to the mu problem. We briefly discuss the predicted superpartner spectrum as a function of the two parameters of the model. The commonly ignored renormalization group evolution above the GUT scale is crucial to the viability of Minimal Gaugino Mediation but does not introduce new model dependence.

Figures (4)

• Figure 1: The dependence of the masses of the stau, the lightest neutralino and the lightest Higgs on the compactification scale for fixed $M_{1/2}=250$ GeV. The neutralino mass ($104$ GeV) and the Higgs mass ($111$ GeV) are almost independent of the compactification scale and the GUT gauge group. The rising solid line and the dashed line indicate the mass of the stau in $SU(5)$ and $SO(10)$, respectively.
• Figure 2: The allowed region of the parameter space for Mg̃M with $SU(5)$ and $SO(10)$ unified group. The curves at the bottom of the figure correspond to LEP II limits on the masses of the Higgs (more restrictive) and stau (less restrictive). Demanding that relic LSPs contribute the cosmologically preferred amount of cold dark matter and do not over-close the universe singles out the region of parameter space between the lines labeled $\Omega h^2 = 0.1$ and $0.3$.
• Figure 3: Left graph: particle masses as functions of $M_{1/2}$ for fixed compactification scale. The lines correspond to (from lightest to heaviest at $M_{1/2}=600$ GeV) the lightest Higgs, lightest neutralino, right-handed stau, second lightest neutralino, heavy chargino, pseudoscalar Higgs, left-handed stop, and gluino. Right graph: contours of constant $\tan \beta$. The contours correspond to $\tan \beta$ of 9, 12, 15, 18, and 21 from left to right. The solid lines are for $SU(5)$, the dashed ones for $SO(10)$.
• Figure 4: A brane configuration which leads to the Minimal Gaugino Mediation boundary condition. Pictured is the extra dimension from left to right with periodic boundary conditions. We also show the exponentially decaying vacuum expectation values of $\phi$ and $\phi^c$ which are responsible for generating hierarchically small supersymmetry breaking and the $\mu$ term.