A Minimally Fine-Tuned Supersymmetric Standard Model

TL;DR

The paper tackles the electroweak fine-tuning problem in supersymmetry by proposing a framework with low-scale SUSY breaking mediated by SM gauge interactions and an extended Higgs sector containing a singlet $S$. It presents a concrete 5D warped-space model in which the DSB sector and boundary conditions yield calculable, nonunified soft masses and a Higgs potential that supports viable EWSB with modest tuning ($\Delta^{-1}\approx 20\%$). A pedestrian sector provides a stable dark-matter candidate, and neutralino phenomenology is analyzed, showing compatibility with current constraints for certain parameter choices. A purely 4D realization is also outlined, demonstrating that similar tuning reductions can be achieved without extra dimensions. Overall, the work preserves gauge coupling unification, flavor universality, and introduces a testable, less-tuned SUSY paradigm with distinctive Higgs-sector and dark-matter features.

Abstract

We construct supersymmetric theories in which the correct scale for electroweak symmetry breaking is obtained without significant fine-tuning. We calculate the fine-tuning parameter for these theories to be at the 20% level, which is significantly better than in conventional supersymmetry breaking scenarios. Supersymmetry breaking occurs at a low scale of order 100 TeV, and is transmitted to the supersymmetric standard-model sector through standard-model gauge interactions. The Higgs sector contains two Higgs doublets and a singlet field, with a superpotential that takes the most general form allowed by gauge invariance. An explicit model is constructed in 5D warped space with supersymmetry broken on the infrared brane. We perform a detailed analysis of electroweak symmetry breaking for this model, and demonstrate that the fine-tuning is in fact reduced. A new candidate for dark matter is also proposed, which arises from the extended Higgs sector of the model. Finally, we discuss a purely 4D theory which may also significantly reduce fine-tuning.

Figures (4)

• Figure 1: The basic structure of our framework.
• Figure 2: The diagrams inducing (a) $F_S$, (b) $S$, (c) $F_S^\dagger S$, and (d) $|S|^2$ terms in the Lagrangian. The crosses on internal lines represent insertions of supersymmetry-breaking masses.
• Figure 3: The 5D picture of our theory.
• Figure 4: Schematic description for the evolution of the gauge couplings in our theory.