Controlling the fine-tuning problem with singlet scalar dark matter

TL;DR

This paper proposes a minimal extension to the Standard Model with singlet scalars and vector-like fermions to address the Higgs mass hierarchy problem, dark matter viability, and predict Landau poles, considering experimental constraints.

Contribution

It introduces a minimal scalar and fermion extension that alleviates fine-tuning, predicts Landau poles, and remains consistent with collider and dark matter experiments.

Findings

Singlet scalars can serve as dark matter candidates.

The model predicts Landau poles depending on the number of singlets.

Minimal extensions are sufficient to address fine-tuning and experimental constraints.

Abstract

Assuming that no other conventional new physics is found immediately at the LHC, we investigate how just the consistent solution of the scalar mass hierarchy problem points towards the minimal necessary field content. We show that to ameliorate the fine-tuning problem, one needs to introduce more scalar degrees of freedom. The simplest solution is one or more real singlets (with the possibility of combining two of them in a complex singlet), which may act as viable cold dark matter candidates, because the constraints on the scalar potential disfavor any mixing between the new scalar(s) with the SM doublet. Furthermore, the fine-tuning problem of the new scalars necessitates the introduction of vector-like fermions. Thus, singlet scalar(s) and vector fermions are minimal enhancements over the Standard Model to alleviate the fine-tuning problem. We also show that the model predicts Landau poles for all the scalar couplings, whose positions depend only on the number of such singlets. Thus, introduction of some new physics at that scale becomes inevitable. We also discuss how the model confronts the LHC constraints and the latest XENON100 data.