Status of the scalar singlet dark matter model

Area of Science:

• Particle Physics
• Cosmology
• Astrophysics

Background:

• The nature of dark matter remains one of the most significant unsolved problems in physics.
• A simple model for dark matter involves an additional neutral scalar particle stabilized by a symmetry.

Purpose of the Study:

• To perform global Bayesian and frequentist fits of the neutral scalar dark matter model.
• To identify viable parameter spaces for this dark matter model by combining various experimental constraints.

Main Methods:

• Utilized the GAMBIT (General Analysis of Minimal Beyond-Standard-Model Integrations and Tools) package.
• Employed four independent samplers for global model fitting.
• Varied singlet mass, coupling, and 13 nuisance parameters, including nuclear uncertainties and local dark matter density.

Main Results:

• Identified viable solutions for scalar singlet dark matter at couplings of order unity.
• Viable parameter spaces exist for singlet masses between the Higgs mass and ~300 GeV, and above ~1 TeV.
• The scalar singlet can constitute all dark matter for masses above ~1 TeV.
• A low-mass resonance region (~half Higgs mass) is viable under frequentist analysis but considered fine-tuned in Bayesian analysis.

Conclusions:

• The neutral scalar dark matter model remains viable across different mass ranges and experimental constraints.
• The high-mass region (>1 TeV) is a robust parameter space where the scalar singlet can be the sole dark matter candidate.
• While a low-mass resonance region is statistically viable, it presents fine-tuning challenges from a Bayesian perspective.