The real singlet scalar dark matter model

TL;DR

This work analyzes the real singlet scalar dark matter model with a $Z_2$ symmetry, scanning the DM mass $m_D$, Higgs mass $m_h$, and Higgs-portal coupling $\\lambda$ to reproduce the observed relic density. By incorporating Breit–Wigner resonance effects, it connects the relic-density constraint to predictions for direct detection cross sections $\\sigma_n^{SI}$, indirect signals via $\\langle \\sigma v \\rangle_0$, and Higgs-portal collider signatures including $h\\rightarrow SS$ decays. The study finds that current direct and indirect searches exclude two regions in parameter space, while the resonance region yields suppressed signals but remains testable with future experiments; BR$_{visible}$ typically remains sizable, offering promising LHC observables through invisible Higgs decays. Overall, the paper demonstrates how a minimal Higgs-portal DM model can be tightly constrained by a combination of relic density, direct/indirect detection, and collider data, highlighting the importance of resonance effects in shaping the viable parameter space.

Abstract

We present an undated comprehensive analysis for the simplest dark matter model in which a real singlet scalar with a $Z_2$ symmetry is introduced to extend the standard model. According to the observed dark matter abundance, we predict the dark matter direct and indirect detection cross sections for the whole parameter space. The Breit-Wigner resonance effect has been considered to calculate the thermally averaged annihilation cross section. It is found that three regions can be excluded by the current direct and indirect dark matter search experiments. In addition, we also discuss the implication of this model for the Higgs searches at colliders.

Figures (4)

• Figure 1: The predicted coupling $\lambda$ as a function of the DM mass $m_D$ from the observed DM abundance for the $m_h =120$ GeV and $m_h =180$ GeV cases. The dashed line denotes the constant $\langle \sigma v \rangle$ case when its value is taken at the usual freeze-out temperature $x=20$.
• Figure 2: The predicted DM-nucleon scattering cross section $\sigma_{n}^{SI}$ for the whole parameter space. The short dotted lines with arrowhead indicate the excluded regions from the DM direct search experiments CDMS II and XENON10. The region among two dashed lines ($162 \; {\rm GeV}< m_h < 166$ GeV) can be excluded by the Tevatron experiments CDF and D0. Two purple short dashed lines describe the minimum $m_D$ allowed by both the DM observed abundance and the vacuum stability/pertubativity for $\lambda_S = 10^{-3}$ and $\lambda_S = 0.4$. The right panel corresponds to two fixed Higgs mass cases with current and future experimental upper bounds.
• Figure 3: The predicted thermally averaged DM annihilation cross section $\langle \sigma v \rangle_0$. The right panel corresponds to two fixed Higgs mass cases.
• Figure 4: The predicted branching ratio of the Higgs visible decay ${\rm BR_{visible}}$. The right panel corresponds to two fixed Higgs mass cases.