Current Status of Inert Higgs Dark Matter with Dark Fermions

TL;DR

This work proposes a minimal SM extension with a $Z_2$-odd singlet fermion, a $Z_2$-odd doublet fermion, and a $Z_2$-odd inert doublet scalar to address the muon $g-2$ anomaly, the $W$-boson mass discrepancy, and hints from Galactic Center γ-ray and AMS-02 antiproton observations. The authors perform a comprehensive parameter scan combining collider, relic-density, and direct-/indirect-detection constraints, deriving viable regions with a scalar DM mass in the $54$–$74$ GeV range (and heavier DM allowed under certain $m_W$ conditions); they show that HL-LHC and LZ will probe much of the parameter space, while a high-energy muon collider could access otherwise inaccessible neutral fermion states. The model predicts a compressed inert-scalar spectrum constrained by current LHC data, a small Higgs-portal coupling away from Higgs resonance, and potential DM annihilation channels that can explain the GC γ-ray excess and AMS-02 antiproton excess in limited regions. Overall, the study links EW precision, flavor, and DM phenomenology within a coherent framework, highlighting future experimental avenues—especially muon colliders—to test the scenario.

Abstract

The precision measurements of the muon magnetic moment and the $W$ boson mass have sparked interest in the potential deviations from standard model (SM) predictions. While it may be premature to attribute any excesses in these precision measurements to new physics, they do offer a valuable indication of potential directions for physics beyond the SM. Additionally, the particle nature of dark matter (DM) remains a crucial enigma. Despite the absence of any definitive DM signal in direct detection and collider experiments, the Galactic Center GeV $γ$-ray excess and the AMS-02 antiproton ($\overline{p}$) excess could potentially offer hints related to the evidence of DM. Motivated by these observations, we propose a simple DM model that addresses all these issues. This model extends the SM by incorporating singlet and doublet Dirac fermion fields, along with a doublet complex scalar field. For the viable parameter regions in this model, we find that future upgrades of the Large Hadron Collider and DM direct detection experiments can only partially probe them, while future high-energy muon colliders hold promise for exploring the unexplored parameter space.

Figures (11)

• Figure 1: The one-loop chirally enhanced Feynman diagram to the $\Delta a_{\mu}$ in this model.
• Figure 2: The contribution to $\Delta a_{\mu}$ in this model on the $(m_\Psi, m_{H^\pm})$ plane. We fixed $\Delta M_{\Psi\chi} = 100$ GeV, $|y_{H_1}| = 1$ and $|\kappa_M \times \kappa_\mu| = 0.5$. The sign of $y_{H_1}\kappa_M\kappa_\mu$ is fixed to be negative in the left panel while it is positive in the right panel. The solid blue, green, dotted blue and green represent the values of $\Delta a_{\mu}$ of $5\times 10^{-9}$, $10^{-9}$, $-10^{-9}$ and $-5\times 10^{-9}$, respectively. The dash-dotted black line indicates $\Delta a_{\mu} = 0$, where a complete cancellation between the two terms in the brackets of Eq. \ref{['eq:deltamu']} occurs. The orange band is the $1\sigma$ region favored to the discrepancy between the current experiment measurements and the SM results where the HVP is calculated using the data-driven method Aoyama:2020ynm. The light blue region is excluded by the LHC constraints.
• Figure 3: The Feynman diagrams for the one-loop $W$ boson mass corrections with the inert Higgs sector and new Dirac fermions.
• Figure 4: Contribution to $\Delta m_W$ from the $\Psi$ field projected onto the $(m_\Psi, |y_{H_1}|)$ plane. In the left panel, we fixed $\Delta M_{\Psi\chi} = 1$ GeV, while in the right panel, $\Delta M_{\Psi\chi} = 200$ GeV. The dotted red, dotted blue, solid blue and solid green lines represent the values of $\Delta m_{W}$ equal to $-50$ MeV, $-25$ MeV, $25$ MeV, and $75$ MeV, respectively. The dash-dotted black line indicates $\Delta m_{W} = 0.0$.
• Figure 5: The 95$\%$ C.L. regions on the panels of $m_s$ versus $\Delta^0$ (upper panels) and $\Delta^\pm$ (lower panels). The gray region favored by the data of $m_{W,\text{PDG}}$ and $\Delta a_\mu^\text{Lattice HVP}$. The red diamond region represents the combined results of $m_{W,\text{CDF II}}$ and $\Delta a_{\mu}^{e^+e^-\text{ HVP}}$. The green box indicates the region where the contribution to $m_{W,\text{CDF II}}$ satisfies $\Delta m^{H_2}_{W,\text{CDF II}} > \Delta m^\Psi_{W,\text{CDF II}}$, while the purple cross represents the region where $\Delta m^{H_2}_{W,\text{CDF II}} < \Delta m^\Psi_{W,\text{CDF II}}$. The solid black and dashed green lines in the upper right panel indicate the current limit from CMS and future probe from LHC Run 3, respectively.