Unified interpretation of 95 GeV di-photon and di-tau Excesses in the Georgi-Machacek Model

TL;DR

This work tests whether the Georgi–Machacek model can coherently explain the 95 GeV hints observed in the di-photon and di-tau channels with a single light CP-even custodial singlet $H$. By employing a one-loop renormalization-group–improved effective potential and positive-definiteness vacuum-stability conditions, along with perturbative unitarity, electroweak precision data, $B$-physics, and Higgs observables, the authors identify a narrow viable region in which charged-scalar loops enhance $H\to\gamma\gamma$ while fermionic rescaling controls $H\to\tau\tau$, yielding signal strengths compatible at about $2\sigma$. The viable parameter space features distinct patterns in singlet mixing and the triplet VEV $v_\Delta$, with a mass hierarchy among custodial multiplets that can be probed by HL-LHC and future lepton colliders through precision $\kappa_V$ tests and direct searches for exotic scalars. The study provides concrete predictions for upcoming experiments and highlights the potential of RG-improved stability criteria to expand viable regions in extended Higgs sectors.

Abstract

We revisit the 95 GeV excesses in the $γγ$ and $ττ$ channels in the Georgi-Machacek model, where a single light $CP$-even custodial singlet $H$ can account for both hints. Using one-loop renormalization group-improved effective potential and positive-definiteness conditions for vacuum stability, together with perturbative unitarity, electroweak precision tests, $B$-physics, and Higgs data, we identify a narrow but viable parameter region. In this region, charged and doubly charged scalars enhance $H\toγγ$, while the fermionic rescaling controls $H\toττ$, yielding combined signal strengths compatible at the $2σ$ level. The scenario predicts characteristic patterns in the singlet mixing and triplet VEV and is highly testable at the HL-LHC and future lepton colliders via precision $κ_V$ measurements and direct exotic searches.

Figures (3)

• Figure 1: Scan samples under successive constraints in the ($\mu_{\gamma\gamma}$, $\mu_{\tau\tau}$) panel with color coded by $\chi^2_{\rm 95}$. The left panel applies perturbative unitarity, the positive-definiteness vacuum-stability conditions, and passes the HiggsBounds/HiggsSignals tests. The right panel additionally imposes constraints from $B$-physics, the oblique parameters $(S,T,U)$, and the Higgs $\kappa$ fits.
• Figure 2: Similar to Fig. \ref{['fig:muchi2']}: Top panel shows the ($\kappa_{ff}$, $\kappa_{VV}$) plane, with color indicating the $p$-value as calculated by HiggsSignals. The middle panel displays the ($\alpha$, $\mathcal{B}(B\to X_s \gamma)$) plane, with color representing $\mathcal{B}(B_s^0\to \mu^+ \mu^-)$. The bottom panel presents the distributions of the oblique parameters $S$, $T$, and $U$.
• Figure 3: Similar to Fig. \ref{['fig:muchi2']}: Top panel shows the ($m_H, v_{\Delta}$) plane, with color indicating the $p_{\text{value}}$; bottom panel shows the ($m_{h}, m_{H_5}$) plane, with color representing $m_{H_3}$.