Phenomenology of the Minimal Scale Invariant Two-Higgs-Doublet Model

TL;DR

The paper analyzes a scale-invariant two-Higgs-doublet model (SI2HDM) where electroweak symmetry breaking is radiatively induced, generating the entire scalar spectrum at one loop in a Pure Radiative Higgs Mass (PRHM) scenario. Using a one-loop effective potential and a full set of theoretical and experimental constraints, the authors map a highly constrained viable parameter space in which the 125 GeV Higgs is the radiatively generated SM-like CP-even state. They find precise mass ranges (m_{H^{pm}}<130 GeV, m_{A^{0}} in (m_h/2, 600 GeV), m_{ta} in (185, 450 GeV)) and show that one-loop corrections suppress trilinear couplings and reduce di-Higgs production at the LHC by up to 45.5% relative to the SM, while EWPT remain in good agreement. These results yield distinctive, testable predictions for Higgs pair production and the extended scalar sector at the LHC and future colliders, offering a viable radiative path to addressing the hierarchy problem.

Abstract

We perform a comprehensive phenomenological analysis of the Scale Invariant Two Higgs Doublet Model (\textit{SI2HDM})~\cite{Lee:2012jn}. In this framework, the electroweak symmetry breaking is triggered radiatively, and the entire scalar mass spectrum, including that of the $125$ \textrm{GeV} Higgs boson, is generated at the one loop level. After imposing stringent theoretical and experimental constraints, a highly constrained viable parameter space is identified, where the SM-like Higgs mass is purely radiative. The model predicts substantial suppression in the triple Higgs couplings and the di-Higgs production cross section at the LHC13, which can be reduced by up to $45.5~\%$ compared to the Standard Model prediction.

Figures (6)

• Figure 1: Feynman diagrams contributing to di-Higgs production via gluon fusion. The left (right) diagram is referred to as the box (triangle) diagram in the literature, where $\varphi\equiv h,\eta$.
• Figure 2: Upper left panel: The squared CP-even mixing $s_{ev}^{2}$ versus the new CP-even scalar mass $m_{\eta}$ (in GeV), with the color palette indicating the difference in CP-even mixing. Upper right panel: The charged Higgs mass $m_{H^{\pm}}$ versus the CP-odd mass $m_{A^{0}}$ (both in GeV), with the color palette showing the new CP-even scalar mass $m_{\eta}$. The blue dashed horizontal line marks the experimental lower bound $m_{H^{\pm}}=78\,\textrm{GeV}$ALEPH:2013htx, and the vertical line corresponds to $m_{A^{0}}=m_{h}/2$. Lower left panel: The mixing parameter $t_{\beta}$ versus the charged Higgs mass $m_{H^{\pm}}$ (in GeV), with the color palette indicating the squared charged mixing $s_{ch}^{2}$. The red dashed line represents the experimental constraints from flavor physics that come from the decay $B_{d}^{0}\to\mu^{+}\mu^{-}$Enomoto:2015wbn. Lower right panel: The squared mixing $s_{od}^{2}$, $s_{ev}^{2}$ and $s_{ch}^{2}$ for each sector.
• Figure 3: Left panel: Normalized coupling strengths of the Higgs boson to gauge boson pairs $\kappa_{V}$ and fermions $\kappa_{F}$, with the color palette indicating the new CP-even scalar mass $m_{\eta}$ (in GeV). Right panel: Normalized coupling strengths of the new CP-even scalar to gauge boson pairs $\zeta_{V}$ and fermions $\zeta_{F}$, with the color palette indicating $m_{\eta}$ (in GeV).
• Figure 4: Left panel: The ratios $\delta_{\mathcal{O}}=(\mathcal{O}^{1-\ell}-\mathcal{O}^{\text{tree}})/\mathcal{O}^{\text{tree}}$ representing the relative mass difference for the CP-odd and charged sectors, with the color palette showing the mixing parameter $t_{\beta}$. Middle panel: The counter terms $\left|\delta\lambda_{45}/\lambda_{45}\right|$ versus $\left|\delta\lambda_{5}/\lambda_{5}\right|$, with the palette showing $\left|\delta\lambda_{345}/\lambda_{345}\right|$. Right panel: The differences in mixing angles $\Delta_{ev}=s_{ev}-s_{\beta}$, $\Delta_{ch}=s_{ch}-s_{\beta}$, and $\Delta_{od}=s_{od}-s_{\beta}$ for each sector.
• Figure 5: Left panel: Constraints from the oblique parameters $\Delta T$ and $\Delta S$, with the $68~\%$ (blue), $95~\%$ (green), and $99~\%$ (red) confidence ellipses from global electroweak fits. The color palette shows the chi-squared function $\chi_{\text{EWPT}}^{2}$. Right panel: The relative coupling differences $\delta_{\lambda_{hXX}}=(\lambda_{hXX}^{1-\ell}-\lambda_{hXX}^{\text{tree}})/\lambda_{hXX}^{\text{tree}}$ for $X\equiv h,A^{0},H^{\pm}$.