Emergence of the Electroweak Scale through the Higgs Portal

TL;DR

The paper addresses how to naturally generate the electroweak scale by embedding Coleman–Weinberg radiative symmetry breaking in a scale-invariant SM extended with a hidden CW sector, communicating the generated scale to the SM through a Higgs portal. The mechanism yields two vevs and a two-scalar spectrum with a small Higgs–hidden-Higgs mixing, allowing a 125 GeV Higgs while decoupling the SM vector-boson masses from the CW dynamics. The authors argue for vanishing renormalised masses at the origin as a natural starting point, supported by dimensional regularisation and UV fixed-point perspectives, and they analyze a rich phenomenology with current experimental constraints and clear discovery avenues at HL-LHC and future linear colliders. Overall, the scenario offers a minimal, testable step toward radiatively generating the electroweak scale, while not fully solving the hierarchy problem but providing a concrete framework for exploring scale-generation mechanisms.

Abstract

Having discovered a candidate for the final piece of the Standard Model, the Higgs boson, the question remains why its vacuum expectation value and its mass are so much smaller than the Planck scale (or any other high scale of new physics). One elegant solution was provided by Coleman and Weinberg, where all mass scales are generated from dimensionless coupling constants via dimensional transmutation. However, the original Coleman-Weinberg scenario predicts a Higgs mass which is too light; it is parametrically suppressed compared to the mass of the vectors bosons, and hence is much lighter than the observed value. In this paper we argue that a mass scale, generated via the Coleman-Weinberg mechanism in a hidden sector and then transmitted to the Standard Model through a Higgs portal, can naturally explain the smallness of the electroweak scale compared to the UV cutoff scale, and at the same time be consistent with the observed value. We analyse the phenomenology of such a model in the context of present and future colliders and low energy measurements.

Figures (2)

• Figure 1: Ratio of $\lambda_{\phi}/e^{4}_{\phi}$ at $\Lambda_{\rm UV}$ required to generate a hierarchy of $\Lambda_{\rm UV}/\langle\phi\rangle=10^{16},10^{15},10^{14}$ (from top to bottom) as a function of the gauge coupling $e_{\phi}$.
• Figure 2: Scatter plot of the model described in Sec. \ref{['Phenomenology']} for $10^5$ randomly generated parameter choices in the $(\lambda_{\rm{P}},m_{h_2})$ plane. Points below the black dash-dotted line require some fine-tuning according to Eqs. \ref{['massmin1']}, \ref{['massmin']}. The region excluded by current LHC measurements is shown in red. The cyan region can be probed by LHC with high luminosity and the orange region shows a projection for a combination of a high luminosity LHC with a linear collider. Light blue indicates constraints from stellar evolution. The constraints on the parameter space for a Landau pole separation of 4, and 16 orders of magnitude are included in yellow and light green, respectively. The remaining allowed parameter points are depicted in green.