The 690 GeV scalar resonance

TL;DR

The paper addresses the origin of spontaneous symmetry breaking and the potential metastability of the Higgs vacuum in perturbation theory, proposing a non-perturbative second scalar resonance with $(M_H)^{\rm Theor} = 690(30)$ GeV that stabilizes the potential. It derives a two-mass structure from basic $\Phi^4$ theory using Gaussian Effective Action and lattice insights, yielding a heavy, relatively narrow state with $\kappa_\lambda \approx 5.5$ and a production mechanism dominated by gluon-gluon fusion. The authors test the scenario against LHC data, identifying hints of an excess/defect pattern in multi-lepton final states around 680–710 GeV that could be consistent with a resonance at $M_H \approx 690$ GeV and a total width of $\sim 20$–$30$ GeV; they stress the need for dedicated searches that exploit interference patterns rather than simple bump hunting. If confirmed, this would indicate a non-perturbative scalar sector underlying SSB and provide a concrete path toward vacuum stability with a large ultraviolet cutoff.

Abstract

Spontaneous symmetry breaking through the Higgs field has been experimentally confirmed as a basic ingredient of the Standard Model. However, the origin of the phenomenon may not be entirely clear, because, in perturbation theory, the vacuum turns out to be a metastable state. An alternative scenario was proposed that implies a second resonance of the Higgs field ${\cal H}$ with a well delimited mass $(M_H)^{\rm Theor} = 690\,(30)$ GeV. This stabilises the potential, but, owing to an $H$ coupling to longitudinal $W$s with the same typical strength as that of the low-mass state with $m_h= 125$ GeV, it would still remain a relatively narrow resonance. Our scope here is twofold. First, leaving out many details, we outline a simple logical path where the, apparently surprising, idea of such a second resonance follows from basic properties of $Φ^4$ theories. Secondly, we spell out a definite experimental signature of this resonance that is clearly visible in various LHC data. As a by-product, the ${\cal H} ^3$ term gives $κ_λ= (M_H/m_h) \sim $ 5.5 consistently with the ATLAS and CMS data.

Figures (6)

• Figure 1: A picture illustrating the role of the ZPE in a first-order scenario of SSB. Differently from the standard second-order picture, this has to compensate for a tree-level potential with no non-trivial minimum.
• Figure 2: The average differential cross section measured by ATLAS atlasnew, in bins of increasing size, and the difference of measured and background cross sections as reported in table \ref{['leptonxsection']}.
• Figure 3: The dominant ATLAS ggF-low 4-lepton events atlas4lHEPData in bins of 60 GeV from 530 to 830 GeV. The integrated luminosity is 139 fb$^{-1}$ and the average acceptance is 0.38. The red curve is the fit with eq. (\ref{['sigmat']}) and the dashed blue curve is the background.
• Figure 4: The CMS 4-lepton data CMS_4leptons_2024 for $S/B$ at E= 640$\div$740 GeV and our fit with eq. (\ref{['sigmat']}).
• Figure 5: The CMS 4-lepton data CMS_4leptons_2024 for the $S/B$ ratio from 600 to 800 GeV, as well as several curves for $M_H=692$ GeV and four different widths. Note the two empty bins at 750 and 795 GeV, which put the upper limits at $S/B<0.66$ and $S/B<0.86$, respectively.