The 690 GeV scalar resonance

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 with a well-delimited mass $(M_{H})^{\textrm {Theor}} = 690\,\,(30)$ 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 represent 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 easily follows from basic properties of $\Phi ^{4}$ theories. Secondly, we spell out a definite experimental signature that characterises this resonance and is clearly visible in various LHC data.