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 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 Φ 4 theories. Secondly, we spell out a definite experimental signature that characterises this resonance and is clearly visible in various LHC data.