Second resonance of the Higgs field: motivations, experimental signals, unitarity constraints

Abstract

Perturbative calculations predict that the Standard Model (SM) effective potential should have a new minimum, well beyond the Planck scale, much deeper than the electroweak vacuum. As it is not obvious that gravitational effects can get so strong to stabilize the potential, most authors have accepted the metastability scenario in a cosmological perspective. This perspective is needed to explain why the theory remains trapped into our electroweak vacuum, but requires to control the properties of matter in the extreme conditions of the early universe. Alternatively, one can consider the completely different idea of a non-perturbative effective potential which, as at the beginning of the SM, is restricted to the pure ${\Phi }^4$ sector yet consistent with the now existing analytical and numerical studies. In this approach, where the electroweak vacuum is the lowest-energy state, besides the resonance of mass $m_h=125$ GeV defined by the quadratic shape of the potential at its minimum, the Higgs field should exhibit a second resonance with mass $690\pm 10(\mathrm{stat})\pm 20(\mathrm{sys})$ GeV associated with the zero-point energy determining the potential depth. Despite its large mass, this would couple to longitudinal $W$s with the same typical strength as the low-mass state at 125 GeV and represent a relatively narrow resonance of width ${\Gamma }_H=30÷38$ GeV, mainly produced at LHC by gluon-gluon fusion. So it is interesting that, in the LHC data, one can find various indications for a new resonance in the expected mass range with a non-negligible statistical significance. As this could become an important new discovery by just adding two missing samples of RUN2 data, we outline further refinements of the theoretical predictions that could be obtained by implementing unitarity constraints, in the presence of fermion and gauge fields, with coupled-channel calculations used for meson spectroscopy.

Plain LaTeX, 36 pages, 12 figures, 4 tables; v2: plain two-column LaTeX, 13 figures, 7 tables, more discussion of theory and of experimental data; v3: final version accepted for publication in European Physical Journal C, with additional analysis and discussion

References in corpus (13)

• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• A low-lying scalar meson nonet in a unitarized meson model
• Cosmological implications of the Higgs mass measurement
• Critical behaviour of the Ising model on the 4-dimensional lattice
• On gravitational and thermal corrections to vacuum decay
• Observation of four-top-quark production in the multilepton final state with the ATLAS detector
• Non-vanishing boundary effects and quasi-first order phase transitions in high dimensional Ising models
• First search for exclusive diphoton production at high mass with tagged protons in proton-proton collisions at $\sqrt{s}=$ 13 TeV
• An alternative heavy Higgs mass limit
• The mass scales of the Higgs field
• Experimental signals for a second resonance of the Higgs field
• A hidden, heavier resonance of the Higgs field
• Revising the universality class of the four-dimensional Ising model

Cited by in corpus (1)

• The 690 GeV scalar resonance