Abstract
We minimally extend the Standard Model (SM) with a ${\mathrm{Z}}_{2}$ symmetric potential containing a single scalar field, serving as our inflaton with a quartic self-coupling. In the model we have symmetry breaking in both sectors, and with the addition of an inflaton-Higgs portal, the universe is able to efficiently reheat via 2-2 inflaton-Higgs scattering. Assuming that the universe with a positive cosmological constant should be metastable, only one particular symmetry breaking pattern in the vacuum is possible, without the need to finely tune the Higgs quartic self-coupling. Inflatons with masses in the range $O({10}^{\ensuremath{-}3})\ensuremath{\le}{m}_{\ensuremath{\chi}}\ensuremath{\le}{m}_{h}$ and mixing angles that span ${\ensuremath{\theta}}_{m}^{2}=O({10}^{\ensuremath{-}11}--{10}^{\ensuremath{-}2})$ evade all current cosmological, experimental, and stability constraints required for a metastable electroweak vacuum. Upgraded particle physics experiments may be able to probe the parameter space with ${\ensuremath{\theta}}_{m}^{2}\ensuremath{\ge}O({10}^{\ensuremath{-}4})$, where we would observe trilinear Higgs couplings suppressed by up to 2% compared to the SM value. However, to access the parameter space of very weakly coupled inflatons, we rely on the proposals to build experiments that target the hidden sector.
Highlights
The Standard Model (SM) is in excellent agreement with the experimental data at the present time
The central measured values for the top and Higgs boson masses correspond to the situation of a metastable electroweak (EW) vacuum [1,2,3,4]
The experimental indication of the metastability of the EW vacuum is especially interesting in view of the theoretical expectations of the inconsistency of eternal de Sitter expansion of the universe, which would correspond to the present day dark energy domination [10,11]
Summary
The Standard Model (SM) is in excellent agreement with the experimental data at the present time. During inflation the Higgs direction is stabilized by its positive mass generated by the interaction with the inflaton field [12,13], while at a late time the contribution of the inflaton is negligible, and the EW vacuum becomes metastable. By demanding that we have successful preheating with a reheating temperature at least above the EW phase transition, which is required for the generation of baryon asymmetry from leptogenesis, we arrive to a rather tightly constrained region of parameters for the inflaton field. This region will be largely explored by current and planned experiments on the high intensity frontier.
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