Higgs Portal to New Physics

The Standard Model with an added Higgs portal interaction and no explicit mass terms is a classically scale-invariant theory. In this case the scale of electroweak symmetry breaking can be induced radiatively by the Coleman-Weinberg mechanism operational in a hidden sector, and then transmitted to the Standard Model through the Higgs portal. The smallness of the generated values for the Higgs vev and mass, compared to the UV cutoff is naturally explained by this mechanism.  We analyse the phenomenology of such a model in the context of present and future colliders and low energy measurements. We then show how these classically scale-invariant models can generate the baryon asymmetry of the Universe via a leptogenesis mechanism without the need of introducing mass scales by hand or their resonant fine-tuning. Finally, when Higgs portal interactions of the theory include an additional singlet which is non-minimally coupled to gravity, this generates a single-field slow-roll inflation mechanism. No large threshold corrections appear in our approach to inflation, which is robust up to Planck scales, so that the electroweak scale and the SM Higgs mass are not affected. The singlet field responsible for inflation also gives a viable dark matter candidate in this approach.

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