Title: Minimal signatures of the Standard Model in cosmological collider physics
Abstract: The detection of an oscillating pattern in the bispectrum of density perturbations would imply the presence of heavy particles at a scale close to the Hubble rate during inflation. A minimal scenario providing this signature only requires a coupling of SM particles to the inflaton. We focus on the fermions, whose dispersion relation can be modified by the coupling to the inflaton, leading to an enhanced particle production even if their mass during inflation is larger than the Hubble scale. We study two particularly interesting cases. The detection of the simultaneous contributions of two SM fermions to the bispectrum would allow us to conclude that the Higgs field during inflation resided in a second minimum of its potential located at high scales. Another remarkable possibility is that the Higgs vacuum during inflation is dynamically set by the contribution of the fermion density to the Higgs potential. This one-parameter model offers a very minimal and predictive signature detectable in cosmological collider physics.