Cosmological non-Gaussianity from the neutrino seesaw mechanism

Le résumé fourni par la source

The neutrino mass generation via conventional seesaw mechanism is realized at high scales around O ( 10 14 ) GeV with natural Yukawa couplings of O ( 1 ) , making the test of the neutrino seesaw a great challenge. It is intriguing to note that the neutrino seesaw scale is typically around the upper range of the cosmological inflation scale. In this work, we propose a new framework incorporating inflation and the neutrino seesaw in which the inflaton primarily decays into right-handed neutrinos after inflation. This decay process is governed by the inflaton interaction with the right-handed neutrinos that respects the shift symmetry. Through the neutrino seesaw mechanism, fluctuations of the Higgs field can modulate the inflaton decays and contribute to the curvature perturbation. We investigate the induced non-Gaussian signatures and demonstrate, for the first time, that such signatures provide an important means to directly probe the high scale of natural neutrino seesaw. We further analyze the interplay of the non-Gaussianity signatures with the low-energy neutrino experiments, and their interplay with the Higgs self-coupling measurements at the LHC and future colliders.

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