Cosmological collider signals of modular spontaneous CP breaking

Abstract

We consider a modular-invariant extension of the Standard Model. Assuming that the modulus is the inflaton, the CP-violating phases of the Yukawa couplings evolve during inflation. This dynamics favours a Higgs condensate, so that Standard Model fermions mediate a one-loop cosmological collider signal enhanced by chemical potentials. The effect appears too small for next-generation experiments. We provide precise expressions for Dirac fermions with chemical potentials in de Sitter.

Comments: 21 pages, 3 figures. Webinar presentation of v1: https://youtu.be/ToUNLzRl8Pc v3: to appear on JHEP; we now compute rather than estimate the result, and it's smaller