IFIC Seminar: Diraxiogenesis

by Maximilian Berbig (IFIC, Valencia)

Tuesday 20 Feb 2024, 12:00 → 13:30 Europe/Madrid

1001-Primera-1-1-1 - Paterna. Seminario (Universe)

The family of Dirac Seesaw models offers an intriguing alternative explanation for the smallness of neutrino masses without necessarily requiring microscopic lepton number violation. We review the basics of both Majorana and Dirac Seesaws and argue that in models employing global symmetries there should be a Goldstone boson associated with Dirac neutrino mass generation - similar to the more well known Majoron - which we call the Diraxion. Following the Affleck-Dine approach we demonstrate how a rotation of the scalar condensate in the Diraxion direction can be induced after  inflation from the same higher dimensional operator responsible for the Diraxion mass. This background field can play the role of an effective chemical potential for the right handed neutrinos à la spontaneous Baryogenesis. Together with the Dirac-Weinberg operator this allows for a self-contained Dirac-Leptogenesis version of the recently proposed Lepto-Axiogenesis scenario explaining the observed Baryon asymmetry. The Diraxion rotation can also explain the dark matter relic abundance via the kinetic misalignment mechanism and a subleading fraction could be detectable in cosmic neutrino background searches via decays to neutrinos. Explaining only the baryon asymmetry on the other hand can lead to an amount of right handed neutrino dark radiation, which is potentially observable with CMB-S4. A key ingredient of all Axiogenesis scenarios is the dynamics of relatively light scalar called the Saxion, that in our case has a mass at the GeV-scale and which might reveal itself in heavy meson decays at LHCb. We elaborate on the strong constraints arising from Saxion isocurvature perturbations, requiring the absence of parametric resonance (which would source too warm dark matter) and Saxion thermalization.
 

Diraxiogenesis_Talk-2.pdf