Beyond Resonant Leptogenesis

by Apostolos Pilaftsis (University of Manchester)

Tuesday 28 Jul 2026, 11:30 → 12:30 Europe/Zurich

4/2-011 - TH common room (CERN)

The observed ultralight neutrinos may hold the key to understanding several puzzles in our Universe, including the origin of the Matter–AntiMatter Asymmetry and the nature of the Dark Matter. A natural explanation that accounts for the tiny neutrino masses is achieved by the famous seesaw mechanism that complements minimally the Standard Model of Particle Physics (SM) with the addition of singlet heavy neutrinos. First, I will briefly review how resonant mixing and decay of these heavy neutrinos can produce the observed Baryon Asymmetry in the Universe, through a mechanism now known as Resonant Leptogenesis (RL). Although successful RL is largely independent of the initial conditions of the early Universe, it requires a significant degree of degeneracy in the singlet neutrino masses in the absence of any extra flavour symmetries. Then, I will present a novel dominant mechanism for low-scale leptogenesis which becomes naturally enhanced by resonant thermal lepton-flavour coherences at two loops within the flavour-covariant Kadanoff-Baym formalism in the quasi-steady approximation. This mechanism works successfully for both Dirac and Majorana singlet neutrinos, and it does not rely on whether these singlet neutrinos are quasi-degenerate or not. It implies that successful low-scale leptogenesis can be comfortably realised with heavy neutrinos in the mass range between 1 GeV and 50 GeV.

My seminar will be based on my two recent works with Shaoping Li, https://arxiv.org/abs/2601.15921  and https://arxiv.org/abs/2604.06493 .