MeV-scale Seesaw and Leptogenesis

Domcke, Valerie Fiona; Drewes, Marco; Hufnagel, Marco; Lucente, Michele

Preprint

PUBDB-2020-03620

MeV-scale Seesaw and Leptogenesis

Domcke, V. F. (Corresponding author)DESY* ; Drewes, M. ; Hufnagel, M.DESY* ; Lucente, M.

2020

[10.3204/PUBDB-2020-03620]

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Please use a persistent id in citations: doi:10.3204/PUBDB-2020-03620

Report No.: CERN-TH-2020-158; DESY-20-159; arXiv:2009.11678

Abstract: We study the type-I seesaw model with three right-handed neutrinos and Majorana masses below the pion mass. In this mass range, the model parameter space is not only strongly constrained by the requirement to explain the light neutrino masses, but also by experimental searches and cosmological considerations. In the existing literature, three disjoint regions of potentially viable parameter space have been identified. In one of them, all heavy neutrinos decay shortly before big bang nucleosynthesis. In the other two regions, one of the heavy neutrinos either decays between BBN and the CMB decoupling or is quasi-stable. We show that previously unaccounted constraints from photodisintegration of nuclei practically rule out all relevant decays that happen between BBN and the CMB decoupling. Quite remarkably, if all heavy neutrinos decay before BBN, the baryon asymmetry of the universe can be quite generically explained by low-scale leptogenesis, i.e. without further tuning in addition to what is needed to avoid experimental and cosmological constraints. This motivates searches for heavy neutrinos in pion decay experiments.

Keyword(s): nucleosynthesis: big bang ; neutrino: heavy: decay ; cosmic background radiation: decoupling ; neutrino: heavy ; neutrino: decay ; neutrino: mass ; neutrino: heavy: search for ; neutrino: right-handed ; pi: decay ; pi: mass ; mass: Majorana ; baryon: asymmetry ; leptogenesis ; seesaw model ; nucleus