How to avoid unnatural hierarchical thermal leptogenesis

Abstract

A one-flavour naturalness argument suggests that the Type I seesaw model cannot naturally explain neutrino masses and the baryon asymmetry of the Universe via hierarchical thermal leptogenesis. We prove that there is no way to avoid this conclusion in a minimal three-flavour setup. We then comment on the simplest ways out. In particular, we focus on a resolution utilising a second Higgs doublet. Such models predict an automatically SM-like Higgs boson, (maximally) TeV-scale scalar states, and low- to intermediate-scale hierarchical leptogenesis with $10^3\text{ GeV}\lesssim M_{N_1}\lesssim 10^7\text{ GeV}$.

10 pages, 2 figures, submitted to Proceedings of the 18th International Conference From the Planck Scale to the Electroweak Scale (2015)

References in corpus (10)

• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of summer 2016
• Updated NNLO QCD predictions for the weak radiative B-meson decays
• Search for neutral MSSM Higgs bosons decaying to a pair of tau leptons in pp collisions
• Search for neutral Higgs bosons of the minimal supersymmetric standard model in pp collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector
• Flavoured leptogenesis: a successful thermal leptogenesis with N_1 mass below 10^8 GeV
• The importance of N2 leptogenesis
• Global fits of the two-loop renormalized Two-Higgs-Doublet model with soft $Z_2$ breaking
• Electroweak naturalness in three-flavour Type I see-saw and implications for leptogenesis
• Natural leptogenesis and neutrino masses with two Higgs doublets
• Naturalness redux