Higgs doublet decay as the origin of the baryon asymmetry

TL;DR

This paper introduces a novel leptogenesis mechanism via Higgs doublet decay in the standard seesaw model, allowing successful baryon asymmetry generation at low RH neutrino masses without complex flavor effects.

Contribution

It demonstrates that Higgs doublet decays can produce the baryon asymmetry efficiently at low scales, establishing a new leptogenesis pathway independent of flavor effects.

Findings

Leptogenesis can occur from Higgs decay at RH neutrino masses above 2 GeV.

The mechanism is effective even if RH neutrinos are not thermalized.

Scenario is testable through direct RH neutrino production.

Abstract

We consider a question which curiously had not been properly considered so far: in the standard seesaw model what is the minimum value the mass of a right-handed (RH) neutrino must have for allowing successful leptogenesis via CP-violating decays? To answer this question requires to take into account a number of thermal effects. We show that, for low RH neutrino masses and thanks to these effects, leptogenesis turns out to proceed efficiently from the decay of the Standard Model (SM) scalar doublet components into a RH neutrino and a lepton. Such decays produce the asymmetry at low temperatures, slightly before sphaleron decoupling. If the RH neutrino has thermalized prior from producing the asymmetry, this mechanism turns out to lead to the bound $m_N>2$ GeV. If, instead, the RH neutrinos have not thermalized, leptogenesis from these decays is enhanced further and can be easily successful, even at lower scales. This Higgs-decay leptogenesis new mechanism works without requiring an interplay of flavor effects and/or cancellations of large Yukawa couplings in the neutrino mass matrix. Last but not least, such a scenario turns out to be testable, from direct production of the RH neutrino(s).