Higgs doublet decay as the origin of the baryon asymmetry
  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).
