Speaker
Dr
enrico bertuzzo
(Scuola Normale Superiore)
Description
We discuss the conditions to realize a scenario of ‘strong thermal leptogenesis’,
where the final asymmetry is fully independent of the initial conditions, taking into
account both heavy and light neutrino flavor effects. In particular, the contribution
to the final asymmetry from an initial pre-existing asymmetry has to be negligible.
We show that in the case of a hierarchical right-handed (RH) neutrino mass spectrum, the only possible way is a N2 -dominated leptogenesis scenario with a lightest
RH neutrino mass M1 <<
10^9 GeV and with a next-to-lightest RH neutrino mass
10^12 GeV >> M2 >> 10^9 GeV. This scenario necessarily requires the presence of a
heaviest third RH neutrino specie. Moreover, we show that the final asymmetry has
to be dominantly produced in the tauon flavour while the electron and the muon
asymmetries have to be efficiently washed out by the lightest RH neutrino inverse
processes. Intriguingly, such seemingly special conditions for successful strong ther-
mal leptogenesis are naturally fulfilled within SO(10)-inspired models. Besides the
tauon N2 -dominated scenario, successful strong thermal leptogenesis is also achieved
in scenarios with quasi-degenerate RH neutrino masses. We also comment on the
supersymmetric case. We also derive an expression for the final asymmetry pro-
duced from leptogenesis taking fully into account heavy neutrino flavour effects in
the specific case M1 >> 10^12 GeV (heavy flavoured scenario), a result that can be
extended to any other mass pattern.
Author
Dr
enrico bertuzzo
(Scuola Normale Superiore)
