Probing leptogenesis

Abstract

The focus of this chapter lies on the possible experimental tests of leptogenesis scenarios. We consider both leptogenesis generated from oscillations, as well as leptogenesis from out-of-equilibrium decays. As the Akhmedov-Rubakov-Smirnov (ARS) mechanism allows for heavy neutrinos in the GeV range, this opens up a plethora of possible experimental tests, e.g. at neutrino oscillation experiments, neutrinoless double beta decay, and direct searches for neutral heavy leptons at future facilities. In contrast, testing leptogenesis from out-ofequilibrium decays is a quite difficult task. We comment on the necessary conditions for having successful leptogenesis at the TeV-scale. We further discuss possible realizations and their model specific testability in extended seesaw models, models with extended gauge sectors, and supersymmetric leptogenesis. Not being able to test high-scale leptogenesis directly, we present a way to falsify such scenarios by focusing on their washout processes. This is discussed specifically for the left-right symmetric model and the observation of a heavy WR, as well as model independently when measuring ∆L = 2 washout processes at the LHC or neutrinoless double beta decay. 3

Type I seesaw mechanism as the common origin of neutrino mass, baryon asymmetry, and the electroweak scale

“…3 and 4 display the symmetry and reflection properties that we anticipated in Eq. (16). Our results are thus invariant under the different operations on the RHN Yukawa couplings shown in Eq.…”

“…Our results are thus invariant under the different operations on the RHN Yukawa couplings shown in Eq. (16). In particular, we observe that the dependence of δM max on z R is mostly controlled by the sin (2z R ) term in Eq.…”

“…For a recent series of review papers on leptogenesis, see Refs. [12][13][14][15][16]. However, also the Majorana-neutrino scenario comes with a number of challenges and drawbacks.…”

NA62 sensitivity to heavy neutral leptons in the low scale seesaw model

“…Such peak searches have been performed and are known to reach deep into the region [33] where leptogenesis is feasible in the νMSM [15,34,35]. An interesting point in this context is the extremely good mass resolution, of order of few MeV, which would allow to test the leptogenesis hypothesis [36] in part of the parameter space [37][38][39] if any HNLs are discovered. The…”

Exploring CP-violating heavy neutrino oscillations in rare tau decays at Belle II

“…Recently, NOs experiments have shown that the mixing-angle θ 13 is non zero [35] and also suggest the possibility of CP violation in the light neutrino sector [36]. However, extra sources of CP violation are needed in order to explain the BAU via Leptogenesis (see [37] for a review). In addition, when heavy neutrino masses are below the electroweak scale (M N < 246 GeV), the BAU is generated via CP-violating of Heavy Neutrino Oscillations (HNOs) during their production [38].…”