Baryon asymmetry of the Universe in the νMSM

Abstract

We perform a detailed analysis of baryon asymmetry generation in the νMSM (an extension of the Standard Model by three singlet Majorana fermions with masses below the Fermi scale). Fixing a number of parameters of the νMSM by the neutrino oscillation data, we determine the remaining domain of the parameter space from the requirement of successful baryogenesis. We derive, in particular, the constraints on the mass splitting of a pair of singlet fermions, and on the strength of their coupling to ordinary leptons, essential for searches of these particles in rare decays of mesons and in beam-dump experiments with intensive proton beams.

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

“…The resulting decay K + → + a N i can be detected with a search for a peak in the missing mass distribution [32], even if the N i itself is not seen. 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 scenarios A)-D) may be compared to the choices 1)-5) listed in table 3b and used in the estimates for the SHiP experiment [94,95] in reference [50], which were introduced in references [31,34]. Scenarios 1)-3) maximise U 2 e , U 2 µ and U 2 τ for NO in view of the constrains from neutrino oscillation experiments at the time when they were proposed.…”

“…neutrino oscillation data (in particular the measurement of θ 13 , which was unknown at the time when the articles in references [31,34] were written).…”

Perspectives for tests of neutrino mass generation at the GeV scale: Experimental reach versus theoretical predictions

“…The SHiP Collaboration obtained their sensitivity to the total activesterile mixing for five different scenarios with these assumptions [115]: where NO (IO) means normal (inverted) ordering of the light neutrinos. The first three scenarios imply that the sterile neutrinos predominantly mix with one flavor (electron, muon, or tau) [100], whereas the last two scenarios are interesting to generate a sufficient amount of baryon asymmetry [120]. Case 2 is SHiP's benchmark scenario, which means that the sensitivity to the total active-sterile mixing is calculated for this case only, whereas the sensitivity for the other cases has been obtained by extrapolating the sensitivity from case 2 by using the ratio among the individual mixing elements.…”

SHiP: a new facility with a dedicated detector to search for new long-lived neutral particles and studying tau neutrino properties

“…[7] with normal hierarchy and a dominant muon coupling, U 2 e : U 2 µ : U 2 τ = 1 : 16 : 3.8, while the right plot refers to the model in Ref. [8] for inverted hierarchy and a dominant electron coupling, U 2 e : U 2 µ : U 2 τ = 46 : 1 : 1. The parameter space explored by SHiP extends in the cosmologically relevant region that is experimentally unexplored.…”