Abstract
We consider sub-TeV scale flavoured resonant leptogenesis within the minimal type-I seesaw scenario with two right-handed singlet neutrinos N1,2 forming a pseudo-Dirac pair, concentrating on the case of masses of the pseudo-Dirac pair having values M1,2≲100 GeV. The case when the CP violating asymmetries in the individual lepton charges Ll, l=e,μ,τ, and in the total lepton charge L of the Universe are generated in 1↔2 decay processes is investigated. We show that successful leptogenesis is possible for M1,2 lying in the interval M1,2=(0.3−100) GeV. Our results show also, in particular, that for vanishing initial N1,2 abundance, flavour effects can play an important role in the generation of the baryon asymmetry, leading to an enhancement of the asymmetry by a factor up to ∼300 with respect to the “unflavoured” leptogenesis scenario.
Highlights
Understanding the origin of the excess of matter over antimatter - the matter-antimatter or baryon asymmetry - in the Universe remains one of the fundamental problems in particle physics and cosmology
We do not consider in this study the “freeze-in” scenario [35, 36] in which the baryon asymmetry of the Universe (BAU) in leptogenesis is generated via N1 ↔ N2 oscillations during the epoch when N1,2 are out of equilibrium, which has been extensively studied 2
We proceed to show results in two possible scenarios by which the BAU can be produced. They correspond to two different “initial conditions”, i.e., N1,2 initial abundances: i) N1,2 thermal initial abundance (TIA), and ii) N1,2 vanishing initial abundance (VIA)
Summary
Understanding the origin of the excess of matter over antimatter - the matter-antimatter or baryon asymmetry - in the Universe remains one of the fundamental problems in particle physics and cosmology. In the relatively recent article [50] the authors presented a unified framework of generation of the baryon asymmetry at the sub-TeV scale via the neutrino oscillations (“freeze-in”) and the decay RL mechanisms within the scenario with two Majorana neutrinos N1,2 They have shown that i) the observed baryon asymmetry can be generated for all experimentally allowed values of the Majorana neutrino masses M1,2 100 MeV and up to M1,2 ∼ 1 TeV, and that ii) leptogenesis is effective in a broad range of the relevant parameters, including mass splitting between the two Majorana neutrinos as big as (M2 − M1)/(0.5(M2 + M1)) ∼ 0.1, as well as couplings of N1,2 in the weak charged lepton current large enough to be accessible to planned intensity experiments or future colliders.
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