Abstract
We analyse the feasibility of low-scale leptogenesis where the inverse seesaw (ISS) and linear seesaw (LSS) terms are not simultaneously present. In order to generate the necessary mass splittings, we adopt a Minimal Lepton Flavour Violation (MLFV) hypothesis where a sterile neutrino mass degeneracy is broken by flavour effects. We find that resonant leptogenesis is feasible in both scenarios. However, because of a flavour alignment issue, MLFV-ISS leptogenesis succeeds only with a highly tuned choice of Majorana masses. For MLFV-LSS, on the other hand, a large portion of parameter space is able to generate sufficient asymmetry. In both scenarios we find that the lightest neutrino mass must be of order $10^{-2}\text{ eV}$ or below for successful leptogenesis. We briefly explore implications for low-energy flavour violation experiments, in particular $\mu \rightarrow e\,\gamma$. We find that the future MEG-II experiment, while sensitive to MLFV in our setup, will not be sensitive to the specific regions required for resonant leptogenesis.
Highlights
The type-I seesaw model [1,2,3,4,5] is the simplest known extension of the Standard Model (SM) that simultaneously addresses the origin of neutrino mass and the generation of the cosmological matter-antimatter asymmetry, the latter through thermal leptogenesis [6]
We have studied a well-motivated way in which small mass splittings between heavy sterile neutrinos (SNs) from different families may arise, within both the inverse seesaw (ISS) and linear seesaw (LSS) frameworks, such that leptogenesis is possible despite the strong washout present in the theory
It was found that while a mass splitting naturally exists for the ISS it is not sufficient in order for resonant leptogenesis to occur
Summary
The type-I seesaw model [1,2,3,4,5] is the simplest known extension of the Standard Model (SM) that simultaneously addresses the origin of neutrino mass and the generation of the cosmological matter-antimatter asymmetry, the latter through thermal leptogenesis [6] (for reviews see [7,8,9]). This scenario has been extensively studied and it has long been known that in the standard hierarchical type-I scenario of thermal leptogenesis, generation of the necessary asymmetry places a lower bound [10,11] on the heavy sterile neutrinos (SNs) of order 109 GeV This prevents low-scale realizations of this model in its simplest form. In order to produce large leptonic flavor violation while suppressing neutrino masses in such models, a separation between the scale of lepton-number violation (LNV) and lepton-flavor violation (LFV) should exist which is not present in the type-I seesaw alone [52,57] Neither of these issues are present for MLFV in the ISS and LSS, allowing the possibility of MLFV-induced resonant leptogenesis in these scenarios.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
