Natural seesaw and leptogenesis from hybrid of high-scale type I and TeV-scale inverse

  • Kaustubh Agashe
  • Peizhi DuEmail author
  • Majid Ekhterachian
  • Chee Sheng Fong
  • Sungwoo Hong
  • Luca Vecchi
Open Access
Regular Article - Theoretical Physics


We develop an extension of the basic inverse seesaw model which addresses simultaneously two of its drawbacks, namely, the lack of explanation of the tiny Majorana mass term μ for the TeV-scale singlet fermions and the difficulty in achieving successful leptogenesis. Firstly, we investigate systematically leptogenesis within the inverse (and the related linear) seesaw models and show that a successful scenario requires either small Yukawa couplings, implying loss of experimental signals, and/or quasi-degeneracy among singlets mass of different generations, suggesting extra structure must be invoked. Then we move to the analysis of our new framework, which we refer to as hybrid seesaw. This combines the TeV degrees of freedom of the inverse seesaw with those of a high-scale (MN ≫ TeV) seesaw module in such a way as to retain the main features of both pictures: naturally small neutrino masses, successful leptogenesis, and accessible experimental signatures. We show how the required structure can arise from a more fundamental theory with a gauge symmetry or from warped extra dimensions/composite Higgs. We provide a detailed derivation of all the analytical formulae necessary to analyze leptogenesis in this new framework, and discuss the entire gamut of possibilities our scenario encompasses — including scenarios with singlet masses in the enlarged range MN ∼ 106 − 1016 GeV. This idea of hybrid seesaw was proposed by us in arXiv:1804.06847; here, we substantially elaborate upon and extend earlier results.


Beyond Standard Model Cosmology of Theories beyond the SM CP violation Neutrino Physics 


Open Access

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.


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Copyright information

© The Author(s) 2019

Authors and Affiliations

  • Kaustubh Agashe
    • 1
  • Peizhi Du
    • 1
    Email author
  • Majid Ekhterachian
    • 1
  • Chee Sheng Fong
    • 2
  • Sungwoo Hong
    • 3
  • Luca Vecchi
    • 4
  1. 1.Maryland Center for Fundamental Physics, Department of PhysicsUniversity of MarylandCollege ParkU.S.A.
  2. 2.Centro de Ciências Naturais e HumanasUniversidade Federal do ABCSanto AndréBrazil
  3. 3.Department of Physics, LEPPCornell UniversityIthacaU.S.A.
  4. 4.Theoretical Particle Physics Laboratory, Institute of PhysicsEPFLLausanneSwitzerland

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