Hybrid seesaw leptogenesis and TeV singlets

Abstract

The appealing feature of inverse seesaw models is that the Standard Model (SM) neutrino mass emerges from the exchange of TeV scale singlets with sizable Yukawa couplings, which can be tested at colliders. However, the tiny Majorana mass splitting between TeV singlets, introduced to accommodate small neutrino masses, is left unexplained. Moreover, we argue that these models suffer from a structural limitation that prevents a successful leptogenesis if one insists on having unsuppressed Yukawa couplings and TeV scale singlets. In this work we propose a hybrid seesaw model, where we replace the mass splitting with a coupling to a high scale seesaw module including a TeV scalar. We show that this structure achieves the goal of filling both the above gaps with couplings of order unity. The necessary structure automatically arises embedding the seesaw mechanism in composite Higgs models, but may also be enforced by new gauge symmetries in a weakly-coupled theory. Our hybrid seesaw models have distinguishing features compared to the standard high scale type-I seesaw and inverse seesaw. Firstly, they have much richer phenomenology. Indeed, they generally predict new TeV scale physics (including scalars) potentially accessible at present and future colliders, whereas weakly-coupled versions may also have astrophysical and cosmological signatures due to the presence of a light Nambu-Goldstone boson coupled to neutrinos. Secondly, our scenario features an interesting interplay between high scale and TeV scale physics in leptogenesis and enlarges the range of allowed high scale singlet masses beyond the usual $\sim 10^9-10^{15}$ GeV, without large hierarchies in the Yukawa couplings nor small mass splitting among the singlets.

21 pages, 1 figure

References in corpus (11)

• Leptogenesis
• A Joint Analysis of BICEP2/Keck Array and Planck Data
• Big-Bang Nucleosynthesis and Gravitino
• The Minimal Set of Electroweak Precision Parameters
• Flavour Covariant Transport Equations: an Application to Resonant Leptogenesis
• Lepton Flavour Violation and theta(13) in Minimal Resonant Leptogenesis
• Leptogenesis with TeV Scale Inverse Seesaw in SO(10)
• Neutrino masses, leptogenesis and dark matter from small lepton number violation?
• Minimal Dynamical Inverse See Saw
• Neutrino mass and invisible Higgs decays at the LHC
• Lepton Number Violation: Seesaw Models and Their Collider Tests

Cited by in corpus (11)

• Assessing Perturbativity and Vacuum Stability in High-Scale Leptogenesis
• Natural Seesaw and Leptogenesis from Hybrid of High-Scale Type I and TeV-Scale Inverse
• Low Scale Left-Right Symmetry and Naturally Small Neutrino Mass
• Undemocratic Dirac seesaw
• Common origin of inverse seesaw and baryon asymmetry
• Low-scale Leptogenesis with Minimal Lepton Flavour Violation
• Minimal inverse seesaw accompanied by Dirac fermionic dark matter
• Conformal Leptogenesis in Composite Higgs Models
• Matter and dark matter asymmetry from a composite Higgs model
• Light Sterile Neutrino and Low Scale Left-Right Symmetry in D-brane inspired $SU(4{)}_C\times SU(2{)}_L\times SU(2{)}_R$
• Leptogenesis assisted by scalar decays