HNL mass degeneracy: implications for low-scale seesaws, LNV at colliders and leptogenesis

Abstract

Low-scale seesaw variants protected by lepton number symmetry provide a natural explanation of the smallness of neutrino masses but, unlike their higher-scale counterparts, with potentially testable phenomenology. The approximate lepton number symmetry arranges the heavy neutrinos in pseudo-Dirac pairs, which might be accessible at collider or even beam dump experiments if their mass is low enough and their mixing with the active neutrinos sufficiently large. Despite their pseudo-Dirac nature, their small mass splittings may lead to oscillations that prevent the cancellation of their potential lepton-number-violating signals. Interestingly, these small splittings may also resonantly enhance the production of a lepton number asymmetry for low-scale leptogenesis scenarios or, for extremely degenerate states, lead to an asymmetry large enough to resonantly produce a keV sterile neutrino dark matter candidate with the correct relic abundance via the Shi-Fuller mechanism. In this work we explore the parameter space of the different low-scale seesaw mechanisms and study the size of these splittings, given their important and interesting phenomenological consequences. While all low-scale seesaw variants share the same dimension 5 and 6 operators when integrating out the heavy states, we point out that the mass splitting of the pseudo-Dirac pairs are very different in different realizations such as the inverse or linear seesaw. This different phenomenology could offer a way to discriminate between low-scale seesaw realizations.

arXiv comment27 pages, 6 figures. Matches published version in JHEP

References in corpus (53)

• Sterile Neutrinos as Dark Matter
• The fate of hints: updated global analysis of three-flavor neutrino oscillations
• The $\nu$MSM, Dark Matter and Baryon Asymmetry of the Universe
• Resonant Leptogenesis
• A New Dark Matter Candidate: Non-thermal Sterile Neutrinos
• Baryogenesis via neutrino oscillations
• Right-Handed Neutrinos at LHC and the Mechanism of Neutrino Mass Generation
• Novel Supersymmetric SO(10) Seesaw Mechanism
• Radiatively Induced Neutrino Masses and Large Higgs-Neutrino Couplings in the Standard Model with Majorana Fields
• Low energy effects of neutrino masses
• Dark Matter, Baryogenesis and Neutrino Oscillations from Right Handed Neutrinos
• Minimal Flavour Seesaw Models
• Left-Right Symmetry Breaking in NJL Approach
• The nuMSM, leptonic asymmetries, and properties of singlet fermions
• Do experiments suggest a hierarchy problem?
• Dirac or Inverse Seesaw Neutrino Masses with $B-L$ Gauge Symmetry and $S_3$ Flavour Symmetry
• Neutrinoless double beta decay versus other probes of heavy sterile neutrinos
• Looking for the minimal inverse seesaw realisation
• Testable Baryogenesis in Seesaw Models
• Heavy neutrinos and the $pp\to lljj$ CMS data
• Leptogenesis from first principles in the resonant regime
• EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-Poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension
• Large Neutrino Mixing from Small Quark and Lepton Mixings
• Testing the low scale seesaw and leptogenesis
• Can heavy neutrinos dominate neutrinoless double beta decay?
• Same Sign versus Opposite Sign Dileptons as a Probe of Low Scale Seesaw Mechanisms
• Implications for New Physics from Fine-Tuning Arguments: I. Application to SUSY and Seesaw Cases
• TeV Scale Gauged B-L With Inverse Seesaw Mechanism
• ARS Leptogenesis
• Radiative Linear Seesaw model, Dark Matter and $U(1{)}_{B-L}$
• Lepton number violation as a key to low-scale leptogenesis
• GeV-scale neutrinos: interactions with mesons and DUNE sensitivity
• Quasi-Dirac neutrinos at the LHC
• Low-scale leptogenesis with three heavy neutrinos
• Fermionic Dark Matter in Radiative Inverse Seesaw Model with U(1)_{B-L}
• General parametrization of Majorana neutrino mass models
• Neutrino masses, leptogenesis and dark matter from small lepton number violation?
• Sequential Dominance
• On Lepton Number Violation in Heavy Neutrino Decays at Colliders
• Minimal Dynamical Inverse See Saw
• Sterile neutrino dark matter via coinciding resonances
• Constraining a general U(1)${}^{\prime }$ inverse seesaw model from vacuum stability, dark matter and collider
• Collider Searches for Heavy Neutral Leptons: beyond simplified scenarios
• Parameter space of baryogenesis in the $\nu$MSM
• Dynamical Minimal Flavour Violating Inverse Seesaw
• Sterile neutrino dark matter via GeV-scale leptogenesis?
• Dark Matter and the elusive ${\mathbf{Z}}^{\prime }$ in a dynamical Inverse Seesaw scenario
• Bounds on right-handed neutrino parameters from observable leptogenesis
• Gauged Inverse Seesaw from Dark Matter
• Inverse seesaw and $(g-2)$ anomalies in $B-L$ extended two Higgs doublet model
• Non-universal Z' from SO(10) GUTs with vector-like family and the origin of neutrino masses
• Dynamical inverse seesaw mechanism as a simple benchmark for electroweak breaking and Higgs boson studies
• Low-scale leptogenesis with flavour and CP symmetries

Cited by in corpus (9)

• Heavy Neutral Leptons at Muon Colliders
• $\nu$ Electroweak Baryogenesis: The Scalar Singlet Strikes Back
• Charged lepton-flavor violating processes and suppression of nonunitary mixing effects in low-scale seesaw models
• Resonant Majorana neutrino effects in $\Delta$L=2 four-body hyperon decays
• Large lepton number violation at colliders: predictions from the minimal linear seesaw mechanism
• Linear seesaw leptogenesis before/after electroweak symmetry breaking
• Leptogenesis assisted by scalar decays
• Can SUSY relax LNV constraints coming from loop corrections to light neutrino masses on the low-scale Seesaw?
• Impact of dim-6 $\nu$SMEFT operators on low-scale leptogenesis