Inelastic Dark Matter at LZ from Radiative Dirac Neutrino Mass Paradigm
Abstract
The LUX-ZEPLIN (LZ) experiment has reported a high-energy nuclear recoil candidate, LZ230616, at ER = 248 ± 23stat ± 23syskeV, which is difficult to reconcile with elastic scattering of halo dark matter (DM). Endothermic inelastic scattering offers a natural explanation, but it rests on a nucleon coupling that is off-diagonal rather than diagonal. We show that this feature arises automatically within a radiative Dirac neutrino mass framework. The Standard Model is extended by three right-handed neutrinos (RHNs), a pair of vector-like neutral fermions for each generations, and a scalar sector comprising an inert doublet and a real singlet, governed by a 𝒵2 × 𝒵4 symmetry. The 𝒵2 symmetry stabilizes the DM, while the 𝒵4 symmetry forbids the tree-level Dirac Yukawa coupling together with all renormalizable Majorana mass terms, thereby allowing the generation of Dirac neutrino masses at the one-loop level through a softly broken scalar trilinear coupling `κ'. Since the neutral dark-sector fields can be expressed in terms of real scalar mass eigenstates, the Z boson couples to them purely off-diagonally and elastic Z-mediated scattering is absent identically rather than simply suppressed. The singlet--doublet mixing induced by `κ' governs both the inelastic rate and the one-loop Dirac neutrino mass, which therefore vanish as κ→ 0. We find that DM masses in the few hundred GeV to TeV range, with splittings of 𝒪(340−360) keV, simultaneously reproduce the observed relic abundance, account for the LZ event and yield neutrino masses of the correct order, while respecting elastic direct-detection limits and all relevant theoretical and experimental constraints. A substantial part of the surviving parameter space lies within reach of DARWIN.
Related
- Solar Neutrino Constraints on Inelastic Dark Matter Scattering in Light of Recent LUX-ZEPLIN Observations
- Inelastic Self-interacting Dark Matter and LUX-ZEPLIN 248 keV Event in a Dirac Modular Inverse Seesaw
- Singlet-doublet dark matter induced radiative neutrino mass and TeV scale leptogenesis
- Direct detection constraints on EFT operators for inelastic dark matter
- Leptogenesis with a GeV-Scale Quasi-Dirac Neutrino
BibTeX
@misc{borah2026inelastic,
title = {{Inelastic Dark Matter at LZ from Radiative Dirac Neutrino Mass Paradigm}},
author = {Pankaj Borah and Satyabrata Mahapatra and Newton Nath},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.15027},
eprint = {2609.15027},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.15027},
}
RIS
TY - UNPB
TI - Inelastic Dark Matter at LZ from Radiative Dirac Neutrino Mass Paradigm
AU - Pankaj Borah
AU - Satyabrata Mahapatra
AU - Newton Nath
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.15027
UR - https://arxiv.org/abs/2609.15027
AB - The LUX-ZEPLIN (LZ) experiment has reported a high-energy nuclear recoil candidate, LZ230616, at E_R = 248 ± 23_stat ± 23_syskeV, which is difficult to reconcile with elastic scattering of halo dark matter (DM). Endothermic inelastic scattering offers a natural explanation, but it rests on a nucleon coupling that is off-diagonal rather than diagonal. We show that this feature arises automatically within a radiative Dirac neutrino mass framework. The Standard Model is extended by three right-handed neutrinos (RHNs), a pair of vector-like neutral fermions for each generations, and a scalar sector comprising an inert doublet and a real singlet, governed by a 𝒵_2 × 𝒵_4 symmetry. The 𝒵_2 symmetry stabilizes the DM, while the 𝒵_4 symmetry forbids the tree-level Dirac Yukawa coupling together with all renormalizable Majorana mass terms, thereby allowing the generation of Dirac neutrino masses at the one-loop level through a softly broken scalar trilinear coupling `κ'. Since the neutral dark-sector fields can be expressed in terms of real scalar mass eigenstates, the Z boson couples to them purely off-diagonally and elastic Z-mediated scattering is absent identically rather than simply suppressed. The singlet--doublet mixing induced by `κ' governs both the inelastic rate and the one-loop Dirac neutrino mass, which therefore vanish as κ→ 0. We find that DM masses in the few hundred GeV to TeV range, with splittings of 𝒪(340−360) keV, simultaneously reproduce the observed relic abundance, account for the LZ event and yield neutrino masses of the correct order, while respecting elastic direct-detection limits and all relevant theoretical and experimental constraints. A substantial part of the surviving parameter space lies within reach of DARWIN.
ER -