Mixing-suppressed inelastic dark matter: a minimal model for the LZ 248 keV event
- 1Quantum Universe Center , KIAS , 85 Hoegi-ro , Dongdaemun-gu , Seoul 02455 , Korea
- 2School of Physics , KIAS , 85 Hoegi-ro , Dongdaemun-gu , Seoul 02455 , Korea
- 3Gravity, Spacetime, and Particle Physics (GRASP) Initiative , Harvard University , 17 Oxford Street , Cambridge , MA 02138 , USA
Abstract
We construct a minimal Majorana singlet-vector-like-doublet model for the single nuclear-recoil-like event reported by LZ near 248 keV. At the splitting inferred from the recoil energy, an electroweak-strength Z transition predicts thousands of events; singlet-doublet mixing suppresses the rate without moving the recoil spectrum. Fixed-coupling interpretations instead require a larger splitting in the extreme halo tail, but solar gravitational acceleration removes this suppression, while the larger splitting shifts recoils toward LZ's empty high-energy sideband. In our model the same mixing suppresses solar capture and annihilation, while the small mass gap required for coannihilation weakens Higgs-mediated cooling, allowing the captured population to remain extended and out of equilibrium. Imposing the relic abundance and normalizing the rate to one event leaves a two-dimensional mass-splitting parameter space. A thermalized population gives the conservative IceCube limit δ=300-301 keV; with our nonthermal cooling ansatz and elastic scattering treated at tree level, the nominal limit is δ=331-341 keV near the 730-733 GeV relic-density endpoint, which is also favored by the recoil spectrum. We outline a gauged U(1)N origin for the parity and splitting and a candidate R-symmetric supersymmetric embedding.
Related
- Solar Capture and Suppressed Annihilation of Inelastic Scalar Dark Matter
- Explaining the LZ High-Energy Recoil Event with Inelastic Sneutrino Dark Matter in Supersymmetry
- Inelastic Dark Matter from a Higher-Dimensional Operator: The LUX-ZEPLIN High-Recoil Event and Thermal Relic
- Inelastic B−L scalar dark matter and the LUX-ZEPLIN event
- Generalized Chiral U(1)B−L with Inelastic Scalar Dark Matter for the LZ 248 keV Event
BibTeX
@misc{lee2026mixingsuppressed,
title = {{Mixing-suppressed inelastic dark matter: a minimal model for the LZ 248 keV event}},
author = {Seung J. Lee and Taewook Youn},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09138},
eprint = {2609.09138},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09138},
}
RIS
TY - UNPB
TI - Mixing-suppressed inelastic dark matter: a minimal model for the LZ 248 keV event
AU - Seung J. Lee
AU - Taewook Youn
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.09138
UR - https://arxiv.org/abs/2609.09138
AB - We construct a minimal Majorana singlet-vector-like-doublet model for the single nuclear-recoil-like event reported by LZ near 248 keV. At the splitting inferred from the recoil energy, an electroweak-strength Z transition predicts thousands of events; singlet-doublet mixing suppresses the rate without moving the recoil spectrum. Fixed-coupling interpretations instead require a larger splitting in the extreme halo tail, but solar gravitational acceleration removes this suppression, while the larger splitting shifts recoils toward LZ's empty high-energy sideband. In our model the same mixing suppresses solar capture and annihilation, while the small mass gap required for coannihilation weakens Higgs-mediated cooling, allowing the captured population to remain extended and out of equilibrium. Imposing the relic abundance and normalizing the rate to one event leaves a two-dimensional mass-splitting parameter space. A thermalized population gives the conservative IceCube limit δ=300-301 keV; with our nonthermal cooling ansatz and elastic scattering treated at tree level, the nominal limit is δ=331-341 keV near the 730-733 GeV relic-density endpoint, which is also favored by the recoil spectrum. We outline a gauged U(1)_N origin for the parity and splitting and a candidate R-symmetric supersymmetric embedding.
SN - 2331-8422
ER -