Endothermic Dark Matter at LZ from a Decaying Parent
Abstract
The LUX-ZEPLIN experiment has reported a nuclear-recoil candidate near 248 keV. We investigate a decay source for an endothermic interpretation: a long-lived dark parent produces energetic ground-state particles that upscatter on xenon. The parent mass fixes the injection energy, while its lifetime determines the absolute flux through the Galactic dark-matter column density. We include the Doppler broadening from parent and observer motion and use exact scattering kinematics with natural xenon isotopes. For a scalar contact interaction, a benchmark with a 10 MeV incident state and a 506 MeV parent gives an efficiency-weighted recoil spectrum peaked at 248.5 keV. One event in a specified high-energy window requires τX ≃ 4.4 × 1020 s fX [σref/(10−36 cm2)], with a normalization sensitive to the nuclear response. We quantify the accompanying elastic-scattering requirement and the target-dependent thresholds. The calculation identifies a decay realization of the boosted flux and the portal conditions needed to preserve the recoil signal; a detector-level fit and ultraviolet-specific constraints remain necessary for a complete experimental assessment.
Related
- Galactic Endothermic Production and Exothermic Detection of Excited Dark Matter: Implications for LUX-ZEPLIN
- Endothermic dark matter with a light dark photon and the LUX-ZEPLIN high-energy nuclear-recoil candidate
- Endothermic Z'-Portal Dark Matter: LZ-LHC Complementarity
- Exothermic and Endothermic Inelastic Dark Matter Interpretations at LZ: Sideband Constraints and Future Prospects
- Constraints on Decaying Dark Matter with B=1 from Fermi-LAT
BibTeX
@misc{jho2026endothermic,
title = {{Endothermic Dark Matter at LZ from a Decaying Parent}},
author = {Yongsoo Jho and Sanghwan Kim and Seong Chan Park},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37545},
eprint = {2609.37545},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37545},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Endothermic Dark Matter at LZ from a Decaying Parent
AU - Yongsoo Jho
AU - Sanghwan Kim
AU - Seong Chan Park
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37545
UR - https://arxiv.org/abs/2609.37545
AB - The LUX-ZEPLIN experiment has reported a nuclear-recoil candidate near 248 keV. We investigate a decay source for an endothermic interpretation: a long-lived dark parent produces energetic ground-state particles that upscatter on xenon. The parent mass fixes the injection energy, while its lifetime determines the absolute flux through the Galactic dark-matter column density. We include the Doppler broadening from parent and observer motion and use exact scattering kinematics with natural xenon isotopes. For a scalar contact interaction, a benchmark with a 10 MeV incident state and a 506 MeV parent gives an efficiency-weighted recoil spectrum peaked at 248.5 keV. One event in a specified high-energy window requires τ_X ≃ 4.4 × 10^20 s f_X [σ_ref/(10^−36 cm^2)], with a normalization sensitive to the nuclear response. We quantify the accompanying elastic-scattering requirement and the target-dependent thresholds. The calculation identifies a decay realization of the boosted flux and the portal conditions needed to preserve the recoil signal; a detector-level fit and ultraviolet-specific constraints remain necessary for a complete experimental assessment.
ER -