Endothermic dark matter with a light dark photon and the LUX-ZEPLIN high-energy nuclear-recoil candidate
- 1CSSM and ARC Centre of Excellence for Dark Matter Particle Physics , Department of Physics , Adelaide University , Adelaide 5005 , Australia
Abstract
The LUX-ZEPLIN (LZ) experiment has reported an inelastic nuclear-recoil candidate at Enr=248±23stat±23sys keV. We test whether endothermic pseudo-Dirac dark matter coupled to a kinetically mixed dark photon can account for this event while reproducing the observed relic abundance. A five-parameter fit using an energy-only LZ likelihood and a relic-density likelihood favors TeV-scale dark matter with a mass splitting of a few hundred keV, and a GeV-scale mediator. The recoil energy places the splitting near its kinematic ceiling, while secluded annihilation fixes the dark gauge coupling to a good approximation as a function of the dark-matter mass. Representative points predict 𝒪(1) accepted LZ event candidate and the observed DM relic density. Because the preferred splitting lies below the e+e- threshold, the viability of the minimal model depends on the late-time excited-state abundance; a transition dipole can provide additional depletion, and the required light mediator remains testable in accelerator searches.
Related
- Galactic Endothermic Production and Exothermic Detection of Excited Dark Matter: Implications for LUX-ZEPLIN
- A Vector-Like Lepton Interpretation of the High-Energy Nuclear Recoil Candidate in LUX-ZEPLIN
- Higgsino Dark Matter Interpretation of the LUX-ZEPLIN 248 keV Nuclear-Recoil Event
- Inelastic Dark Photon Dark Matter for the LUX-ZEPLIN High-Recoil Event and the Galactic Halo Gamma-Ray Excess
- Sub-TeV Singlino Dark Matter in light from Sagittarius A∗ and LUX-ZEPLIN Nuclear-Recoil Event
BibTeX
@misc{zhu2026endothermic,
title = {{Endothermic dark matter with a light dark photon and the LUX-ZEPLIN high-energy nuclear-recoil candidate}},
author = {Pengxuan Zhu and Giovani Dalla Valle Garcia and X. G. Wang and Anthony W. Thomas and Martin J. White},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09015},
eprint = {2609.09015},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09015},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Endothermic dark matter with a light dark photon and the LUX-ZEPLIN high-energy nuclear-recoil candidate
AU - Pengxuan Zhu
AU - Giovani Dalla Valle Garcia
AU - X. G. Wang
AU - Anthony W. Thomas
AU - Martin J. White
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.09015
UR - https://arxiv.org/abs/2609.09015
AB - The LUX-ZEPLIN (LZ) experiment has reported an inelastic nuclear-recoil candidate at E_nr=248±23_stat±23_sys keV. We test whether endothermic pseudo-Dirac dark matter coupled to a kinetically mixed dark photon can account for this event while reproducing the observed relic abundance. A five-parameter fit using an energy-only LZ likelihood and a relic-density likelihood favors TeV-scale dark matter with a mass splitting of a few hundred keV, and a GeV-scale mediator. The recoil energy places the splitting near its kinematic ceiling, while secluded annihilation fixes the dark gauge coupling to a good approximation as a function of the dark-matter mass. Representative points predict 𝒪(1) accepted LZ event candidate and the observed DM relic density. Because the preferred splitting lies below the e^+e^- threshold, the viability of the minimal model depends on the late-time excited-state abundance; a transition dipole can provide additional depletion, and the required light mediator remains testable in accelerator searches.
SN - 2331-8422
ER -