The LZ event with a two-state dark matter halo
Abstract
The LUX-ZEPLIN (LZ) experiment has reported a single nuclear-recoil candidate at ER ≃ 248keV. LZ interprets it in terms of inelastic dark matter that scatters endothermically from its ground state, χ1 N → χ2 N. In pseudo-Dirac models the excited state χ2 can survive to the present day, and exothermic scattering, χ2 N → χ1 N, is then also open. The published LZ intervals do not describe this case. We rebuild the LZ statistical inference and validate it against the published intervals. We then apply it to a halo that contains a fraction f of χ2. For f ≳ 10−5--10−2, depending on the mass splitting, the exothermic contribution dominates. For f=1/2 the cross section required by the candidate drops by factors of $80$ to 1.6×104 for δ= 250--$350$~keV, and the kinematic cutoff of the endothermic signal disappears. A benchmark that explains the event with χ1 alone lies a factor of $30$ above the upper limit when half of the halo is χ2.
Related
- Inelastic Dark Photon Dark Matter for the LUX-ZEPLIN High-Recoil Event and the Galactic Halo Gamma-Ray Excess
- The high-velocity dark matter halo of the Milky Way in light of the LZ 248 keV event
- Temporal Correlations Between Fuzzy Dark Matter and Baryonic Matter in Virialized Core-Halo Structures
- A Graph Attention Network Framework for Simultaneous Prediction of Galaxy and Dark Matter Halo Properties in GAMA DR4
- The Contribution of Mergers and Accretion to Dark Matter Halo Assembly: An Excursion Set Theory Approach
BibTeX
@misc{oliveira2026event,
title = {{The LZ event with a two-state dark matter halo}},
author = {Vinicius Oliveira},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.35650},
eprint = {2609.35650},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.35650},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The LZ event with a two-state dark matter halo
AU - Vinicius Oliveira
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.35650
UR - https://arxiv.org/abs/2609.35650
AB - The LUX-ZEPLIN (LZ) experiment has reported a single nuclear-recoil candidate at E_R ≃ 248keV. LZ interprets it in terms of inelastic dark matter that scatters endothermically from its ground state, χ_1 N → χ_2 N. In pseudo-Dirac models the excited state χ_2 can survive to the present day, and exothermic scattering, χ_2 N → χ_1 N, is then also open. The published LZ intervals do not describe this case. We rebuild the LZ statistical inference and validate it against the published intervals. We then apply it to a halo that contains a fraction f of χ_2. For f ≳ 10^−5--10^−2, depending on the mass splitting, the exothermic contribution dominates. For f=1/2 the cross section required by the candidate drops by factors of $80$ to 1.6×10^4 for δ= 250--$350$~keV, and the kinematic cutoff of the endothermic signal disappears. A benchmark that explains the event with χ_1 alone lies a factor of $30$ above the upper limit when half of the halo is χ_2.
ER -