Model-Independent Sideband Constraints on Inelastic Dark Matter at the LZ High-Recoil Candidate
Abstract
The LUX-ZEPLIN experiment has reported one nuclear-recoil event at 248±23stat±23sys keV in a 2.84 tonne−year exposure, with a local significance of 3.4σ. Inelastic (endothermic) dark matter is a natural candidate: its kinematic threshold suppresses low-energy recoils and shifts the signal toward higher recoil energies. We perform a model-independent analysis of the LZ data using two sidebands, without specifying an ultraviolet completion, so our results apply broadly to inelastic dark matter with coherent spin-independent nuclear scattering. For each (mχ,δ) we compute Nlow/Nsig and Nhi/Nsig---predicted count ratios in the sidebands [14,225) keV and (271,800] keV relative to the signal region [225,271] keV. The two ratios vary in opposite directions with δ and are simultaneously optimized at a unique splitting δ⋆. For mχ=1 TeV, δ⋆=339 keV with a combined Poisson tension of ≈1.9σ; over 500 GeV--3 TeV, the tension at δ⋆ rises from ≲1.3σ to ≈2.5σ. Additional suppression arises from the Helm form factor: |FXeHelm|2≃3×10−4 at 248 keV, near its second diffraction zero. A dedicated LZ search over 271<ER<800 keV would provide a decisive test of inelastic dark matter with δ≳330 keV.
Related
- Exothermic and Endothermic Inelastic Dark Matter Interpretations at LZ: Sideband Constraints and Future Prospects
- Direct detection constraints on EFT operators for inelastic dark matter
- Search for Magnetic and Spin-Independent Inelastic Dark Matter with XENONnT
- Solar Neutrino Constraints on Inelastic Dark Matter Scattering in Light of Recent LUX-ZEPLIN Observations
- ALP-mediated inelastic dark matter and the LUX-ZEPLIN high-recoil candidate event LZ230616
BibTeX
@misc{delepine2026modelindependent,
title = {{Model-Independent Sideband Constraints on Inelastic Dark Matter at the LZ High-Recoil Candidate}},
author = {David Delepine and Shaaban Khalil},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.26698},
eprint = {2609.26698},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.26698},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Model-Independent Sideband Constraints on Inelastic Dark Matter at the LZ High-Recoil Candidate
AU - David Delepine
AU - Shaaban Khalil
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.26698
UR - https://arxiv.org/abs/2609.26698
AB - The LUX-ZEPLIN experiment has reported one nuclear-recoil event at 248±23_stat±23_sys keV in a 2.84 tonne−year exposure, with a local significance of 3.4σ. Inelastic (endothermic) dark matter is a natural candidate: its kinematic threshold suppresses low-energy recoils and shifts the signal toward higher recoil energies. We perform a model-independent analysis of the LZ data using two sidebands, without specifying an ultraviolet completion, so our results apply broadly to inelastic dark matter with coherent spin-independent nuclear scattering. For each (m_χ,δ) we compute N_low/N_sig and N_hi/N_sig---predicted count ratios in the sidebands [14,225) keV and (271,800] keV relative to the signal region [225,271] keV. The two ratios vary in opposite directions with δ and are simultaneously optimized at a unique splitting δ^⋆. For m_χ=1 TeV, δ^⋆=339 keV with a combined Poisson tension of ≈1.9σ; over 500 GeV--3 TeV, the tension at δ^⋆ rises from ≲1.3σ to ≈2.5σ. Additional suppression arises from the Helm form factor: |F_Xe^Helm|^2≃3×10^−4 at 248 keV, near its second diffraction zero. A dedicated LZ search over 271<E_R<800 keV would provide a decisive test of inelastic dark matter with δ≳330 keV.
ER -