Sub-MeV gamma-ray lines from an endothermic interpretation of the LZ recoil candidate
Abstract
Endothermic upscattering of heavy dark matter offers a compelling interpretation of the high-energy nuclear-recoil candidate recently reported by LUX-ZEPLIN (LZ), with a characteristic recoil energy ER ∝ δ, where δ is the mass splitting between the dark matter states. Cosmological and experimental constraints motivate the depletion of the primordial heavier state, which can be regenerated in the Galactic halo. We show that, if the heavier state decays radiatively, the same mass splitting sets the energy of a gamma-ray line, Eγ≃ δ. For our benchmark, this leads to a sub-MeV line within the projected reach of the Compton Spectrometer and Imager (COSI), scheduled for launch in 2027. The confirmation of the LZ candidate event as a dark matter signal would therefore motivate dedicated searches for sub-MeV gamma-ray lines, with COSI providing a timely opportunity to test this interpretation.
Related
- 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
- Exothermic Higgs portal: from LUX-ZEPLIN recoil to Gamma Rays
- A Comprehensive Interpretation of the LZ High-Energy Recoil Event: A Minimal U(1)B Dark Sector and Its Experimental Tests
BibTeX
@misc{dutra2026submev,
title = {{Sub-MeV gamma-ray lines from an endothermic interpretation of the LZ recoil candidate}},
author = {Maíra Dutra and Jacinto P. Neto and Clarissa Siqueira},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.33952},
eprint = {2609.33952},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.33952},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Sub-MeV gamma-ray lines from an endothermic interpretation of the LZ recoil candidate
AU - Maíra Dutra
AU - Jacinto P. Neto
AU - Clarissa Siqueira
PY - 2026
DA - 2026/09/27
PB - arXiv
DO - 10.48550/arxiv.2609.33952
UR - https://arxiv.org/abs/2609.33952
AB - Endothermic upscattering of heavy dark matter offers a compelling interpretation of the high-energy nuclear-recoil candidate recently reported by LUX-ZEPLIN (LZ), with a characteristic recoil energy E_R ∝ δ, where δ is the mass splitting between the dark matter states. Cosmological and experimental constraints motivate the depletion of the primordial heavier state, which can be regenerated in the Galactic halo. We show that, if the heavier state decays radiatively, the same mass splitting sets the energy of a gamma-ray line, E_γ≃ δ. For our benchmark, this leads to a sub-MeV line within the projected reach of the Compton Spectrometer and Imager (COSI), scheduled for launch in 2027. The confirmation of the LZ candidate event as a dark matter signal would therefore motivate dedicated searches for sub-MeV gamma-ray lines, with COSI providing a timely opportunity to test this interpretation.
ER -