The LUX-ZEPLIN Event as Hyperfine Spectroscopy of Composite Dark Matter
Abstract
We propose that the 248 keV nuclear-recoil candidate reported by LUX--ZEPLIN can arise from the endothermic hyperfine excitation of composite dark matter. Rather than requiring two distinct dark-sector particles, the inelasticity of scattering arises from a hyperfine transition between the pseudoscalar and vector states of a single dark hadron. In a PQ-augmented dark QCD framework, the parity-conserving vacuum suppresses dangerous elastic scattering, while axion emission depletes the relic excited-state population. Endothermic excitation near the Galactic kinematic edge then naturally produces a localized high-energy recoil peak. We find that sub-TeV-scale dark matter with a hyperfine splitting of a few hundred keV can yield an order-one event rate in the LZ high-recoil window. This interpretation offers a possible form of dark-matter hyperfine spectroscopy, with complementary tests from dark-photon searches and future recoil-spectrum measurements.
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BibTeX
@misc{sheng2026luxzeplin,
title = {{The LUX-ZEPLIN Event as Hyperfine Spectroscopy of Composite Dark Matter}},
author = {Jie Sheng and Kairui Zhang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.23477},
eprint = {2609.23477},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.23477},
note = {CC0},
}
RIS
TY - UNPB
TI - The LUX-ZEPLIN Event as Hyperfine Spectroscopy of Composite Dark Matter
AU - Jie Sheng
AU - Kairui Zhang
PY - 2026
DA - 2026/09/20
PB - arXiv
DO - 10.48550/arxiv.2609.23477
UR - https://arxiv.org/abs/2609.23477
AB - We propose that the 248 keV nuclear-recoil candidate reported by LUX--ZEPLIN can arise from the endothermic hyperfine excitation of composite dark matter. Rather than requiring two distinct dark-sector particles, the inelasticity of scattering arises from a hyperfine transition between the pseudoscalar and vector states of a single dark hadron. In a PQ-augmented dark QCD framework, the parity-conserving vacuum suppresses dangerous elastic scattering, while axion emission depletes the relic excited-state population. Endothermic excitation near the Galactic kinematic edge then naturally produces a localized high-energy recoil peak. We find that sub-TeV-scale dark matter with a hyperfine splitting of a few hundred keV can yield an order-one event rate in the LZ high-recoil window. This interpretation offers a possible form of dark-matter hyperfine spectroscopy, with complementary tests from dark-photon searches and future recoil-spectrum measurements.
ER -