Dark Matter as the Z_2 Partner of the Standard Model Higgs Boson
Abstract
A possible gamma-ray excess from the Galactic halo favors dark matter with a mass of several hundred GeV. In previous work, we found that an electroweak scalar doublet is a particularly economical, and nearly uniquely selected, interpretation among simple renormalizable thermal dark-matter models. We point out that its unbroken Z_2 symmetry is exactly equivalent to an interchange symmetry between two Higgs doublets, making dark matter the Z_2-odd partner of the Standard Model Higgs boson and suggesting that the two doublets may share a common weak-scale origin. We connect this model to the recently reported 248 keV nuclear-recoil event in the LUX-ZEPLIN experiment. For dark-matter masses of 440--600 GeV, a technically natural, mass-dependent neutral-state splitting of order 350 keV defines a narrow strip near the kinematic boundary where the fixed off-diagonal Z interaction can produce the observed recoil. Because the scattering probes the extreme high-velocity tail of the Galactic distribution, this interpretation predicts a large annual modulation, with future events preferentially occurring around early summer. Neither observation is yet conclusive, but their common interpretation is sharply testable.
Related
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BibTeX
@misc{nomura2026dark,
title = {{Dark Matter as the Z_2 Partner of the Standard Model Higgs Boson}},
author = {Yasunori Nomura},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.02505},
eprint = {2609.02505},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.02505},
}
RIS
TY - UNPB
TI - Dark Matter as the Z_2 Partner of the Standard Model Higgs Boson
AU - Yasunori Nomura
PY - 2026
DA - 2026/09/05
PB - arXiv
DO - 10.48550/arxiv.2609.02505
UR - https://arxiv.org/abs/2609.02505
AB - A possible gamma-ray excess from the Galactic halo favors dark matter with a mass of several hundred GeV. In previous work, we found that an electroweak scalar doublet is a particularly economical, and nearly uniquely selected, interpretation among simple renormalizable thermal dark-matter models. We point out that its unbroken Z_2 symmetry is exactly equivalent to an interchange symmetry between two Higgs doublets, making dark matter the Z_2-odd partner of the Standard Model Higgs boson and suggesting that the two doublets may share a common weak-scale origin. We connect this model to the recently reported 248 keV nuclear-recoil event in the LUX-ZEPLIN experiment. For dark-matter masses of 440--600 GeV, a technically natural, mass-dependent neutral-state splitting of order 350 keV defines a narrow strip near the kinematic boundary where the fixed off-diagonal Z interaction can produce the observed recoil. Because the scattering probes the extreme high-velocity tail of the Galactic distribution, this interpretation predicts a large annual modulation, with future events preferentially occurring around early summer. Neither observation is yet conclusive, but their common interpretation is sharply testable.
ER -