Dark Matter as the Z2 Partner of the Standard Model Higgs Boson
4 affiliations
- 1Kavli Institute for the Physics and Mathematics of the Universe (WPI), UTIAS, The University of Tokyo, Kashiwa 277-8583, Japan
- 2Leinweber Institute for Theoretical Physics, Department of Physics, University of California, Berkeley, CA 94720, USA
- 3RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), RIKEN, Wako 351-0198, Japan
- 4Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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 Z2 symmetry is exactly equivalent to an interchange symmetry between two Higgs doublets, making dark matter the Z2-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 248keV nuclear-recoil event in the LUX-ZEPLIN experiment. For dark-matter masses of several hundred GeV, the fixed off-diagonal Z interaction can produce the observed recoil within a narrow, halo-dependent strip near the kinematic boundary, predicting a large annual modulation for a smooth Standard Halo Model. Dedicated solar-capture calculations, however, exclude this Standard-Halo interpretation in the thermal-relic mass range. An enhanced high-velocity tail, potentially associated with the Large Magellanic Cloud, shifts the LZ-preferred splitting upward and may leave marginal compatibility with the solar-neutrino constraint. The solar-neutrino constraint does not affect the identification of inert-doublet dark matter as the Z2 partner of the Standard Model Higgs boson or its possible connection to the Galactic halo excess.
Related
- Dark photon and U(1)B−L gauge boson from dark Higgs boson decays at FASER and SHiP
- Probing pair production of long-lived scalars via an off-shell Standard-Model-like Higgs boson at the LHC
- Dark photons in exotic Higgs boson decays at FCC-ee
- Search for dark photons from Higgs boson decays in the gluon-gluon fusion channel in proton-proton collisions at √s=13.6 TeV with the ATLAS detector
- Exothermic Dark Matter with a Dark Higgs: The LZ 248 keV Event and the Galactic Center Excess
BibTeX
@article{nomura2026dark,
title = {{Dark Matter as the Z2 Partner of the Standard Model Higgs Boson}},
author = {Yasunori Nomura},
journal = {Symmetry},
year = {2026},
month = oct,
doi = {10.3390/sym18111777},
url = {https://doi.org/10.3390/sym18111777},
note = {CC BY},
}
RIS
TY - JOUR
TI - Dark Matter as the Z2 Partner of the Standard Model Higgs Boson
AU - Yasunori Nomura
PY - 2026
DA - 2026/10/25
JO - Symmetry
DO - 10.3390/sym18111777
UR - https://doi.org/10.3390/sym18111777
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 Z2 symmetry is exactly equivalent to an interchange symmetry between two Higgs doublets, making dark matter the Z2-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 248keV nuclear-recoil event in the LUX-ZEPLIN experiment. For dark-matter masses of several hundred GeV, the fixed off-diagonal Z interaction can produce the observed recoil within a narrow, halo-dependent strip near the kinematic boundary, predicting a large annual modulation for a smooth Standard Halo Model. Dedicated solar-capture calculations, however, exclude this Standard-Halo interpretation in the thermal-relic mass range. An enhanced high-velocity tail, potentially associated with the Large Magellanic Cloud, shifts the LZ-preferred splitting upward and may leave marginal compatibility with the solar-neutrino constraint. The solar-neutrino constraint does not affect the identification of inert-doublet dark matter as the Z2 partner of the Standard Model Higgs boson or its possible connection to the Galactic halo excess.
SN - 2073-8994
ER -