Higgs-Portal Spin-1 Dark Matter with Parity-Violating Interaction for a Galactic Halo Gamma Ray Excess
Abstract
We study a dark photon dark matter scenario associated with a gauged U(1)X symmetry, stabilized by a dark parity that forbids kinetic mixing with the Standard Model. The leading interactions between the dark photon dark matter and the Standard Model arise from dimension-six Higgs-portal operators. In previous work, we found that for the parity-violating operator, the dark matter annihilation process is p-wave suppressed, naturally evading stringent direct-detection constraints while reproducing the observed relic abundance through thermal freeze-out. For a cutoff scale of 1 TeV, a dark matter mass of around 400 GeV is favored to realize the observed relic abundance. This scenario predicts cosmic-ray signals, in particular in the W+W− channel, which can be targeted by indirect-detection experiments. Recently, a halo-like gamma-ray excess has been reported by Totani. Assuming a Navarro-Frenk-White-ρ2 morphology for the dark matter distribution,a dark matter mass of 420 GeV is favored for the W+W− final state. Motivated by this excess, we consider the present dark photon dark matter framework augmented by a CP-even sub-GeV scalar mediator, which couples to the dark photon mass operator in order to enhance the present-day annihilation rate in the Galactic halo while inducing only an O(1) correction at freeze-out. The exchange of this scalar induces a long-range attractive force, leading to Sommerfeld enhancement of the annihilation rate. The enhancement is saturating in dwarf spheroidal galaxies and the annihilation rate is dropping as p-wave remaining consistent with constraints from dwarf galaxies and cosmology.
Versions
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BibTeX
@misc{yamashita2026higgsportal,
title = {{Higgs-Portal Spin-1 Dark Matter with Parity-Violating Interaction for a Galactic Halo Gamma Ray Excess}},
author = {Kimiko Yamashita},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2605.09979},
eprint = {2605.09979},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.09979},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Higgs-Portal Spin-1 Dark Matter with Parity-Violating Interaction for a Galactic Halo Gamma Ray Excess
AU - Kimiko Yamashita
PY - 2026
DA - 2026/09/26
PB - arXiv
DO - 10.48550/arxiv.2605.09979
UR - https://arxiv.org/abs/2605.09979
AB - We study a dark photon dark matter scenario associated with a gauged U(1)_X symmetry, stabilized by a dark parity that forbids kinetic mixing with the Standard Model. The leading interactions between the dark photon dark matter and the Standard Model arise from dimension-six Higgs-portal operators. In previous work, we found that for the parity-violating operator, the dark matter annihilation process is p-wave suppressed, naturally evading stringent direct-detection constraints while reproducing the observed relic abundance through thermal freeze-out. For a cutoff scale of 1 TeV, a dark matter mass of around 400 GeV is favored to realize the observed relic abundance. This scenario predicts cosmic-ray signals, in particular in the W^+W^− channel, which can be targeted by indirect-detection experiments. Recently, a halo-like gamma-ray excess has been reported by Totani. Assuming a Navarro-Frenk-White-ρ^2 morphology for the dark matter distribution,a dark matter mass of 420 GeV is favored for the W^+W^− final state. Motivated by this excess, we consider the present dark photon dark matter framework augmented by a CP-even sub-GeV scalar mediator, which couples to the dark photon mass operator in order to enhance the present-day annihilation rate in the Galactic halo while inducing only an O(1) correction at freeze-out. The exchange of this scalar induces a long-range attractive force, leading to Sommerfeld enhancement of the annihilation rate. The enhancement is saturating in dwarf spheroidal galaxies and the annihilation rate is dropping as p-wave remaining consistent with constraints from dwarf galaxies and cosmology.
ER -