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| Natura: | Preprint |
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2026
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| Accesso online: | https://arxiv.org/abs/2605.09979 |
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| _version_ | 1866916000068272128 |
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| author | Yamashita, Kimiko |
| author_facet | Yamashita, Kimiko |
| contents | 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 scalar mediator with a mass of around 400 MeV, which couples to the dark photon mass operator in order to enhance the present-day annihilation rate in the Galactic halo without affecting the freeze-out dynamics. 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_09979 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Higgs-Portal Spin-1 Dark Matter with Parity-Violating Interaction for a Galactic Halo Gamma Ray Excess Yamashita, Kimiko High Energy Physics - Phenomenology 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 scalar mediator with a mass of around 400 MeV, which couples to the dark photon mass operator in order to enhance the present-day annihilation rate in the Galactic halo without affecting the freeze-out dynamics. 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. |
| title | Higgs-Portal Spin-1 Dark Matter with Parity-Violating Interaction for a Galactic Halo Gamma Ray Excess |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2605.09979 |