Abstract Recently XENON1T Collaboration announced that they observed some excess in the electron recoil energy around a 2–3 keV. We show that this excess can be interpreted as exothermic scattering of excited dark matter on atomic electron through dark photon exchange. We consider DM models with local dark U ( 1 ) gauge symmetry that is spontaneously broken into its Z 2 subgroup by Krauss-Wilczek mechanism. In order to explain the XENON1T excess with the correct DM thermal relic density within freeze-out scenario, all the particles in the dark sector should be light enough, namely ∼ O ( 100 ) MeV for scalar DM and ∼ O ( 1 − 10 ) MeV for fermion DM cases. And even lighter dark Higgs ϕ plays an important role in the DM relic density calculation: X X † → Z ′ ϕ for scalar DM (X) and χ χ ¯ → ϕ ϕ for fermion DM (χ) assuming m Z ′ > m χ . Both of them are in the p-wave annihilation, and one can easily evade stringent bounds from Planck data on CMB on the s-wave annihilations, assuming other dangerous s-wave annihilations are kinematically forbidden.

中文翻译：

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局部 Z2 DM 模型中的 XENON1T 过量，带有浅色扇区

摘要 最近 XENON1T Collaboration 宣布他们观察到电子反冲能量在 2-3 keV 附近有一些过剩。我们表明，这种过量可以解释为激发暗物质通过暗光子交换在原子电子上的放热散射。我们考虑具有局部暗 U ( 1 ) 规范对称性的 DM 模型，该对称性通过 Krauss-Wilczek 机制自发地分解为其 Z 2 子群。为了在冻结场景中用正确的 DM 热遗物密度解释 XENON1T 过量，暗区中的所有粒子都应该足够轻，即标量 DM 为 ~ O ( 100 ) MeV 和 ~ O ( 1 − 10 ) MeV 用于费米子 DM 案例。甚至更亮的暗希格斯 ϕ 在 DM 遗迹密度计算中也起着重要作用：XX † → Z ′ ϕ 对于标量 DM (X) 和 χ χ ¯ → ϕ ϕ 对于费米子 DM (χ)，假设 m Z ′ > m χ 。