We propose that the nearly massless dark photons produced from the annihilation of keV dark fermions in the Galaxy can induce the excess of electron recoil events recently observed in the XENON1T experiment. The minimal model for this is the extension of a $U(1)_{X}$ gauge symmetry, under which the dark photon couples to both dark and visible matter currents. We find that the best-fit parameters of the dark sector are compatible with the most stringent constraints from stellar cooling. We also show that in the freeze-out scenario, the dark fermions can explain the anomaly while contributing $\gtrsim 1\%$ of the DM relic density.

中文翻译：

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来自 XENON1T 过剩的简单暗扇区的证据

我们提出，由银河系中 keV 暗费米子湮灭产生的几乎无质量的暗光子可以诱发最近在 XENON1T 实验中观察到的过量电子反冲事件。对此的最小模型是 $U(1)_{X}$ 规范对称性的扩展，在该对称性下，暗光子耦合到暗物质流和可见物质流。我们发现暗区的最佳拟合参数与恒星冷却的最严格限制兼容。我们还表明，在冻结场景中，暗费米子可以解释异常，同时贡献 DM 遗迹密度的 $\gtrsim 1\%$。