We present a new mechanism for thermally produced dark matter, based on a semi-annihilation-like process, $\chi +\chi +\mathrm{SM}\to \chi +\mathrm{SM}$, with intriguing consequences for the properties of dark matter. First, its mass is low, $\lesssim 1\mathrm{GeV}$ (but $\gtrsim 5\mathrm{keV}$ to avoid structure-formation constraints). Second, it is strongly interacting, leading to kinetic equilibrium between the dark and visible sectors, avoiding the structure-formation problems of $\chi +\chi +\chi \to \chi +\chi$ models. Third, in the $3\to 2$ process, one dark matter particle is consumed, giving the standard-model particle a monoenergetic recoil. We show that this new scenario is presently allowed, which is surprising (perhaps a “minor miracle”). However, it can be systematically tested by novel analyses in present and near-term experiments. In particular, the Co-SIMP model for thermal-relic dark matter can explain the XENON1T excess.

中文翻译：

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强烈相互作用的暗物质的新冻结机制

我们提出了一种基于半-灭过程的热产生暗物质的新机制， $\chi +\chi +\mathrm{SM}\to \chi +\mathrm{SM}$，对暗物质的性质产生有趣的影响。首先，它的质量很低$\lesssim \mathrm{1个}\mathrm{GeV}$ （但 $\gtrsim 5\mathrm{keV}$以避免结构形成约束）。其次，它之间的相互作用很强，导致了暗区和可见区之间的动力学平衡，避免了结构的形成问题。$\chi +\chi +\chi \to \chi +\chi$楷模。第三，在$3\to 2$在此过程中，消耗了一个暗物质粒子，使标准模型粒子具有单能量反冲力。我们表明，目前允许这种新方案，这令人惊讶（也许是“次要奇迹”）。但是，可以通过当前和近期实验中的新颖分析来系统地对其进行测试。特别地，用于热遗物暗物质的Co-SIMP模型可以解释XENON1T的过量。