The search for a dark photon produced at $e^+e^-$ colliders in the forward region, which subsequently decays into an excited and a ground state dark matter, is discussed. The excited dark matter decays into a pair of visible charged particles and a normal dark matter after traveling some distance. The visible decay products can be recorded by an emulsion detector, placed around the main $e^+e^-$ detector. This setup can not only explore new parameter regions not reached before, but also re-open some regions thought to be excluded by previous experimental data. The physics potential of such a detector around BESIII and Belle-II is presented.

中文翻译：

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在正负电子对撞机周围寻找暗光子和暗物质特征

讨论了在前部区域的 $e^+e^-$ 对撞机处产生的暗光子的搜索，该暗光子随后衰变成激发态和基态暗物质。被激发的暗物质在移动一段距离后衰变成一对可见的带电粒子和一个正常的暗物质。可见的衰变产物可以由放置在主 $e^+e^-$ 探测器周围的乳液探测器记录。这种设置不仅可以探索以前未达到的新参数区域，还可以重新打开一些被先前实验数据排除的区域。介绍了这种探测器在 BESIII 和 Belle-II 周围的物理潜力。