发表机构
Shanghai Jiao Tong University（上海交通大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究基于DarkSHINE实验模拟，在正电子打固定靶方案中利用额外湮灭产生道搜寻不可见衰变暗光子，将排除限较电子打固定靶方案提高约两个数量级。
AI 中文摘要
我们基于DarkSHINE实验模拟设置，对正电子打固定靶（POT）方案中不可见衰变暗光子（$A^{\prime}$）的搜寻进行了前瞻性研究。在正电子打固定靶方案中，除了与电子打固定靶方案类似的轫致辐射产生过程外，还存在两种通过核外电子湮灭产生暗光子的额外产生道：非共振t道（$e^+e^-N \to \gamma A^{\prime}N$）和共振s道（$e^+e^-N \to A^{\prime}N$）。基于8 GeV正电子束、$3 \times 10^{14}$个POT事件的Geant4全探测器模拟，我们开发了一种利用缺失能量和动量特征的分析策略，在针对这些产生道优化的三个正交信号区域内进行搜寻。结果表明，暗光子产生的额外湮灭道提高了暗光子不可见衰变的搜寻灵敏度，与电子打固定靶（EOT）方案中的现有约束相比，排除限提高了约两个数量级，尤其是在质心系能量阈值附近。
英文摘要
We perform the prospective study on searching for invisibly decayed dark photons ($A^{\prime}$) in positron-on-fixed-target (POT) scheme with the DarkSHINE experiment simulation setup. In the positron-on-fixed-target scheme, two additional production channels of dark photons via annihilation with extranuclear electrons are present: non-resonant t-channel ($e^+e^-N \to γA^{\prime}N$) and resonant s-channel ($e^+e^-N \to A^{\prime}N$), alongside bremsstrahlung emission similar to electron-on-fixed-target scheme. Based on a GEANT4 full detector simulation of an 8 GeV positron beam with $3 \times 10^{14}$ POT events, we developed an analysis strategy using missing energy and momentum signatures across three orthogonal signal regions optimized for these channels. Our results indicate that the additional annihilation channels of dark photon production enhance the dark photon invisible decay search sensitivity, improving the exclusion limits by approximately two orders of magnitude compared to previous constraints in the electron-on-fixed target (EOT) scheme, particularly near the center-of-mass energy threshold for annihilation production of dark photons.
