标题： 固定靶配置下的$t$通道暗光子搜索 显示英文标题

标题： $t$-Channel Dark Photon Search at Fixed-Target Configurations

摘要： 在这项工作中，我们研究了电子固定靶实验中不可见暗光子（$A'$）探测的$t$-通道（$e^+ e^- \to \gamma A'$）贡献。为了说明这一点，我们同时考虑了 Belle II 中消失的正电子径迹信号和 NA64$e$中的大缺失能量搜索。 When the dark photon has a narrow decay width, the $t$-channel process can dominate over its $s$-channel and bremsstrahlung counterparts around $m_{A'} \simeq 60\,\rm{MeV}$ ($m_{A'} \simeq 200\,\rm{MeV}$) for Belle II (NA64$e$), to enhance the corresponding sensitivity on the kinetic mixing parameter $\epsilon$ by a factor of up to approximately 3 (1.3). For Belle II, we further perform a multi-bin analysis with the spectrum information to better separate the background and signal channels for significant improvement of the sensitivity. 显示英文摘要

摘要： In this work, we investigate the $t$-channel ($e^+ e^- \to \gamma A'$) contribution to the invisible dark photon ($A'$) searches at the electron fixed-target configurations. For illustration, we consider both the disappearing positron track signature at Belle II and the large missing energy search at NA64$e$. When the dark photon has a narrow decay width, the $t$-channel process can dominate over its $s$-channel and bremsstrahlung counterparts around $m_{A'} \simeq 60\,\rm{MeV}$ ($m_{A'} \simeq 200\,\rm{MeV}$) for Belle II (NA64$e$), to enhance the corresponding sensitivity on the kinetic mixing parameter $\epsilon$ by a factor of up to approximately 3 (1.3). For Belle II, we further perform a multi-bin analysis with the spectrum information to better separate the background and signal channels for significant improvement of the sensitivity.