$q_1-q_2$ 规范扩展中的强子型非弹性 freeze-in 暗物质与高能 LZ 事件
Hadrophilic inelastic freeze-in dark matter in $q_1-q_2$ gauge extension and the high energy LZ event
AI总结：
本文在强子型 $q_1-q_2$ 规范扩展中提出放热暗物质散射，通过 freeze-in 机制和 $Z'$ 媒介子同时解释 LZ 高能事件与 relic 密度，并规避间接探测约束。
AI中文摘要：
LZ 合作组最近在核反冲能量 $248\pm23\pm23$ keV 处观测到单个事件，这促使暗物质（DM）模型构建者探索新的物理解释。虽然现有文献大多通过 TeV 尺度暗物质的吸热散射来解释该事件，但多数模型中偏好的暗物质相互作用强度与间接探测约束存在冲突。为规避这一问题，本文在强子型 $q_1-q_2$ 规范扩展框架下探索放热暗物质散射，其中新的 $Z'$ 玻色子作为与暗 sector 的媒介子。由于媒介子与中微子、$W$、$\tau$ 和 $b$ 夸克没有树级耦合，这可以自然地避开间接搜索。我们考虑在低再加热温度下的 freeze-in 产生机制，以在早期宇宙中填充暗物质，其耦合强度相对热 freeze-out 情景更小。我们确定了能够同时解释观测到的 relic 密度和 LZ 事件的 $Z'$ 参数空间，并讨论了来自味道混合和味改变中性流（FCNC）的相关约束。
英文摘要：
The recent observation of a single event at nuclear recoil energy $248\pm23\pm23$ keV by the LZ collaboration has prompted dark matter (DM) model builders to explore new physics explanations. While most of the existing literature invokes an endothermic scattering by a TeV-scale DM to explain the event, the favored DM interaction strength is in tension with the indirect detection constraints for most of the models. To evade this, this work explores exothermic DM scattering in a hadrophilic $q_1-q_2$ gauge extension setup with a new $Z'$ boson as a mediator to the dark sector. This can naturally escape the indirect searches in the absence of tree-level coupling of the mediator to neutrinos, $W,τ$, and $b$ quark. We consider freeze-in production at a low reheating temperature to populate DM in the early universe, with a comparatively smaller coupling than the thermal freeze-out scenario. We identify the $Z'$ parameter space that can explain the observed relic density and LZ event simultaneously. We also discuss the relevant constraints coming from flavor mixing and FCNC.
