发表机构
Sam Houston State University; The University of Melbourne（萨姆休斯顿州立大学; 墨尔本大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
LZ实验在约250 keV处发现一个类核反冲事件，该研究提出放热非弹性暗物质可解释此事件，利用高能边带约束偏好轻暗物质，预测未来曝光的信号事件数，现有其他实验数据可检验该解释。
AI 中文摘要
LZ实验已将其核反冲搜索扩展至270 keV，并在预期本底可忽略的区域报告了一个类核反冲事件LZ230616，其能量约为250 keV。我们表明，放热非弹性暗物质（环境暗态向下散射并将其质量分裂|δ|作为反冲能量释放）可自然地在该能量产生反冲峰，同时仍与较低能量处的零结果相符。我们的简单拟合未对质量施加约束，因为重候选粒子可将其峰隐藏在LZ的感兴趣区域之上。然而，我们证明，LZ用于本底验证的空高能边带不支持宽峰谱。因此，对于放热解释，更偏好由较轻暗物质与更大质量分裂产生的更锐峰。实现该情景需要宇宙学稳定态和一种轻子非亲和中介子。以观测到的一个事件归一化，我们预测在LZ预计的1000个活日曝光中约有4.5个信号事件，并表明现有XENONnT和PandaX-4T数据可在扩展分析窗口中检验该解释。
英文摘要
The LZ experiment has extended its nuclear-recoil search to 270 keV and reports a single nuclear-recoil-like event, LZ230616, at $\sim250$ keV, in a region with negligible expected background. We show that exothermic inelastic dark matter, in which the ambient dark state down-scatters and releases its mass splitting $|δ|$ as recoil energy, can naturally produce a recoil peak at this energy while remaining consistent with the null result at lower energies. Our simple fit leaves the mass unconstrained, because a heavy candidate can hide its peak above the LZ region-of-interest. However, we show that the empty high-energy sideband, which LZ uses for background validation, disfavors broadly peaked spectra. For an exothermic explanation, the sharper peaks produced by lighter dark matter with larger mass splittings are therefore preferred. Realizing this scenario requires cosmologically stable states and a leptophobic mediator. Normalizing to the one observed event, we predict $\simeq4.5$ signal events in LZ's projected 1000 live-day exposure, and show that existing XENONnT and PandaX-4T data could already test the interpretation in an extended analysis window.
Comments4 pages, 3 figures
