增强还是非弹性？判别LZ 248 keV事件的不同解释
Boosted or Inelastic? Discriminating Interpretations of the LZ 248 keV Event
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中文总结 AI 辅助
本文通过对比非弹性与增强暗物质两种机制，利用有效算符分析LZ实验248 keV事件，发现二者谱形可区分，少量额外事件即可判别，为暗物质模型提供鉴别途径。
中文摘要 AI 辅助
LUX-ZEPLIN实验报告了一个核反冲候选事件，其能量为$E_R = 248 \pm 23(\mathrm{stat}) \pm 23(\mathrm{sys})$~keV，在全局显著性为$2.6\sigma$的水平上不利于仅含背景的假设。该事件带来的困难不在于反冲能量本身，而在于低能区缺乏任何伴随的超出，因为晕暗物质的弹性散射会产生单调递减的谱，而提供所需的动量转移$q \simeq 246$~MeV已经要求$m_\chi \gtrsim 79$~GeV。我们将该事件与两种运动学上截然不同且能规避此限制的机制进行对比：吸热非弹性暗物质，其中质量劈裂$\delta \sim \mathcal{O}(100)$~keV禁止低能反冲；以及增强暗物质，其中轻的相对论性通量提供动量。我们对两种机制均采用相同的模型无关的标量-标量、赝标量-标量和赝标量-赝标量有效算符进行处理。这两种情景在谱上被证明是可区分的。对于每种算符，非弹性谱都位于观测能量附近，只有$6$--$17\\%$的事件低于150~keV；而增强谱则关键地依赖于算符：标量和赝标量-标量相互作用分别将$99\\%$和$92\\%$的事件置于150~keV以下，而赝标量-赝标量相互作用则将$75\\%$的事件置于该能量以上。因此，动量依赖性对于增强解释至关重要，但在非弹性情形中，它需与劈裂进行权衡，优选的$\delta$从$\mathcal{O}_{ss}$到$\mathcal{O}_{ps}$再到$\mathcal{O}_{pp}$单调递减。由于这两种情景在整个高能窗口内均存在差异，少量额外事件即可区分它们，从而使该问题在LZ完整曝光量下有望得到解决。
英文摘要
The LUX-ZEPLIN experiment has reported a single nuclear recoil candidate at $E_R = 248 \pm 23(\mathrm{stat}) \pm 23(\mathrm{sys})$~keV, disfavouring the background-only hypothesis at a global significance of $2.6σ$. The difficulty such an event poses is not the recoil energy itself but the absence of any accompanying excess at low energy as elastic scattering of halo dark matter yields a monotonically falling spectrum, and supplying the required momentum transfer $q \simeq 246$~MeV already demands $m_χ\gtrsim 79$~GeV. We confront the event with the two kinematically distinct mechanisms that evade this limitation, endothermic inelastic dark matter, in which a mass splitting $δ\sim \mathcal{O}(100)$~keV forbids low-energy recoils and boosted dark matter, in which a light relativistic flux supplies the momentum, treating both with the same model-independent scalar--scalar, pseudoscalar--scalar and pseudoscalar--pseudoscalar effective operators. The two scenarios prove spectrally distinguishable. The inelastic spectra sit near the observed energy for every operator, placing only $6$--$17\%$ of events below 150~keV, whereas the boosted spectra depend critically on the operator: the scalar and pseudoscalar--scalar interactions place $99\%$ and $92\%$ of their events below 150~keV, while the pseudoscalar--pseudoscalar interaction places $75\%$ above it. Momentum dependence is thus essential to the boosted interpretation, but in the inelastic case it trades against the splitting, the preferred $δ$ decreasing monotonically from $\mathcal{O}_{ss}$ to $\mathcal{O}_{ps}$ to $\mathcal{O}_{pp}$. Because the scenarios differ across the whole high-energy window, a handful of additional events would separate them, placing the question within reach of the full LZ exposure.
发表机构
- Indian Institute of Technology Goa（印度果阿理工学院）
- Indian Institute of Technology Hyderabad（印度海得拉巴理工学院）
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