LZ 248 keV 事件视角下的银河系高速暗物质晕
The high-velocity dark matter halo of the Milky Way in light of the LZ 248 keV event
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中文总结 AI 辅助
本研究利用IllustrisTNG和FIRE模拟的银河系类似体，重新评估了LZ 248 keV事件解释中暗物质速度分布高速尾部的不确定性，发现最大速度中位数接近SHM值，且暗物质晕的各向异性和共转不降低该最大速度。
中文摘要 AI 辅助
直接探测实验中高能核反冲事件的解释可能敏感地依赖于银河系暗物质速度分布中了解甚少的高速尾部。这一事实最近因LZ实验观测到的一个反常核反冲事件（$E_R\approx248~\mathrm{keV}$）而受到更密切的关注。如果将该事件解释为由暗物质引起的反冲，那么许多模型的运动学约束意味着该粒子必须来自高速尾部。在此，我们利用IllustrisTNG和FIRE模拟中的银河系类似体重新评估了这一天体物理不确定性。我们发现，在事件被观测到的6月16日，实验室系中暗物质的最大速度为$792.7^{+82.9}_{-95.6}\\,\mathrm{km/s}$（跨模拟的中位数和95%包含区间），其中位数非常接近基准SHM值。对三维速度分布尾部的建模因这些模拟暗物质晕是各向异性的且通常被看到与重子盘同向旋转而变得复杂。然而，我们发现这并未降低实验室系中暗物质的最大速度，因为近似高斯分布的方位角速度分布因这种共转而呈负偏态，而非被其平移。我们以非弹性暗物质解释LZ事件的背景来说明这些结果。
英文摘要
The interpretation of high-energy nuclear recoil events in direct-detection experiments can depend sensitively on the poorly understood high-speed tail of the Galactic dark matter velocity distribution. This fact has been brought into sharper focus recently by an anomalous nuclear-recoil event at $E_R\approx248~\mathrm{keV}$ observed by the LZ experiment. If interpreted as caused by a dark-matter-induced recoil, kinematic constraints on many models imply this particle would have to emerge from the high-speed tail. Here, we re-assess this astrophysical uncertainty using Milky Way analogues from the IllustrisTNG and FIRE simulations. We find that the maximum laboratory-frame DM speed on June 16, when the event was observed, is $792.7^{+82.9}_{-95.6}\, \mathrm{km/s}$ (median and 95\% containment across simulations), with a median very close to the fiducial SHM value. Modelling the tail of the velocity distribution in three dimensions is complicated by the fact that these simulated dark matter halos are anisotropic and are generically seen to spin in the same direction as the baryonic disk. However, we find that this does not reduce the maximum laboratory-frame DM speed because the approximately Gaussian azimuthal velocity distribution is negatively skewed by this co-rotation, rather than shifted by it. We illustrate these results in the context of an inelastic dark matter interpretation of the LZ event.
发表机构
- University of Sydney（悉尼大学）
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