古探测器探测暗物质的新方案
New Projections for Dark Matter Searches with Paleo-Detectors
摘要：
古探测器是一种寻找暗物质的实验技术。古探测器利用地球上深埋地下（$\gtrsim 5$ km）的天然岩石的小样本，积累来自$\mathcal{O}(1)$ Gyr的反冲核的核损伤轨迹，而不是操作吨级实时探测器来搜索DM引起的核反冲的传统方法。现代显微技术保证了在宏观样品中读出纳米分辨率的核损伤径迹的能力。由于它们的$\mathcal{O}(1)$陀螺积分时间，古探测器可以构成具有keV反冲能量阈值和100千吨-年暴露量的核反冲探测器。这种组合将允许古探测器探测低于常规直接探测实验的现有上限的DM-核子截面数量级。在这篇文章中，我们使用改进的背景建模和一种新的光谱分析技术，以更新的灵敏度预测古探测器。我们证明了灵敏度预测的鲁棒性（缺乏）辅助测量的样品的年龄和参数控制的背景，系统的背景的光谱形状的错误建模，和矿物样品的放射性纯度。具体来说，我们证明，即使在古探测器样品中的铀浓度是$10^{-8}$（每重量），许多数量级大于我们预期的最放射性纯的样品从超基性岩或海洋蒸发岩矿床，古探测器仍然可以探测DM-核子截面低于当前的限制。对于DM质量为$\lesssim 10$ GeV/ $c^2$的情况，在基于Xe的直接探测实验中，古探测器的灵敏度仍然可以一直达到传统的中微子底。
英文摘要：
Paleo-detectors are a proposed experimental technique to search for dark matter (DM). In lieu of the conventional approach of operating a tonne-scale real-time detector to search for DM-induced nuclear recoils, paleo-detectors take advantage of small samples of naturally occurring rocks on Earth that have been deep underground ($\gtrsim 5$ km), accumulating nuclear damage tracks from recoiling nuclei for $\mathcal{O}(1)$ Gyr. Modern microscopy techniques promise the capability to read out nuclear damage tracks with nanometer resolution in macroscopic samples. Thanks to their $\mathcal{O}(1)$ Gyr integration times, paleo-detectors could constitute nuclear recoil detectors with keV recoil energy thresholds and 100 kilotonne-yr exposures. This combination would allow paleo-detectors to probe DM-nucleon cross sections orders of magnitude below existing upper limits from conventional direct detection experiments. In this article, we use improved background modeling and a new spectral analysis technique to update the sensitivity forecast for paleo-detectors. We demonstrate the robustness of the sensitivity forecast to the (lack of) ancillary measurements of the age of the samples and the parameters controlling the backgrounds, systematic mismodeling of the spectral shape of the backgrounds, and the radiopurity of the mineral samples. Specifically, we demonstrate that even if the uranium concentration in paleo-detector samples is $10^{-8}$ (per weight), many orders of magnitude larger than what we expect in the most radiopure samples obtained from ultra basic rock or marine evaporite deposits, paleo-detectors could still probe DM-nucleon cross sections below current limits. For DM masses $\lesssim 10$ GeV/$c^2$, the sensitivity of paleo-detectors could still reach down all the way to the conventional neutrino floor in a Xe-based direct detection experiment.
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