Enhancing The MIGDAL Experiment's Sensitivity in the Low Energy Regime Relevant to Dark Matter Searches

在过去的几年里，阿卡迪·米格达尔（Arkady Migdal）在20世纪30年代末提出的一个模糊的量子力学预测彻底改变了对暗物质（DM）的研究。米格达尔效应已被引用，仅基于理论论据，以提高世界领先的DM实验的DM质量灵敏度2个数量级。该效应预测，原子核受到一个小的“踢”会导致原子电子的发射。当弹射来自非常轻的DM粒子时，反冲核沉积在探测器中的能量太小而无法检测到，但伴随的电子发射是可以检测到的。然而，在这一制度中没有观察到这种影响，这就对这些解释的有效性提出了质疑。考虑到米格达尔效应对DM检测的潜在影响，非常需要对该效应进行实验验证。该奖励将用于对DM搜索中感兴趣的一些原子进行明确的米格达尔效应检测。该方法利用了PI小组在开发探测器成像和解析低能粒子轨迹方面的最新进展。有了这种能力，可以通过重建从共同相互作用点发散的电子和核反冲轨迹来清楚地识别密达尔事件。作为MIGDAL国际合作的一员，PI将参与在英国一个特别设计的设施中检测效应的实验。基于第一次探测的详细研究将用于限制理论预测的能量高于DM实验中所利用的能量。新墨西哥大学正在开发将搜索范围扩大到较低能量所需的新型探测器，如果成功，将在该项目的第二阶段部署。该项目将训练本科生和研究生参与实验的各个方面。这将包括设计、测试和操作小型桌面探测器的实践经验，以及开发新的图像处理技术来模拟和分析数据。这个项目将使用Migdal效应评估的有效性设置暗物质(DM)限制通过探测和研究它在中子诱发核反冲原子对DM目标。它利用最新进展在π的小组展示高空间分辨率和高信噪比的低能量电离跟踪成像光学time-projection室(OTPC),使粒子识别和重建沿轨道运动的方向。利用这种能力，通过重建从相互作用点发散的电子和核反冲轨迹，可以清楚地识别出Migdal事件的拓扑结构。这些初步发现是欧洲资助的MIGDAL实验的基础，该实验将于秋季开始。该奖项将为积极参与实验的所有阶段提供支持，从数据采集到模拟和分析。该项目的一个关键目标是扩大对低能量的搜索，接近DM感兴趣的那些。这将涉及开发新的图像处理技术和具有低能量状态所需的精致空间分辨率的新型负离子OTPC。如果成功，这项技术将在MIGDAL试验的第二阶段实施。该奖项还将在越来越罕见的小规模实验中为各种各样的本科生和研究生提供培训和广泛的研究经验。凭借其新颖的功能，NID OTPC有望影响科学领域的广泛应用。其中包括x射线偏振测量、暗光子和双β搜索、罕见的核衰变、低背景α和中子测量等。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Over the past few years, an obscure quantum mechanical prediction made by Arkady Migdal in the late 1930’s has revolutionized the search for dark matter (DM). The Migdal effect has been invoked, based on theoretical arguments alone, to improve the DM mass-sensitivity of the world-leading DM experiment by 2 orders of magnitude. The effect predicts that an atomic nucleus receiving a small “kick” can result in the emission of an atomic electron. When the kick is from very light DM particles, the energy deposited in the detector by the recoiling nucleus is too small to detect, but the accompanying electron emission is detectable. The effect, however, has not been observed in this regime, raising questions on the validity of these interpretations. Given the potential impact of the Migdal effect on DM detection, an experimental verification of the effect is very much needed. This award will be used to make an unambiguous detection of the Migdal effect for a number of atoms of interest for DM searches. The method leverages recent progress in the PI’s group on developing detectors to image and resolve low energy particle tracks. With this capability, a Migdal event can be clearly identified by reconstructing the electron and nuclear recoil tracks diverging from a common interaction point. As a member of the international MIGDAL collaboration, the PI will participate in experiments to detect the effect at a specially designed facility in the UK. The detailed studies based on the first detection will be used to constrain theoretical predictions at energies above those being exploited in DM experiments. Novel detectors needed to extend the search to lower energies are being developed at UNM and, if successful, will be deployed in the second phase of this project. The project will train and involve undergraduate and graduate students in all aspects of the experiment. This will include hands-on experience in designing, testing and operating small table-top detectors and developing novel image processing techniques to simulate and analyze the data. This project will evaluate the validity of using the Migdal effect for setting dark matter (DM) limits by detecting and studying it in neutron-induced nuclear recoils in target atoms of interest for DM. It leverages recent progress in the PI’s group demonstrating high spatial resolution and high signal-to-noise imaging of low energy ionization tracks in an optical time-projection chamber (OTPC), which enables particle identification and reconstruction of its direction of motion along the track. With this capability, the Migdal event topology can be clearly identified by reconstructing the electron and nuclear recoil tracks diverging from the interaction point. These preliminary findings are the basis of a funded European MIGDAL experiment to begin in the Fall. This award will provide support to actively participate in all phases of the experiment, from data taking to simulations and analysis. A key goal of the project is to expand the search to lower energies, approaching those of interest to DM. This will involve developing novel image processing techniques and a novel negative ion OTPC with the exquisite spatial resolution needed for the low energy regime. If successful, this technology will be implemented in the second phase of the MIGDAL experiment. This award will also support training and a wide range of research experience to a diverse set of undergraduates and graduate students in increasingly rare small-scale experiments. With its novel capabilities, the NID OTPC promises to impact a broad range of applications across the sciences. These include X-ray polarimetry, dark-photon and double-beta searches, rare nuclear decays, low background alpha and neutron measurements and others.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.