Collaborative Research: PM: RUI: Searches for Ultralight Bosonic Dark Matter with Atomic Magnetometer Networks

天体物理学观测表明，宇宙中高达85%的物质与构成我们日常世界的物质不同。所谓的暗物质是什么？这个问题的答案仍然是个谜。一种可能性是暗物质可能以大尺度结构（地球大小的许多倍）的形式与普通物质弱耦合。另一种可能性是暗物质可能以不同强度的波的形式存在。如果这样的结构或波穿过地球，它们可能会与原子相互作用，造成类似磁场的影响。这笔拨款将为三所本科院校——加州州立大学东湾分校、奥伯林学院和巴克内尔大学——提供支持，让它们与一个国际团队合作，寻找这种暗物质。寻找奇异物理的全球光磁力计网络（GNOME）是世界上15个机构的合作，这些机构已经建造了能够探测来自暗物质的这种信号的精密原子磁力计。来自磁力计网络的数据被分析，以寻找表明地球穿过暗物质结构或波的相关性。主要研究人员将与本科生合作，为网络开发更灵敏的探测器，分析网络数据，并与全球合作探测暗物质。这些测量将深入了解暗物质的可能形式，并使我们更好地了解宇宙的构成，同时为下一代科学家提供重要的研究经验和培训。一个很好的暗物质候选者包括超轻玻色子，如轴子、类轴子粒子（ALPs）或质量非常低（远小于1ev）的隐藏光子。超轻玻色子场可以形成稳定的宏观构型，如拓扑缺陷或玻色子星，例如，由于自相互作用。即使没有这种效应，玻色子暗物质场也表现出随机波动。此外，灾难性的天体物理事件可能会产生奇异的超轻玻色子场的强烈爆发。在任何一种情况下，当超轻玻色子场穿过地球时，地面探测器将见证瞬态事件，而不是沐浴在均匀的通量中。搜索奇异物理的全球光磁强计网络（GNOME）是一个由十几台时间同步的光原子磁强计组成的网络，用于搜索由于与超轻玻色子场的自旋依赖相互作用而对瞬态信号敏感的相关信号。GNOME磁力计具有多层磁屏蔽，可以减少外部磁噪声，但允许大多数类型的玻色子暗物质在不损失灵敏度的情况下穿透内部。一个明显的例外是隐藏的光子，它们的信号可以通过屏蔽大大减弱。为了寻找隐藏的光子暗物质，主要研究人员和本科生研究人员将基于GNOME架构构建一个新的无屏蔽磁强计网络，该网络位于磁场安静的环境中。提出的实验将探索描述超轻玻色子场的大范围未探索的参数空间。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。

Astrophysical observations indicate that up to 85% of the matter in the universe is unlike the matter that makes up our everyday world. What is this so-called dark matter? The answer to that question remains a mystery. One possibility is that dark matter could be in the form of large-scale structures (many times the size of the Earth) that couple weakly to ordinary matter. Another possibility is that the dark matter could be in the form of waves of varying intensity. If such structures or waves were to pass through the Earth they might interact with atoms and cause effects similar to those from a magnetic field. This grant will provide support for three undergraduate institutions, California State University – East Bay, Oberlin College, and Bucknell University, to work with an international team to search for dark matter of this kind. The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a collaboration of fifteen institutions throughout the world that have constructed precision atomic magnetometers that are capable of detecting such signals from dark matter. The data from the magnetometer network are analyzed to look for correlations that would indicate the Earth’s passage through dark matter structures or waves. The principal investigators will work with undergraduate students to develop more sensitive detectors for the network, analyze the network data, and work with the worldwide collaboration to detect dark matter. These measurements will give insight into the possible forms of dark matter and lead to a better understanding of the makeup of our universe while providing crucial research experience and training for the next generation of scientists. A well-motivated candidate for dark matter consists of ultralight bosons such as axions, axion-like particles (ALPs), or hidden photons with very low mass (much less than 1 eV). Ultralight bosonic fields can form stable, macroscopic configurations such as topological defects or boson stars due to, for example, self-interactions. Even in the absence of such effects, bosonic dark matter fields exhibit stochastic fluctuations. Additionally, it is possible that cataclysmic astrophysical events could produce intense bursts of exotic ultralight bosonic fields. In any of these scenarios, instead of being bathed in a uniform flux, terrestrial detectors will witness transient events when ultralight bosonic fields pass through Earth. The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a network of more than a dozen time-synchronized optical atomic magnetometers searching for correlated signals that is sensitive to transient signals due to spin-dependent interactions with ultralight bosonic fields. GNOME magnetometers have multi-layer magnetic shields that reduce external magnetic noise but allow most types of bosonic dark matter to penetrate within with no loss of sensitivity. A prominent exception is hidden photons, whose signals can be significantly reduced by shielding. To search for hidden photon dark matter, the principal investigators and undergraduate researchers will construct a new network of unshielded magnetometers, based on the GNOME architecture, located in magnetically quiet environments. The proposed experiments will probe a wide range of unexplored parameter space describing ultralight bosonic fields.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.