RUI: Neutrino Scattering Experiments at the Spallation Neutron Source

在所有已知的基本粒子中，中微子的探测难度很大，因为它们与其他形式的物质相互作用的可能性很小。通常涉及大型（吨或多吨）探测器。相干弹性中微子核散射（CEvNS）是一种早在40多年前就被预测到的中微子相互作用机制，但直到最近才被相干合作使用铯-碘化探测器观测到。通过CEvNS探测到中微子的概率比任何已知的中微子与物质相互作用的模式都要大得多，但是产生的信号很微妙，很难分离，并且依赖于探测器的元素组成。测量这些相互作用有助于限制逃避中微子的许多未知性质，并有助于改进粒子相互作用的基本理论。该提案支持北卡罗来纳中央大学（NCCU）中微子组继续参与相干协作活动，包括部署多吨碘化钠探测器和开发和部署锗探测器阵列。全系列探测器（碘化铯、碘化钠和锗）将允许对描述CEvNS相互作用的理论进行强有力的测试。NCCU是一所授予硕士学位，主要是本科生的历史黑人学院或大学（HBCU），其中大多数学生是非洲裔美国人或西班牙裔美国人。该奖项将支持北大学生从事前沿物理研究。该奖项还支持国立中央大学望远镜团队，中微子组的学生为当地的户外天文学项目做出贡献，并为高中STEM项目和公众提供关于使用核物理技术分析文物的讲座。此外，计划亦会与香港中文大学克莱门特早期学院高中的学生合作，参与建造和部署包括辐射探测器在内的环境监测仪器。CEvNS相互作用是与超新星动力学相关的最大横截面之一，在核心坍缩过程中起着重要作用，因为在标准模型中，CEvNS横截面被预测为与目标核中子数n的平方近似成比例，这种n的平方依赖实际上是相互作用相干性质的标志，表明目标核作为一个整体而不是单个中子或质子反冲。为了充分探测CEvNS相互作用，必须测试一系列的原子核。该提案使NCCU能够为部署多吨NaI探测器阵列做出贡献，并开发低背景，低阈值，p型点接触锗探测器的屏蔽阵列。除了光谱n平方的依赖性外，CEvNS在Ge中的精确测量将导致有关核形状因子的信息。奇质子核23-钠的CEvNS测量有望对相互作用的轴向矢量贡献敏感。中微子散射截面的测量引起了物理界广泛的兴趣。有了一个很好的预测标准模型横截面，偏离期望值成为非标准中微子相互作用的探针，并可能对轻介质粒子施加限制。例如，CEvNS与太阳和大气中微子的相互作用是直接搜索暗物质弱相互作用大质量粒子（WIMP）的不可简化的背景。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。

Of all known elementary particles, neutrinos stand out for the difficulty involved in their detection, a result of their tiny probability of interaction with other forms of matter. Large (ton or multi-ton) detectors are typically involved. Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) is a mechanism of neutrino interaction predicted more than four decades ago, but only recently observed by the COHERENT collaboration using a Cesium-Iodide detector. The probability of neutrino detection via CEvNS is much larger than for any other known mode of neutrino interaction with matter, but the signals generated are subtle, hard to isolate, and dependent on the elemental composition of the detector. Measuring these interactions helps to constrain the many unknown properties of the evasive neutrino and contributes to the refinement of the underlying theories of particle interactions. This proposal supports the North Carolina Central University (NCCU) neutrino group to continue its participation in the COHERENT Collaboration activities including the deployment of a multi-ton Sodium Iodide detector and the development and deployment of a Germanium detector array. The full range of detectors (Cesium Iodide, Sodium Iodide, and Germanium) will allow for a robust test of the theory describing the CEvNS interaction. NCCU is a master’s granting, primarily undergraduate Historically Black College or University (HBCU) in which the majority of students participating are African-American or Hispanic-American. This award will support the engagement of NCCU students in forefront physics research. The award also supports the NCCU Telescope Team in which students from the neutrino group contribute to local Outdoor Astronomy programs, and give lectures to high-school STEM programs and the public on the use of nuclear physics techniques for analysis of cultural artifacts. In addition, the PI will initiate activities with the Clement Early College High School students at NCCU to participate in the building and deploying of environmental monitoring instruments including radiation detectors. The CEvNS interaction is one of the largest cross sections relevant to supernova dynamics and plays an important role in core collapse processes because the CEvNS cross-section is predicted, in the Standard Model, to scale approximately with the square of the target nucleus neutron number, N. This N-squared dependence is in fact the signature of the coherent nature of the interaction, indicating that the target nucleus recoils as a whole rather than as an individual neutron or proton. In order to fully probe the CEvNS interaction, a range of nuclei must be tested. This proposal enables NCCU to contribute to the deployment of a multi-ton NaI detector array and to develop a shielded array of low-background, low-threshold, p-type point contact Ge detectors. In addition to the spectral N-squared dependence, the precision CEvNS measurements in Ge will lead to information on nuclear form factors. CEvNS measurement in the odd-proton nucleus 23-Sodium will hopefully be sensitive to axial vector contributions to the interaction. The measurements of neutrino scattering cross sections are of interest to a broad range of physics communities. With a well-predicted Standard Model cross section, deviations from the expected values become a probe of non-standard neutrino interactions and may put limits on light mediator particles. The CEvNS interaction with solar and atmospheric neutrinos, for example, is an irreducible background to direct dark matter weakly interacting massive particles (WIMP) searches.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.