New Experiment Techniques For Neutrino Physics

在过去的二十年里，中微子物理学和宇宙学发生了两个显著的范式转变。关于中微子物理学，或者更准确地说，在中微子质量问题上，领域已经从发现转向精确。从太阳中微子、大气层中微子和反应堆中微子收集的测量结果确凿地表明，中微子改变了味道，因此质量非常小，但不是零。对这些振荡参数的测量现在正在几个百分点的水平上进行探索。几乎与此同时，观测宇宙学也进行了类似的相变，进行了精确的测量，提供了一种出色的宇宙观。对宇宙的能量、物质含量和演化的精确测量，现在可以对宇宙学模型进行详细的测试，而这些测试在十年前是无法获得的。研究人员终于到达了这样一个阶段，即由宇宙学确定的中微子质量与由核实验确定的中微子质量之间的直接比较成为可能。这些新的进展迫使该领域开发出突破中微子质量敏感度界限的技术。麻省理工学院的中微子小组正在领导一项名为Project 8的下一代中微子质量实验，该实验利用了一种全新的中微子质量测量方法。通过使用频率来测量能量，可以提取精致的光谱信息。这项合作证明了回旋辐射发射光谱(CRES)技术提取了从放射性气体中产生的电子的能量，并表明该技术也适用于氚β衰变。中微子质量的知识对科学界具有广泛的影响，特别是在核物理、粒子物理和宇宙学领域。CRES技术是一种通用的低能电子光谱技术，具有广泛的适用性。金属超导测辐射热计用于反冲探测也有广泛的应用，在核反应堆监测和直接暗物质探测方面有潜在的应用。这些课题已经并将继续得到物理学本科生的广泛支持和参与。目前，该合作正在扩展CRES技术，以建立一个新的贝塔衰变实验，提高中微子质量尺度的灵敏度。Project 8实验的目标是在90%的置信度下将中微子的质量灵敏度降低到40 mev/c^2。麻省理工学院中微子小组还在推动一项新技术，该技术旨在探测中微子相互作用中由相干弹性中微子核散射产生的低能量反冲。具体地说，他们正在开发阈值足够低的金属超导测辐射热计，以能够检测到反应堆中微子的相干散射。这项名为“跳跃”的新实验成果，在探索新物理，甚至核反应堆监测方面具有潜在的应用价值。该实验最近被批准部署在法国格勒诺布尔的ILL反应堆。这一奖励反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Two remarkable paradigm shifts have taken place over the past twenty years in neutrino physics and cosmology. With regard to neutrino physics, or more precisely on the question of neutrino mass, the field has shifted from discovery to precision. Measurements gathered from solar, atmospheric, and reactor neutrinos have shown conclusively that neutrinos change flavor and, as a consequence, have a very small but nonzero mass. The measurements on these oscillation parameters are now being probed at the few percent level. Almost concurrently, observational cosmology has made a similar phase transition into precision measurements, providing an outstanding view of the cosmos. Precision measurements on the energy and matter content and evolution of the universe now allow detailed tests of cosmological models that were simply unavailable even a decade ago. Investigators are finally reaching the stage in which direct comparisons between neutrino masses as determined by cosmology and as determined by nuclear experiments are possible. These new advances compel the field to develop techniques that push the boundaries of neutrino mass sensitivity. The Neutrino group at MIT is leading a next-generation neutrino mass experiment called Project 8 that utilizes an entirely new approach in neutrino mass measurements. By using frequency to measure energy, one can extract exquisite spectroscopic information. The collaboration has demonstrated that the Cyclotron Radiation Emission Spectroscopy (CRES) technique extracts the energy of electrons created from a radioactive gas and has shown that the technique also works on tritium beta decay. Knowledge of neutrino masses has broad implications for the scientific community, particularly in the fields of nuclear physics, particle physics, and cosmology. The CRES technique, being a general spectroscopic technique for low energy electrons, has broad applicability. The use of metallic superconducting bolometers for recoil detection also has broad reach, having potential applications in nuclear reactor monitoring and direct dark matter detection. These topics have and continue to draw broad support and engagement from undergraduate students in physics.The collaboration is now expanding the CRES technique to build a new beta decay experiment with improved sensitivity for the neutrino mass scale. The goal of the Project 8 experiment is to push the neutrino mass sensitivity down to 40 meV/c^2 at 90% confidence limit. The MIT Neutrino Group is also pushing a novel technology designed to detect low energy recoils created in neutrino interactions from coherent elastic neutrino nucleus scattering. Specifically, they are developing metallic superconducting bolometers with thresholds sufficiently low as to enable detection of coherent scattering from reactor neutrinos. The new experimental effort, Ricochet, has potential applications in searching for new physics and even nuclear reactor monitoring. The experiment has recently been approved to be deployed at the ILL reactor in Grenoble, France.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.