Understanding neutrino interactions and oscillations with off-axis neutrino beams

解释在早期宇宙中观测到的物质相对于反物质的过剩是物理学中最大的问题之一。中微子振荡可以违反CP对称，其程度可能大到足以产生这种过剩。理解中微子振荡是理解我们今天所看到的宇宙的重要一步。超级神冈探测器将使用一个20万吨的水切伦科夫探测器以前所未有的统计精度测量中微子振荡。现在的挑战是如何减小超神冈的系统不确定度，以确保其振荡测量的成功。解决这个挑战是我奖学金的重点。在长基线振荡实验中，主要的系统分类是由于很难将探测器中观察到的东西与中微子能量联系起来。E61实验被设计用来测量在J-PARC中微子束轴的一定角度范围内的中微子相互作用。中微子束的峰值能量随着离轴角的增加而减少，这使得E61可以直接将中微子能量与探测器中所看到的联系起来。这个链接使E61能够在中微子能量和探测器观察到的特征之间产生数据驱动的映射，显著降低与此相关的系统不确定性。E61方法需要详细了解E61探测器，特别是探测器的基准体积。为了实现这一点，我将为E61探测器制作一个光学校准系统，该系统将映射探测器体积并测量探测器对已知信号的响应。该系统将在探测器内部署校准源和高分辨率相机，以建立完整设备的3D模型，对探测器的响应和几何形状进行现场测量，而不是依赖于其中一个的非原位测量来计算另一个。这将采用分阶段的方法进行开发，在E61测试光束实验中安装一个原型系统。样机将为整个校准系统提供必要的反馈，而测试光束将为水切伦科夫探测器的校准提供有价值的物理数据。这项研究将以两种新的方式解决中微子振荡物理学中的关键挑战：使用离轴光束来理解中微子相互作用和一种新的校准系统来理解水切伦科夫探测器。这将是世界上最灵敏的中微子振荡CP违逆搜索。

Explaining the observed excess of matter compared to antimatter in the early universe is one of the biggest questions in physics. Neutrino oscillations can violate the CP symmetry, potentially by an amount large enough to produce this excess. Understanding neutrino oscillations is an essential step to understanding the universe we see today.Hyper-Kamiokande will use a 200-kiloton water Cherenkov detector to measure neutrino oscillations with unprecedented statistical precision. The challenge now is to reduce the systematic uncertainties of Hyper-Kamiokande to ensure the success of its oscillation measurements. Addressing this challenge is the focus of my fellowship.The dominant systematics in long-baseline oscillation experiments are due to the difficulty in relating what is observed in the detector to the neutrino energy. The E61 experiment has been designed to measure neutrino interactions over a range of angles off the J-PARC neutrino beam axis. The peak energy of the neutrino beam decreases as the off-axis angle increases, allowing E61 to directly relate neutrino energy to what is seen in the detector. This link enables E61 to produce a data-driven mapping between neutrino energy and the signatures observed in the detector, significantly reducing the systematic uncertainty associated with this.The E61 method requires a detailed understanding of the E61 detector, in particular the detector fiducial volume. To achieve this I will produce an optical calibration system for the E61 detector that will both map the detector volume and measure the detector response to a known signal. The system will deploy calibration sources and high-resolution cameras within the detector to build a 3D model of the full apparatus, producing an in-situ measurement of both the detector response and geometry, rather than relying on ex-situ measurements of one to calculate the other. This will be developed using a staged approach, with a prototype system installed in the E61 test beam experiment. The prototype will provide essential feedback for the full calibration system, whiile the test beam will provide valuable physics data for the calibration of water Cherenkov detectors.The research that this fellowship enables will address the key challenges in neutrino oscillation physics in two new ways: the use of off-axis beams to understand neutrino interactions and a novel calibration system to understand water Cherenkov detectors. Together these will produce the world's most sensitive search for CP violation in neutrino oscillations.