Construction of a Muon Tagging System for the Double Chooz Neutrino Experiment

近年来，中微子混合物理学取得了巨大进展，但仍存在几个关键问题：中微子混合矩阵中最后一个未测量的混合角13的值是多少？什么是大众等级制度？中微子振荡违反CP对称吗？为什么夸克和中微子的混合矩阵如此不同？13的值是这些问题的核心。它的值为解决质量层次和搜索CP违逆所需的实验设定了尺度。此外，13的大小相对于其他混合角可以让我们深入了解这些角的起源和中微子质量的来源。反应器实验有望明确地确定13混合角。这份由芝加哥大学、哥伦比亚大学和巴纳德学院共同提出的提案，要求资助构建双Chooz中微子振荡实验的外μ子否决和标记系统。实验的目标是测量13，其灵敏度几乎比目前的最佳极限高一个数量级。否决权系统是用于抑制背景和了解其系统不确定性的主要探测元件，这对于达到实验的灵敏度目标至关重要。双Chooz实验将在法国Chooz核电站附近使用两个探测器。由于反应堆反中微子的能量很少，宇宙起源背景是反应堆实验的一个严重问题。“双重选择实验”采用两部分的内外否决系统来减少和测量这些背景。这个小组建议建造外部否决，一个放置在探测器上方的大面积闪烁计数器系统。除了提供重要的背景抑制外，外部否决权有望成为研究个体背景的有力工具，特别是作为主要背景系统不确定性的9Li背景。至于这个项目更广泛的影响，如果Double Chooz实验证明13不为零，对CP违反的搜索将特别引人注目。中微子扇区的CP违逆可能最终有助于解释宇宙中重子-反重子的不对称性。在中微子扇区观察到任何CP违逆，将是粒子物理学中最基本问题之一的重要线索。

Recent years have seen enormous progress in the physics of neutrino mixing, but several critical questions remain: What is the value of 13, the last unmeasured mixing angle in the neutrino mixing matrix? What is the mass hierarchy? Do neutrino oscillations violate CP symmetry? Why are the quark and neutrino mixing matrices so different? The value of 13 is central to each of these questions. Its value sets the scale for experiments needed to resolve the mass hierarchy and to search for CP violation. In addition, the size of 13 with respect to the other mixing angles may give insights into the origin of these angles and source of neutrino mass. Reactor experiments hold the promise of unambiguously determining the 13 mixing angle.This proposal, from the University of Chicago, Columbia University and Barnard College, requests funds to construct the outer muon veto and tagging system for the Double Chooz neutrino oscillation experiment. The goal of the experiment is the measurement of 13 with almost an order-of-magnitude better sensitivity than the current best limit. The veto system is the main detector element used to suppress backgrounds and to understand their systematic uncertainties, which will be essential to reaching the experiment's sensitivity goal. The Double Chooz Experiment will use two detectors near the Chooz Nuclear Power Station in France. As a result of the few MeV energy of the reactor antineutrinos, cosmogenic backgrounds are a serious issue for reactor experiments. The Double Chooz Experiment uses a two-part, inner-outer veto system to reduce and measure these backgrounds. This group proposes to construct the outer veto, a large-area system of scintillating counters placed above the detector. In addition to providing significant background suppression, the outer veto is expected to be a powerful tool in studying individual backgrounds, particularly the 9Li background which is the dominant background systematic uncertainty.As for the Broader Impacts of this project, if the Double Chooz experiment demonstrates that 13 is nonzero, searches for CP violation will be particularly compelling. CP violation in the neutrino sector may ultimately help explain the baryon-antibaryon asymmetry in the universe through leptogenesis. Observation of any CP violation in the neutrino sector would be an important clue to one of the most fundamental questions in particle physics.