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

近年来，中微子混合的物理学取得了巨大的进步，但仍然存在几个关键问题：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？什么是群众等级制度？中微子振荡是否违背CP对称性？为什么夸克和中微子的混合矩阵如此不同？13的价值对这些问题中的每一个都至关重要。它的值设置了解析质量层次结构和搜索CP违规所需的实验的比例。此外，相对于其他混合角的13的大小可能给出这些混合角的起源和中微子质量的来源的见解。反应堆实验有望明确地确定13个混合角。这项由芝加哥大学、哥伦比亚大学和巴纳德学院提出的提案要求资金，为双Chooz中微子振荡实验建造外部Muon否决权和标记系统。这项实验的目标是测量13个灵敏度，几乎比目前的最佳极限高出一个数量级。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器元件，这对于实现实验的灵敏度目标至关重要。Double Chooz实验将使用法国Chooz核电站附近的两个探测器。由于反应堆反中微子的能量很少，宇宙成因背景对反应堆实验来说是一个严重的问题。Double Chooz实验使用了一个由内外两部分组成的否决权系统来减少和测量这些背景。该小组建议构建外部否决权，这是一个放置在探测器上方的大面积闪烁计数器系统。除了提供显著的背景抑制外，外部否决权有望成为研究个人背景的有力工具，特别是9Li背景，这是系统的主要背景不确定性。至于这个项目的更广泛影响，如果Double Chooz实验证明13是非零的，那么搜索CP违规将特别引人注目。中微子区域的CP破坏最终可能有助于解释宇宙中重子-反重子的不对称性。在中微子区域观测到的任何CP破坏都将是解开粒子物理学中最基本的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.