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的进展，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？什么是群众等级制度？中微子振荡违反CP对称性吗？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。它的值设置了解决质量层次和搜索CP破坏所需的实验的规模。此外，13相对于其他混合角的大小可能有助于了解这些角的起源和中微子质量的来源。由芝加哥大学、哥伦比亚大学和巴纳德学院提出的一项建议是，为双中微子振荡实验建造外μ子否决和标记系统。实验的目标是测量13，其灵敏度比当前的最佳极限高出近一个数量级。否决系统是用来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。“双雷兹”实验将在法国雷兹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，宇宙成因背景是反应堆实验的一个严重问题。双重否定实验使用两部分，内部-外部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权，一个放置在探测器上方的大面积计数器系统。除了提供显著的背景抑制外，外层否决有望成为研究个体背景的有力工具，特别是9 Li背景，这是占主导地位的背景系统不确定性。至于该项目的更广泛影响，如果双π z实验证明13是非零的，则对CP破坏的搜索将特别引人注目。中微子扇区的CP破坏可能最终有助于解释宇宙中通过轻子生成的重子-反重子不对称性。在中微子区观测到任何CP破坏都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.