Search for Neutrinoless Double Beta Decay from the SNO+ Experiment

在过去的十年里，一些最令人兴奋的物理学出现在中微子物理学领域。萨德伯里中微子天文台（SNO）是最前沿的实验之一，位于加拿大安大略萨德伯里的SNOLAB地下科学实验室，是2015年诺贝尔物理学奖的获得者。牛津大学的SNO小组在解决“太阳中微子问题”方面发挥了主导作用，并首次清楚地证明中微子是以混合态存在的，这使得它们可以从一种类型“振荡”到另一种类型。在这个非常成功的项目之后，一个后续实验SNO+正在进行，其物理目标非常多样化和有趣。该项目的主要目标是灵敏地寻找一种非常罕见的过程，称为“无中微子双β衰变”。“对这一点的观察既可以确定中微子的绝对质量，也可以确定中微子作为自己的反粒子，这可能对我们理解宇宙中的物质/反物质不对称性产生重大影响。这一研究领域被认为在粒子物理学中具有极其重要的意义，牛津小组在建立将用于这种搜索的技术方面发挥了重要作用。此外，其他物理学目标包括研究低能太阳中微子，反应堆反中微子振荡，寻找核子衰变的非标准模式，研究地球内部产生的地球中微子，以及作为银河系超新星中微子的重要探测器。即将到来的学生将与牛津SNO+小组密切合作，该小组目前由3名学者，1名博士后研究员和4名其他博士生组成，是英国更大努力的一部分，其中包括4个额外的机构：苏塞克斯大学，利物浦大学，KCL和兰开斯特大学。英国SNO+合作者占合作的约30%，并填补了学生也将做出贡献的项目中的许多关键职位。牛津大学小组的负责人史蒂夫·比勒是英国的发言人，并领导了闪烁体中碲装载技术的开发工作，用于无中微子双β衰变，牛津大学在这方面做出了重大贡献，论文项目将涉及这项工作的扩展。英国小组共同负责为实验提供一个主要的校准系统，其中牛津部分侧重于检测器内的光学散射的原位测量，学生的工作也将涉及与该系统相关的分析。本论文的主要物理工作将集中在产生无中微子双β衰变的主要结果。探测器目前正在从水过渡到闪烁体填充，未来两年将引入无中微子双β衰变的同位素。即将到来的博士生将参与开发，模拟，校准，操作，分析和一些中心实验结果的产生。

Some of the most exciting physics to emerge over the last decade has been in the field of neutrino physics. One of the forefront experiments here has been the Sudbury Neutrino Observatory (SNO), based in the SNOLAB underground scientific laboratory in Sudbury, Ontario (Canada), which was a recipient of the 2015 Nobel Prize in physics. The SNO group at Oxford have played a leading role in solving the "Solar Neutrino Problem" and clearly demonstrating, for the first time, that neutrinos exists as mixed states which allow them to apparently "oscillate" from one type to another. On the heels of this tremendously successful project, a follow-on experiment, SNO+, is being pursued with a remarkably diverse and interesting range of physics objectives. The main objective of this project is to sensitively search for a very rare process called "neutrinoless double beta decay." An observation of this would both permit a determination of the absolute neutrino masses and would establish that neutrinos act as their own antiparticles, which could have significant consequences for our understanding of the matter/antimatter asymmetry in the universe. This area of study is considered to be of extremely high importance in particle physics and the Oxford group has played a fundamental role in establishing the technique that will be used for this search. In addition, other physics goals include studies of low energy solar neutrinos, oscillations of reactor antineutrinos, searches for non-standard modes of nucleon decay, study of geo-neutrinos generated from within the earth, and to act as an important detector for neutrinos from galactic supernovae. The incoming student will work closely with the Oxford SNO+ group, which currently consists of 3 academics, 1 postdoctoral researcher and 4 other PhD students and is part of a larger UK effort, which includes 4 additional institutions: University of Sussex, University of Liverpool, KCL and University of Lancaster. The UK SNO+ collaborators comprise ~30% of the collaboration and fill many key positions within the project to which the student will also contribute. The head of the Oxford group, Steve Biller, is the UK spokesperson and leads the development effort on tellurium loading techniques in scintillator for neutrinoless double beta decay, where Oxford has made significant contributions and the thesis project will involve an extension of this work. The UK groups jointly have responsibility for delivering one of the major calibration systems for the experiment, the Oxford portion of which focuses on in situ measurements of optical scattering within the detector, and the student's work will also involve analysis related to this system. The main physics effort for the thesis will focus on producing the main results on neutrinoless double beta decay. The detector is currently undergoing the transition from water to scintillator fill and the isotope for neutrinoless double beta decay will be introduced over the next two years. The incoming PhD student will participate in development, simulation, calibration, operation, analysis and the production of some of the central experimental results.