Using neutrinos to unravel the mysteries of the universe

中微子是我们所知的最鲜为人知的粒子。它们的质量极小，很少相互作用，但它们极其丰富，对我们宇宙的演化至关重要。中微子有三种类型(电子中微子、Muon中微子和tau中微子)，自20世纪90年代以来，我们已经知道中微子可以在旅行中改变其味道。关于中微子，还有两个大问题需要解决。首先，令人惊讶的是，我们还不知道哪一个是最轻的中微子。发现第三个中微子比另外两个中微子重，这将为许多大统一理论提供证据，这些理论试图将粒子相互作用解释为单一力量的不同表现。如果不是这样，我们对宇宙中自然力的看法将完全改变。第二个问题是，中微子和反中微子的振荡方式是否相同。回答这个问题可能会解开关于宇宙起源的最大谜团之一：大爆炸应该创造出等量的物质和反物质，但今天，我们周围的一切，从最小的微生物到最大的恒星物体，几乎完全由物质构成。如果中微子和反中微子的振荡遵循不同的规则，这可能是为什么宇宙进化成由物质而不是反物质主导的原因，从而允许恒星、行星甚至我们的存在。这一奖项将允许我使用连贯的策略来解决这两个谜团，遵循两个最有能力回答它们的雄心勃勃的实验计划：新星和沙丘。NOVA是世界领先的长基线中微子实验：芝加哥附近的费米国家加速器实验室(FNAL)产生了一束强烈的Muon中微子，并将其定向到800公里外的明尼苏达州。Nova使用近距离和远距离探测器来测量fNAL产生的中微子的味道，以及到达明尼苏达州的中微子的味道。沙丘是未来世界中微子振荡测量的旗舰实验，由美国能源部批准，全额资助，目前处于建设阶段。沙丘将使用来自FNAL的强烈的Muon中微子光束，并将其引导到1300公里外的南达科他州。沙丘将使用比NOVA更强大的光束、更大的远探测器和更好的探测器技术。由于中微子只有在与探测器中的物质相互作用并产生其他粒子时才能被探测到，目前的理论中微子相互作用模型是中微子振荡分析中最大系统不确定性的原因。(反)中微子相互作用及其产物的高精度截面测量是精确测量中微子振荡参数的关键。我的策略是使用新星近距离探测器积累的高统计数据和沙丘近距离探测器的原型来执行这样的测量。这些结果将直接影响新星和沙丘中微子振荡分析。此外，我将领导Nova-T2K联合中微子振荡分析。这一分析的主要挑战在于两个实验使用的中微子相互作用模型截然不同。我在T2K期间对中微子截面和振荡分析做出了重大贡献，目前领导新星束模拟和数据组，以及新星近探测器截面组，因此我唯一有资格领导和确保这次联合分析的成功。这将是下一代实验启动前最重要的中微子物理测量。我在布里斯托尔的团队在新星期间获得的经验和声誉也将确保我们在沙丘振荡分析方面的领先地位。这一奖学金将使我能够建立并领导布里斯托尔大学的中微子小组，走在中微子物理学两项非凡发现的前沿。

Neutrinos are the least understood particles we know of. They have extremely small mass and they rarely interact, yet they are extremely abundant and are critical for the evolution of our universe. Neutrinos come in three flavours (electron, muon and tau neutrinos), and since the 1990s we have known that a neutrino can change its flavour as it travels. There are still two big questions left to address about neutrinos. The first is that, surprisingly, we do not yet know which is the lightest neutrino. Finding that the third neutrino is heavier than the other two would give evidence for many Grand Unified Theories that seek to explain particle interactions as different manifestations of a single force. If that is not the case, the way we think about the natural forces in the universe will be completely changed. The second question is whether neutrinos and antineutrinos oscillate in the same way. Answering this question might solve one of the biggest mysteries about the origin of the universe: the Big Bang should have created equal amounts of matter and antimatter, but today, everything around us, from the smallest microorganism to the largest stellar object, is made almost entirely by matter. If neutrinos and antineutrinos oscillate following different rules, they might be the reason why the universe evolved to be dominated by matter rather than antimatter, hence allowing the existence of stars, planets and even us.This award will allow me to use a coherent strategy to solve these two mysteries, following the ambitious programme of the two experiments best equipped to answer them: NOvA and DUNE. NOvA is a world leading long baseline neutrino experiment: an intense beam of muon neutrinos is produced at the Fermi National Accelerator Laboratory (FNAL), near Chicago, and directed 800 km away towards Minnesota. NOvA uses a near and a far detector to measure the flavour of the neutrinos produced at FNAL, and the flavour of the neutrinos that arrive in Minnesota. DUNE is the future world flagship experiment for neutrino oscillation measurements, fully funded, approved by the US Department of Energy, and currently in the construction phase. DUNE will use the intense muon neutrino beam from FNAL and direct it 1300 km away towards South Dakota. DUNE will use a more powerful beam, a much bigger far detector, and better detector technology than NOvA.As neutrinos can only be detected when they interact with the matter in the detector and produce other particles, currently theoretical neutrino interaction models are the cause of the largest systematic uncertainties in neutrino oscillation analyses. High precision cross-section measurements of (anti)neutrino interactions and their products are essential for the precision measurements of neutrino oscillation parameters. My strategy is to perform such measurements using the high statistics accumulated by the NOvA near detector, and a prototype of the DUNE near detector. These results will directly impact both the NOvA and DUNE neutrino oscillation analyses. Additionally, I will lead the NOvA-T2K joint neutrino oscillation analysis. The main challenge of this analysis is presented by the very different neutrino interaction models that the two experiments use. Having made major contributions to neutrino cross section and oscillation analyses during my time on T2K, and currently leading the NOvA Beam simulation and data group, and also the NOvA near detector cross section group, I am uniquely qualified to lead and ensure the success of this joint analysis. This will be the most important neutrino physics measurement before the next generation experiments turn on. The experience and reputation gained during the NOvA years by my group at Bristol will ensure our leadership in the DUNE oscillation analysis too.This fellowship will allow me to establish and lead the neutrino group at the University of Bristol to be at the forefront of two extraordinary discoveries in neutrino physics.