Leptonic CP violation: understanding the matter-antimatter asymmetry in the universe

我们目前对物理学的理解无法解释为什么我们周围的宇宙绝大多数是由物质而不是反物质组成的。我在T2K实验上的工作是研究一种名为中微子的粒子在长途旅行时的振荡，它已经看到了一种新类型的物质-反物质差异的迹象，这种差异有可能为物质主导的宇宙提供解释。更大的数据集和更小的不确定性是确认这些差异所必需的。我的奖学金将解决这两个问题。在奖学金期间，目前正在进行的长距离中微子振荡实验T2K和NOVA将收集到迄今为止最大的中微子振荡数据集。我将领导对T2K数据的分析，这将是第一次足够敏感，为中微子中物质与反物质的差异提供非常重要的证据。除了使用更大的数据集，我还将在分析中添加新的中微子事件样本，将可以研究的中微子相互作用的数量增加约30%。这些新样本不仅将进一步增加可用数据的大小，还将使我们更好地了解中微子与我们的探测器如何相互作用，使我们能够减少由于我们对中微子相互作用的了解而在分析中的不确定性。由此产生的分析将是对任何单个实验中中微子物质-反物质差异的最精确限制。目前，T2K和NOVA分别分析他们的数据。这种分离意味着，每个实验所拥有的能够改善另一个实验分析的信息被忽略了。在这次团契期间，我将与Nova实验的合作者一起首次一起分析T2K和Nova数据。这一结果将对中微子部门的物质-反物质差异产生比这两个实验单独产生的更精确的约束，最大限度地发挥这些英国政府资助的实验的影响。这项耗资10亿美元的规模沙丘实验计划在2020年代中期开始获取数据，预计将比T2K和Nova的中微子振荡数据集更大。然而，我们目前对中微子与探测器材料相互作用的了解还不够好，不足以利用这些数据集。我将为沙丘开发一个高压气体时间投影室(HPgTPC)的一部分，它将测量以前探测器无法访问的中微子相互作用类型。由此产生的中微子-物质相互作用不确定性的减少将使沙丘有能力确切地观察和全面描述中微子物质-反物质不对称。从长远来看，这种类型的探测器在更好地了解辐射是如何沉积在材料中的方面有潜在的医疗应用，例如那些用于放射治疗的材料。这项奖学金将使我能够领导HPgTPC的数据采集(DAQ)电子设备的建设。DAQ电子学允许HPgTPC记录感兴趣的中微子相互作用。要做到这一点，我将使用高速现场可编程门阵列电子设备，这些电子设备在STFC的科学领域具有广泛的适用性，更广泛地包括医疗领域、金融科技和国家安全。此外，英国公司将能够制造该系统的部件，从而促进英国的高科技行业。我还将领导一个项目，在低能粒子束中进行HPgTPC的原型测试。这些测试将使探测器得到准确校准，并提高我们对这些低能粒子与各种不同材料相互作用的了解。沙丘的分析不确定度从3%减少到2%，将相应地减少33%的运行时间，以实现对中微子部门物质-反物质不对称的明确观测，使我们能够用同样的资金做更多的物理工作。

Our current understanding of physics does not explain why the universe around us is made overwhelmingly of matter and not antimatter. My work on the T2K experiment, which studies the oscillations of a type of particle called the neutrino as it travels long distances, has seen hints of a new type of matter-antimatter difference which has the potential to provide an explanation for the matter dominated universe. Larger datasets and smaller uncertainties are necessary to confirm these differences. My fellowship will address both of these issues.During the fellowship, the currently running long distance neutrino oscillation experiments, T2K and NOvA, will collect their largest neutrino-oscillation datasets to date. I will lead the analysis of T2K's data, which will, for the first time, be sensitive enough to provide highly significant evidence for matter-antimatter differences in neutrinos. As well as using the larger dataset, I will add new samples of neutrino events to the analysis, increasing the number of neutrino interactions that can be studied by approximately 30%. Not only will these new samples further increase the size of the available data, they will also give us a better understanding of how neutrinos interact with our detectors, allowing us to reduce the uncertainties in our analyses due to our knowledge of neutrino interactions. The resulting analysis will be the most precise constraint on matter-antimatter differences in neutrinos from any single experiment.Currently T2K and NOvA analyse their data separately. This separation means that information that each experiment has that would improve the other's analysis is ignored. During this fellowship I would work with collaborators in the NOvA experiment to analyse T2K and NOvA data together for the first time. The result will be a more precise constraint on matter-antimatter differences in the neutrino sector than either experiment could produce alone, maximising the impact of these UK government funded experiments.The billion-dollar scale DUNE experiment, which is scheduled to start taking data in the mid 2020s, promises even larger neutrino oscillation datasets than those from T2K and NOvA. However, our current understanding of neutrino interactions with our detector materials is not good enough to take advantage of these datasets. I will develop part of a High-Pressure gas Time Projection Chamber (HPgTPC) for DUNE that will measure neutrino interactions of a type inaccessible to previous detectors. The resulting reduction in our uncertainties on neutrino-matter interactions will give DUNE the capability to definitively observe and fully characterise the neutrino matter-antimatter asymmetry. In the long term there are potential medical applications of this type of detector in better understanding how radiation is deposited in materials, such as those used in radiotherapy.The subsystem that this fellowship will allow me to lead the construction of is the HPgTPC's data acquisition (DAQ) electronics. DAQ electronics allow the HPgTPC to record the neutrino interactions of interest. To do this, I will use high-speed FPGA electronics which have wide applicability both within STFC's science area and more widely including the medical sector, fintech and national security. Furthermore, UK companies will be able to manufacture parts of the system, furthering the UK's high-tech sector. I will also lead a program of prototype tests of the HPgTPC in beams of low energy particles. These tests will allow the detector to be accurately calibrated and improve our knowledge of the interaction of these low energy particles with a variety of different materials. A reduction of DUNE's analysis uncertainties from 3% to 2% will correspond to a 33% reduction in the running time necessary to achieve definitive observation of matter-antimatter asymmetry in the neutrino sector, allowing us to do more physics with the same amount of funding.