Neutrino oscillations and the search for CP violation in T2K

物理学中一个悬而未决的问题是宇宙中物质的起源。为什么宇宙充满了物质而不是反物质？1967年，苏联物理学家安德烈·萨哈罗夫（Andrei Sakharov）假设宇宙的物质-反物质不对称性必须满足三个条件：1）重子数不守恒; 2）电荷宇称（CP）对称性破坏; 3）早期宇宙中的热平衡相互作用。电荷宇称在弱相互作用中被破坏，只在包含夸克的强子的相互作用和衰变中。然而，夸克扇区中的CP破坏水平不足以解释宇宙的物质-反物质不对称性。中微子的CP破坏可能会解决这个问题，通过探索中微子和反中微子在一种味道和另一种味道之间振荡的方式之间的差异。轻子的CP破坏可能导致早期宇宙中的重子不对称，这将为今天在宇宙中观察到的物质-反物质不对称创造条件。在这个项目中，学生将在T2 K实验中使用中微子和反中微子束进行电子-中微子外观测量。这些数据将被用来执行一个近到远探测器的中微子和反中微子振荡的全球拟合，以搜索中微子部门的CP破坏，使用复杂的统计技术。电子-中微子和电子-反中微子之间的差异可能为中微子的CP破坏提供了第一个证据，这将是使用轻子的物质-反物质不对称性的第一个证据。中微子CP破坏的线索已经在T2 K中显示出来。本项目的目的和目标是首次发现中微子CP破坏超过三个标准差的证据，并对导致中微子混合的Pontecorvo-Maki-Nakagawa-Sakata（PMNS）矩阵中CP破坏的复杂相位进行初步测量。在学生期间，学生将发展先进的数据分析和拟合技术，使用在其他科学和商业学科中具有广泛应用的机器学习算法。此外，学生将致力于T2 K仪器的升级，包括新的改进中微子探测器系统的准备工作。一些领域包括为T2 K升级安装的新探测器的开发、测试和调试，或为Hyper-Kamiokande实验测试新的电子板，该实验将是T2 K的后续实验。这些发展对最先进的成像探测器和高速电子设备具有潜在的影响。

One of the outstanding questions in Physics is the origin of matter in the universe. Why is the universe filled with matter and not antimatter? In 1967, the Soviet physicist Andrei Sakharov postulated that three conditions have to be met for the matter-antimatter asymmetry of the universe to arise: 1) non-conservation of baryon number; 2) Charge-Parity (CP) symmetry violation; and 3) interactions out of thermal equilibrium in the early universe. Charge-Parity has been shown to be violated in weak interactions, exclusively in the interactions and decays of hadrons that contain quarks. However, the level of CP violation in the quark sector is not sufficient to explain the matter-antimatter asymmetry of the universe. CP violation of neutrinos could potentially solve this problem, by exploring differences between the way neutrinos and antineutrinos oscillate between one flavour and the other. CP-violation in leptons could give rise to a baryon asymmetry in the early universe, which would create the conditions for the matter-antimatter asymmetry observed in the universe today.In this project, the student will carry out an electron-neutrino appearance measurement in the T2K experiment, using both neutrino and antineutrino beams. These data will be used to perform a near-to-far detector global fit of both neutrino and antineutrino oscillations to search for CP violation in the neutrino sector, using sophisticated statistical techniques. The difference between electron-neutrino and electron-antineutrino appearance could provide the first evidence for CP violation in neutrinos, which would be the first evidence of matter-antimatter asymmetry using leptons. Hints of CP violation in neutrinos have already been shown in T2K. The aims and objectives of this project are to show the first evidence of neutrino CP violation exceeding three standard deviations for the first time and to perform a preliminary measurement of the complex phase responsible for CP violation in the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix that gives rise to neutrino mixing.During the studentship, the student will develop advanced data analysis and fitting techniques, using machine-learning algorithms that have extensive applications in other scientific and commercial disciplines. Furthermore, the student will work on upgrades of the T2K instrumentation, including preparations for new improved neutrino detector systems. Some areas include the development, testing and commissioning of new detectors being installed for the T2K upgrade, or testing new electronic boards for the Hyper-Kamiokande experiment, which will be the successor experiment to T2K. These developments have potential impact in state-of-the-art imaging detectors and high-speed electronics.