Neutrino oscillations and the search for CP violation in T2K

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.