Neutrinos are fascinating particles – first directly observed in 1954, many of their properties keep surprising us well into the 21st century. They are almost massless, highly unlikely to interact with other matter particles, and when they do, their interactions are notoriously difficult to detect and distinguish from competing background signatures. Neutrinos come in three types, and as they propagate through space their type changes – this fascinating identity-switching metamorphosis was coined neutrino oscillations, and its discovery was awarded the Nobel Prize in Physics in 2015. Many aspects of neutrino oscillations are still being investigated. The Hyper-Kamiokande (Hyper-K) experiment is uniquely positioned to inform with world leading precision on some of these open questions, including whether CP (charge conjugation parity) symmetry, one of the fundamental symmetries in Nature, is violated in the process of neutrino oscillations. CP violation would register as a difference in the oscillation rate of neutrinos compared to that of anti-neutrinos (their anti-matter counterpart). If observed, CP violation would be one of the missing pieces needed to explain how the matter dominated Universe that we live in formed after the Big Bang.

The Particle Physics Department (PPD) at Rutherford Appleton Laboratory and at the University of Liverpool have long standing expertise and involvement with world leading long-baseline neutrino oscillation experiments in Japan, Tokai-to-Kamioka and its successor Hyper-Kamiokande. With the excavation of the underground cavern for Hyper-K completed in July 2025 (at 93 m tall this is now one of the largest man-made spaces ever excavated in bedrock!), the opportunity to join this international experiment is highly timely. Hyper-Kamiokande is scheduled to start data-taking in 2028, and this studentship project will contribute to three key stages as the experiment comes together: installation and detector commissioning in 2027/28 and physics analysis exploitation in 2028/29. 2.7x10^21 protons-on-target worth of data will be collected in the first year of data-taking of Hyper-Kamiokande, paving the way for stringent constraints on the value of the CP phase in the neutrino mixing matrix.

Rutherford Appleton Laboratory and the University of Liverpool made crucial contributions in designing both the data acquisitioning (DAQ) and optical calibration systems for Hyper-Kamiokande and have years of experience in developing high precision neutrino oscillation analyses. The project will involve work on far detector commissioning and data calibration in 2027 and 2028, followed by developing the Hyper-K signal selection in 2028/29 for the first oscillation analysis which will be one of the flagship outputs of the Hyper-K experiment. Many of the DAQ triggers that will be used when the experiment goes live have been developed and validated at RAL, and the Light Injection (LI) system for calibrating the optical response of photo multiplier tubes in the outer and inner detectors of Hyper-K has been developed at Liverpool and is a fully Liverpool-led effort. The interface between the DAQ and LI systems will be crucial in the early stages of the experiment for developing the LI trigger and the LI slow control. With the Liverpool-RAL partnership, the studentship will be exceptionally well supported during the data commissioning, calibration and analyses stages.

The successful candidate will spend the first year of the studentship at the University of Liverpool, where a comprehensive lecture course will be provided in addition to an opportunity to start developing the DAQ and LI system interface in the run up to Hyper-K going live. The second year will be spent on Long Term Attachment (LTA) at the Kamioka Observatory which is part of University of Tokyo’s Institute for Cosmic Ray Research. The student’s LTA is particularly timely and fits in exceptionally well with the planned Hyper-K activities. The student will be excellently supported while on LTA, overlapping largely with periods when the supervisors’ will be based on site as well. The first 3 months, from October 2027, will see the final stages of detector construction, the next 6 months span the tank water-filling stage and crucial tests of the DAQ and calibration systems, and the last 3 months will comprise of data-taking. The successful applicant will have the opportunity to act as a liaison between the DAQ and Calibration groups, which will be reliant on each other to demonstrate successful operation and readiness for data-taking. The project involves the use of the Light Injection system developed at Liverpool to study the water quality in the tank and the light response of the PMTs, which will determine detector systematic inputs for the oscillation analysis. The third year of the studentship will be spent at Rutherford Appleton Laboratory analysing the first beam data and developing signal selection and systematics for the oscillation measurement.