Neutrino oscillation at T2K and Hyper Kamiokande and development of the Hyper Kamiokande light injection calibration system

Neutrino oscillations are crucial phenomena in the Standard model of particle physics or specifically the physics beyond the Standard model, yet many questions remain unanswered. The CP-violating phase remains elusive, and the exact nature of neutrino mass hierarchy is still unknown. Thus, the Hyper Kamiokande (Hyper-K) experiment, a leading endeavour in neutrino physics, is poised to unlock the mysteries of neutrino oscillations and CP violation. This research stems from the ever-increasing need for precision and innovation in neutrino science and so Hyper-K aims to expand our understanding of these phenomena by leveraging advancements in experimental techniques and offers a unique opportunity to delve into neutrino oscillation studies. This ambitious project builds upon the success of the T2K experiment and will be pivotal in shaping the future of neutrino physics. This project enhances our understanding of neutrino oscillations, specifically focusing on the search for CP violation using the T2K experiment and Hyper-K data. While T2K has made remarkable progress, more data, an upgraded ND280 detector, and increased beam power are required to achieve ultimate sensitivity. The primary aim is to develop and construct elements of the Hyper-K light injection calibration system and analyse its data. By doing so, we intend to fill the gaps in our knowledge and pave the way for the next phase of this research. The research project presents a two-fold approach to reduce systematics in the Hyper-K detector systematics and the oscillation fit for the T2K experiment. The overarching goal is to improve the precision and accuracy of the experiments by minimising uncertainties stemming from both the detector systematics and the data analysis. The first part is aimed to enhance the performance of the Hyper-K detector by optimising the light injection system and using it to determine detcor properties with associated uncertainties. Alongside this hardware work, the Water Cherenkov Simulation (WCSim) will be employed to model the detector response to neutrino interactions. The simulated events will be used to study the impact of measured detector properties on the measured signals. The second part of this research aims to incorporate the improved detector systematics into the oscillation fit for the T2K and Hyper K experiments. Therefore, the T2K oscillation fit will be upgraded with the updated detector systematics to improve the precision of the neutrino oscillation measurements. Extensive simulations and statistical analyses will be conducted to assess the impact of these changes on the fit's performance. By combining these two research efforts, we aim to substantially reduce systematic uncertainties in the Hyper-K detector and improve the precision of neutrino oscillation measurements in the T2K experiment. In conclusion, this project bridges the gap in our knowledge of neutrino oscillations and CP violation. The development and construction of the Hyper-K light injection system, coupled with the analysis of enhanced T2K data, will contribute significantly to the field of particle physics. Understanding CP violation could have profound implications for our understanding of matter-antimatter asymmetry and the evolution of the universe, making this research critically significant in the broader context of science.