Joint Analysis Between Atmospheric and Accelerator Neutrinos

Abstract

The results from the first joint oscillation analysis of atmospheric neutrinos at Super-Kamiokande and accelerator neutrinos at Tokai-to-Kamioka are presented in this thesis. By leveraging the unique sensitivities of Super-Kamiokande atmospheric neutrinos to mass ordering and Tokai-to-Kamioka accelerator neutrinos to the CP violation phase, this joint analysis enhances sensitivity through the resolution of parameter degeneracies. A common model was developed for the joint analysis, and an approach utilizing the fitting software framework used for Super-Kamiokande analysis, was further developed specifically for this analysis. The results show a weak preference for the normal mass ordering, with a CLs of accepting the inverted mass ordering at around 0.183. The CP-conserving value of the Jarlskog invariant is excluded with a significance varying between 1.9σ and 2.0σ depending on the analysis considered. Additionally, the marginalized likelihood using the Markov chain Monte Carlo method is developed in the Super-Kamiokande software and will further benefit oscillation analysis in the future. The potential for future joint fits is also studied using the expected sensitivities on oscillation parameters. Furthermore, Hyper-Kamiokande is shown to have the potential to exclude CP-conservation at the 5σ level by combining atmospheric and accelerator neutrinos with unknown mass ordering within 10 years of operation.

Date of Award	1 Dec 2024
Original language	English
Awarding Institution	King's College London
Supervisor	Francesca Di Lodovico (Supervisor)