Signatures of a Light Sterile Neutrino in T2HK

TL;DR

This paper assesses T2HK's ability to detect a light sterile neutrino and its impact on key neutrino physics issues, highlighting the importance of spectral information and energy reconstruction in maintaining sensitivity.

Contribution

It provides a detailed analysis of T2HK's performance in the presence of a light sterile neutrino, emphasizing spectral information's role in preserving sensitivity to mass hierarchy and CP violation.

Findings

Spectral information enhances mass hierarchy discovery in 3ν and 4ν schemes.

Sensitivity to CP violation remains stable when adding a sterile neutrino.

Uncertainty on CP phases is approximately 15° for δ13 and 30° for δ14.

Abstract

We investigate the performance of T2HK in the presence of a light eV scale sterile neutrino. We study in detail its influence in resolving fundamental issues like mass hierarchy, CP-violation (CPV) induced by the standard CP-phase $\delta_{13}$ and new CP-phase $\delta_{14}$, and the octant ambiguity of $\theta_{23}$. We show for the first time in detail that due to the impressive energy reconstruction capabilities of T2HK, the available spectral information plays an important role to enhance the mass hierarchy discovery reach of this experiment in 3$\nu$ framework and also to keep it almost intact even in $4\nu$ scheme. This feature is also of the utmost importance in establishing the CPV due to $\delta_{14}$. As far as the sensitivity to CPV due to $\delta_{13}$ is concerned, it does not change much going from $3\nu$ to 4$\nu$ case. We also examine the reconstruction capability of the two phases $\delta_{13}$ and $\delta_{14}$, and find that the typical 1$\sigma$ uncertainty on $\delta_{13}$ ($\delta_{14}$) in T2HK is $\sim15^0$ ($30^0$). While determining the octant of $\theta_{23}$, we face a complete loss of sensitivity for unfavorable combinations of unknown $\delta_{13}$ and $\delta_{14}$.