Impact of unitarity violation on sensitivity of the leptonic CP phase at Hyper-Kamiokande and DUNE

TL;DR

This study evaluates how unitarity violation affects the ability of Hyper-Kamiokande and DUNE to measure the leptonic CP phase, showing Hyper-Kamiokande's robustness and DUNE's sensitivity dependence on non-unitarity scenarios.

Contribution

It provides a detailed simulation of non-unitarity effects on future neutrino experiments' sensitivity to CP violation and explores how to improve their constraints on non-unitarity parameters.

Findings

Hyper-Kamiokande maintains >5σ sensitivity despite non-unitarity.

DUNE's sensitivity drops below 5σ in some non-unitarity scenarios.

Properly accounting for non-unitarity can enhance experimental constraints.

Abstract

We study the impact of unitarity violation on the sensitivity of the leptonic CP phase, $\delta_{CP}$, considering the next generation of long-baseline neutrino experiments, Hyper-Kamiokande and DUNE. By simulating near and far detectors and assuming different scenarios for non-unitarity, we verify how it can affect the sensitivity to measure the $\delta_{ CP}$ violating phase. We also probe the capability of these experiments to constrain the non-unitarity parameters and how their capability could be improved if the impact of non-unitarity at both near and the far detectors were properly taken into account. We find that the Hyper-Kamiokande experiment is robust in the presence of non-unitarity mixing, achieving a sensitivity above $5\sigma$ for our all considered cases. On the other hand, DUNE suffers somewhat more impact due to unitarity violation, reaching a sensitivity below 5$\sigma$ for some values of $\delta_{CP}$. However, depending on the scenario adopted for non-unitarity, DUNE demonstrates robustness in the sensitivity to $\delta_{ CP}$ phase.