Measuring the Sterile Neutrino CP Phase at DUNE and T2HK

TL;DR

This paper investigates how well future long-baseline experiments DUNE and T2HK can measure the sterile neutrino CP phase δ24, despite these phases not being accessible in dedicated short-baseline experiments.

Contribution

It demonstrates for the first time the potential of DUNE and T2HK to measure sterile neutrino CP phases and their combination improves measurement precision.

Findings

DUNE and T2HK can measure the sterile CP phase δ24.

Combining DUNE with T2HK/T2HKK enhances measurement accuracy.

Sensitivity to sterile mixing angles improves with combined data.

Abstract

The CP phases associated with the sterile neutrino cannot be measured in the dedicated short-baseline experiments being built to test the sterile neutrino hypothesis. On the other hand, these phases can be measured in long-baseline experiments, even though the main goal of these experiments is not to test or measure sterile neutrino parameters. In particular, the sterile neutrino phase $\delta_{24}$ affects the charged-current electron appearance data in long-baseline experiment. In this paper we show for the first time how well the sterile neutrino phase $\delta_{24}$ can be measured by the next-generation long-baseline experiments DUNE, T2HK (and T2HKK). We also show the expected precision with which this sterile phase can be measured by combining the DUNE data with data from T2HK or T2HKK. We also present the sensitivity of these experiments to the sterile mixing angles, both by themselves, as well as when DUNE is combined with T2HK or T2HKK.