Neutrino Mass Ordering -- Circumventing the Challenges using Synergy between T2HK and JUNO

TL;DR

This paper demonstrates that combining data from the JUNO and T2HK neutrino experiments significantly improves the measurement of neutrino mass ordering, achieving over 9σ significance across all parameters and relaxing experimental constraints.

Contribution

The study shows that the synergy between JUNO and T2HK enhances neutrino mass ordering determination, surpassing individual capabilities and reducing experimental requirements.

Findings

Combined analysis yields >9σ significance for MO across all δ_CP values.

Synergy allows JUNO to perform well with 5% energy resolution.

MO sensitivity exceeds 6σ with combined data and 5% JUNO resolution.

Abstract

One of the major open problems of neutrino physics is MO (mass ordering). We discuss the prospects of measuring MO with two under-construction experiments T2HK and JUNO. JUNO alone is expected to measure MO with greater than $3\sigma$ significance as long as certain experimental challenges are met. In particular, JUNO needs better than 3$\%$ energy resolution for MO measurement. On the other hand, T2HK has rather poor prospects at measuring the MO, especially for certain ranges of the CP violating parameter $\delta_{\rm CP}$, posing a major drawback for T2HK. In this letter we show that the synergy between JUNO and T2HK will bring two-fold advantage. Firstly, the synergy between the two experiments helps us determine the MO at a very high significance. With the baseline set-up of the two experiments, we have a greater than $9\sigma$ determination of the MO for all values of $\delta_{\rm CP}$. Secondly, the synergy also allows us to relax the constraints on the two experiments. We show that JUNO, could perform extremely well even for energy resolution of 5$\%$, while for T2HK the MO problem with "bad" values of $\delta_{\rm CP}$ goes away. The MO sensitivity for the combined analysis is expected to be greater than $6\sigma$ for all values of $\delta_{\rm CP}$ and with just 5$\%$ energy resolution for JUNO.