JUNO's prospects for determining the neutrino mass ordering

TL;DR

JUNO aims to determine the neutrino mass ordering by 2030, with a probability of 31% based on current knowledge, and improved measurements could significantly enhance this likelihood.

Contribution

This paper assesses JUNO's potential to determine neutrino mass ordering by 2030 using current data and explores how future measurements and global fits can improve this.

Findings

JUNO has a 31% chance to determine the mass ordering by 2030 without additional data.

Improved measurements of oscillation parameters will increase JUNO's standalone determination probability.

Global fits combining JUNO data with other experiments can lead to earlier mass ordering determination.

Abstract

The flagship measurement of the JUNO experiment is the determination of the neutrino mass ordering. Here we revisit its prospects to make this determination by 2030, using the current global knowledge of the relevant neutrino parameters as well as current information on the reactor configuration and the critical parameters of the JUNO detector. We pay particular attention to the non-linear detector energy response. Using the measurement of $\theta_{13}$ from Daya Bay, but without information from other experiments, we estimate the probability of JUNO determining the neutrino mass ordering at $\ge$ 3$\sigma$ to be 31% by 2030. As this probability is particularly sensitive to the true values of the oscillation parameters, especially $\Delta m^2_{21}$, JUNO's improved measurements of $\sin^2 \theta_{12}$, $\Delta m^2_{21}$ and $|\Delta m^2_{ee}|$, obtained after a couple of years of operation, will allow an updated estimate of the probability that JUNO alone can determine the neutrino mass ordering by the end of the decade. Combining JUNO's measurement of $|\Delta m^2_{ee}|$ with other experiments in a global fit will most likely lead to an earlier determination of the mass ordering.