Combined sensitivity to the neutrino mass ordering with JUNO, the IceCube Upgrade, and PINGU

TL;DR

This paper evaluates how combining JUNO, IceCube Upgrade, and PINGU experiments can conclusively determine the neutrino mass ordering within a few years, leveraging their complementary detection methods.

Contribution

It demonstrates that joint analysis of these experiments can achieve >5σ confidence in neutrino mass ordering within 3-7 years, even under challenging conditions.

Findings

JUNO and IceCube Upgrade can exclude the wrong mass ordering at >5σ in 3-7 years.

PINGS can exclude the inverted ordering within 1.5 years in joint analysis.

Combined approaches outperform individual sensitivities for neutrino mass ordering determination.

Abstract

The ordering of the neutrino mass eigenstates is one of the fundamental open questions in neutrino physics. While current-generation neutrino oscillation experiments are able to produce moderate indications on this ordering, upcoming experiments of the next generation aim to provide conclusive evidence. In this paper we study the combined performance of the two future multi-purpose neutrino oscillation experiments JUNO and the IceCube Upgrade, which employ two very distinct and complementary routes towards the neutrino mass ordering. The approach pursued by the $20\,\mathrm{kt}$ medium-baseline reactor neutrino experiment JUNO consists of a careful investigation of the energy spectrum of oscillated $\bar{\nu}_e$ produced by ten nuclear reactor cores. The IceCube Upgrade, on the other hand, which consists of seven additional densely instrumented strings deployed in the center of IceCube DeepCore, will observe large numbers of atmospheric neutrinos that have undergone oscillations affected by Earth matter. In a joint fit with both approaches, tension occurs between their preferred mass-squared differences $ \Delta m_{31}^{2}=m_{3}^{2}-m_{1}^{2} $ within the wrong mass ordering. In the case of JUNO and the IceCube Upgrade, this allows to exclude the wrong ordering at $>5\sigma$ on a timescale of 3--7 years --- even under circumstances that are unfavorable to the experiments' individual sensitivities. For PINGU, a 26-string detector array designed as a potential low-energy extension to IceCube, the inverted ordering could be excluded within 1.5 years (3 years for the normal ordering) in a joint analysis.