PINGU and the neutrino mass hierarchy: Statistical and systematic aspects

TL;DR

The paper analyzes the challenges posed by spectral shape uncertainties in PINGU's efforts to determine the neutrino mass hierarchy, emphasizing the need for refined systematic estimates.

Contribution

It provides a detailed assessment of how spectral shape systematics impact PINGU's sensitivity to the neutrino mass hierarchy and discusses the interplay with mixing angles.

Findings

Shape uncertainties at a few percent level can significantly affect hierarchy sensitivity.

Refined estimates of spectral uncertainties are crucial for future large-volume neutrino experiments.

Interplay between theta_23 and hierarchy sensitivity is a key consideration.

Abstract

The proposed PINGU project (Precision IceCube Next Generation Upgrade) is expected to collect O(10^5) atmospheric muon and electron neutrino in a few years of exposure, and to probe the neutrino mass hierarchy through its imprint on the event spectra in energy and direction. In the presence of nonnegligible and partly unknown shape systematics, the analysis of high-statistics spectral variations will face subtle challenges that are largely unprecedented in neutrino physics. We discuss these issues both on general grounds and in the currently envisaged PINGU configuration, where we find that possible shape uncertainties at the (few) percent level can noticeably affect the sensitivity to the hierarchy. We also discuss the interplay between the mixing angle theta_23 and the PINGU sensitivity to the hierarchy. Our results suggest that more refined estimates of spectral uncertainties are needed in next-generation, large-volume atmospheric neutrino experiments.