Neutrino Mass Hierarchy

TL;DR

This paper reviews the current status and future prospects of determining the neutrino mass hierarchy, a key unresolved question in neutrino physics with implications for understanding neutrino nature and flavor theory.

Contribution

It provides a comprehensive summary of experimental and theoretical efforts and discusses future opportunities in light of recent discoveries like the non-zero $ heta_{13}$ angle.

Findings

Summary of experimental progress in neutrino mass hierarchy determination

Analysis of theoretical models related to neutrino mass ordering

Discussion of future experimental prospects and challenges

Abstract

The neutrino mass hierarchy, i.e., whether the $\nu_3$ neutrino mass eigenstate is heavier or lighter than the $\nu_1$ and $\nu_2$ mass eigenstates, is one of the remaining undetermined fundamental features of the neutrino Standard Model. Its determination would represent an important step in the formulation of the generalized model, and would have a profound impact on the quest of the nature of neutrinos (Dirac or Majorana) and the search for a theory of flavor. In this review, we summarize the status of experimental and theoretical work in this field and explore the future opportunities that emerge in light of the recently discovered non-zero and relatively large third neutrino mixing angle $\theta_{13}$.