Comment on "Strong Evidence for the Normal Neutrino Hierarchy"

TL;DR

This paper critiques a recent claim of strong evidence for the normal neutrino mass hierarchy, arguing that the conclusion is heavily influenced by prior assumptions rather than data.

Contribution

It highlights how prior choices in Bayesian analysis can significantly bias conclusions about neutrino mass ordering.

Findings

The Bayesian odds favoring normal hierarchy are largely due to prior assumptions.

Data alone does not strongly support the normal hierarchy over the inverted.

Prior choices can dominate Bayesian inference outcomes in neutrino mass studies.

Abstract

In the preprint arxiv:1703.03425 "strong evidence" for the normal neutrino mass ordering is claimed. The authors obtain Bayesian odds of 42:1 in favour of the normal ordering. Their conclusion is based on adopting a flat logarithmic prior for the three neutrino masses. Such an assumption favours a hierarchical spectrum for the masses, which is much easier to accommodate for the normal mass ordering, and hence their prior assumption makes the inverted ordering much less likely a priori. We argue that the claimed "evidence" for normal ordering is almost entirely driven by the adopted prior and not due to the data itself.