Strengthening the bound on the mass of the lightest neutrino with terrestrial and cosmological experiments

TL;DR

This paper establishes the most stringent upper limits to date on the lightest neutrino mass using combined cosmological and terrestrial data, considering different mass orderings and early universe conditions.

Contribution

It provides improved bounds on the lightest neutrino mass by integrating recent data and analyzing effects of various cosmological parameters and mass models.

Findings

Lightest neutrino mass < 0.037 eV (normal ordering)

Lightest neutrino mass < 0.042 eV (inverted ordering)

Results are more robust and tighter than previous limits

Abstract

We determine the upper limit on the mass of the lightest neutrino from the most robust recent cosmological and terrestrial data. Marginalizing over possible effective relativistic degrees of freedom at early times ($N_\mathrm{eff}$) and assuming normal mass ordering, the mass of the lightest neutrino is less than 0.037 eV at 95% confidence; with inverted ordering, the bound is 0.042 eV. These results improve upon the strength and robustness of other recent limits and constrain the mass of the lightest neutrino to be barely larger than the largest mass splitting. We show the impacts of realistic mass models, and different sources of $N_\mathrm{eff}$.