Direct Measurement of Neutrino Mass

TL;DR

This paper reviews the current constraints on the total neutrino mass from laboratory experiments and cosmological observations, emphasizing the ongoing KATRIN experiment and its significance in direct measurement.

Contribution

It highlights the importance of direct laboratory measurements of neutrino mass, especially through beta decay experiments like KATRIN, and discusses alternative methods using Re-187.

Findings

Neutrino mass sum constrained between 55 and 6900 meV.

Cosmological data favors a mass sum below about 600 meV.

KATRIN experiment aims to measure neutrino mass directly from beta decay.

Abstract

The sum of the masses of the three neutrino mass eigenstates is now constrained both from above and below, and lies between 55 and 6900 meV. The lower limit is set by neutrino oscillations and the fact that masses are non-negative. The upper limit is set by laboratory measurements on the beta decay of tritium. These determinations share a common characteristic of being essentially model independent, or "direct." The clustering on large scales in the universe depends on this quantity, and, within the framework of Lambda-CDM cosmology, favors a mass sum below about 600 meV. In this article, the laboratory approach to neutrino mass via beta decay is emphasized, particularly an experiment now under construction, KATRIN, on the beta decay of tritium. Another candidate beta-active nuclide, Re-187, offers an advantage in phase space but calls for a very different experimental approach.