Direct probes of neutrino mass

TL;DR

This paper reviews experimental efforts to measure neutrino mass, highlighting the progress and challenges in narrowing down the mass range from laboratory experiments and beta decay measurements.

Contribution

It provides a comprehensive overview of current laboratory techniques and results aimed at directly probing neutrino mass, emphasizing recent advancements and remaining gaps.

Findings

Current upper limit from beta decay is 2 eV.

Oscillation experiments set a lower limit of 0.02 eV.

Progress in laboratory measurements is narrowing the mass window.

Abstract

The discovery of neutrino oscillations has shown that neutrinos, in contradiction to a prediction of the minimal standard model, have mass. Oscillations do not yield a value for the mass, but do set a lower limit of 0.02 eV on the average of the 3 known eigenmasses. Moreover, they make it possible to determine or limit all 3 masses from measurements of electron-flavor neutrinos in beta decay. The present upper limit from such measurements is 2 eV. We review the status of laboratory work toward closing the remaining window between 2 and 0.02 eV, and measuring the mass.