Neutrino mass limit from tritium beta decay

TL;DR

This paper reviews recent tritium beta decay experiments that set an upper limit on the electron neutrino mass at 2 eV, discusses systematic effects, and outlines future experiments aiming for even greater sensitivity.

Contribution

It provides a comprehensive review of experimental techniques, results, and systematic considerations in neutrino mass measurements via tritium beta decay, and discusses future experimental prospects.

Findings

Upper limit on neutrino mass: < 2 eV at 95% C.L.

Systematic effects significantly impact mass measurements.

Next-generation experiments aim for 0.2 eV sensitivity.

Abstract

The paper reviews recent experiments on tritium beta spectroscopy searching for the absolute value of the electron neutrino mass $m(\nu_e)$. By use of dedicated electrostatic filters with high acceptance and resolution, the uncertainty on the observable $m^2(\nu_e)$ has been pushed down to about 3 eV$^2$. The new upper limit of the mass is $m(\nu_e) < 2$ eV at 95% C.L. In view of erroneous and unphysical mass results obtained by some earlier experiments in beta decay, particular attention is paid to systematic effects. The mass limit is discussed in the context of current neutrino research in particle- and astrophysics. A preview is given of the next generation of beta spectroscopy experiments currently under development and construction; they aim at lowering the $m^2(\nu_e)$-uncertainty by another factor of 100, reaching a sensitivity limit $m(\nu_e) < 0.2$ eV.