Absolute neutrino mass scale remains unknown

Determine the absolute neutrino mass scale; in particular, ascertain the value of the effective electron antineutrino mass that characterizes the absolute mass of neutrinos beyond the known mass-squared splittings from oscillation experiments.

Background

Neutrino oscillation experiments have precisely measured mass-squared differences but are insensitive to the overall mass scale. As a result, the absolute magnitude of neutrino masses is not fixed by oscillation data alone.

KATRIN addresses this by direct kinematic measurements of the tritium beta-decay spectrum near the endpoint, providing upper limits on the effective electron antineutrino mass. Despite these advances, the absolute mass scale itself is still undetermined.