New upper limit on neutrino mass from the KATRIN experiment*

Neutrinos are proved to be massive from their flavor oscillations. Despite the fact that neutrino mass splittings have been measured with high precision, the absolute neutrino mass scale remains unknown. Recent cosmological observations and neutrinoless double beta decay experiments have set model-dependent upper limits for the absolute neutrino mass. A direct, model-independent measurement of the neutrino mass scale therefore provides a key input for cosmological models and particle physics.

The Karlsruhe Tritium Neutrino (KATRIN) experiment plays a leading role in direct neutrino mass measurements, by combining a high activity gaseous tritium source with a state-of-the-art spectrometer of MAC-E-filter type. An overall background reduction of 50% and significant improvements in the systematic uncertainties have been reached since KATRIN’s last data release. With 259 days of measurement time and about 36 million electrons collected in the region of interest from KATRIN’s first five measurement campaigns, an improved upper limit of m_ν < 0.45 eV has been obtained at 90% confidence level. KATRIN is on track to achieve five times the current data release statistics and a final sensitivity of better than m_ν < 0.3 eV by the end of 2025.