How heavy are neutrinos?

What is the mass of the lightest known elementary particles? Neutrinos still pose numerous mysteries to us such as this one more than 90 years after their postulation. The reason is because determining their mass, which is still unknown today, is extremely technologically demanding. The discovery of neutrino oscillations proves that neutrinos have a mass, but does not allow determination of this important quantity.

At the Karlsruhe Institute of Technology (KIT), KATRIN is able to place neutrinos on the world's most sensitive scale for elementary particles with unprecedented accuracy by measuring the missing energy of electrons released along with neutrinos in the nuclear transformation of tritium. Since the start of the multi-year measurements in 2019, the neutrino mass has already been significantly narrowed down. Central to this is a huge, high-resolution spectrometer and an ultra-stable, cryogenic tritium source.

Involving 20 institutions from seven countries, the KATRIN collaboration is not only a highly visible beacon for basic research and unique high-tech instrument but also an excellent example of cooperation and first-class training for young scientists.

(Header: M. Zacher/KATRIN Collaboration)