KATRIN: the upper limit of the neutrino mass is below 0.8 eV

The international research team of the KATRIN project with Czech participation announced in the leading scientific journal Nature Physics that its new measurements reduced the upper limit of the mass of the neutrino, the lightest elementary particle of matter, to 0.8 electron volts (eV, 1 eV = 1.8x10^-36 kg).

Determining the rest mass of neutrinos is an important goal in particle physics as well as in astrophysics and cosmology. We have already known – according to independent experiments awarded the Nobel Prize in Physics in 2015 – that mass is non-zero: at least in one of the three states in which neutrinos occur, it is at least 0.05 eV.

By combining data from two series of measurements, the team determined with 90 % statistical reliability the upper limit of the neutrino mass m < 0.8 eV. After many years of efforts by experimental physicists, the symbolic limit of 1 eV was overcome for the first time.

The new results were achieved mainly due to an increase in the intensity of the cryogenic source of gaseous tritium to four times the previous value and a quarter decrease in the signal of the interfering environment. The contribution of participants from NPI of the CAS is summarized by Dr. Drahoslav Vénos: “Thanks to our experience in nuclear spectroscopy, radiochemistry and accelerator technology, we have succeeded in developing sources of calibration of monoenergetic electrons that meet all the extreme requirements of the KATRIN experiment. These sources are necessary for the proper operation of the entire facility. "

The entire common Czech Academy of Sciences and NPI of the CAS press release in Czech on this event, based on the press release of the KATRIN collaboration, can be found here, CAS news in Czech can be found here.