Physicists of the Karlsrue Tritium Neutrino (Catlin) experiment have reported so far the most accurate measurement of the upper mass limit of neutrinos, establishing it as 0.45 electron volts (EV), less than a millionth of the electron mass.
Neutrinos are the most abundant particles in the universe and exist as three different types or flavors: Electron Neutrino, Muon Neutrino, and Tau Neutrino.
These flavors vibrate. In other words, a single neutron can be converted to each type when it moves, providing compelling evidence that neutrinos have masses that contradict the original assumptions of massless neutrinos in the standard model.
But their exact mass remains one of the great mysteries of particle physics.
in New paper In the journal Sciencethe physicists from the Catlin collaboration present the results of the first five measurement campaigns of the Catlin experiment.
“The catrin experiment determines the mass of neutrinos by analyzing the beta decay of tritium,” they explained.
“During this decay, the neutrons are converted into protons, releasing both electron and electron antioxidant, the latter being neutrino antiparticles.”
“We can infer the mass of neutrinos by analyzing the distribution of total disintegration energy between the emitted electrons and the electron antioxidants.”
For 259 days between 2019 and 2021, Catlin physicists measured approximately 36 million electrons of energy. This is a dataset of 6 times the previous run.
The findings establish the strictest laboratory base upper limit for effective electron neutrino masses and place them below 0.45 eV at a 90% confidence level.
This result shows a third improvement in the mass limit of neutrinos, and doubles the previous limit.
“For this result, we analyzed five measurement campaigns. The total data collection from 2019 to 2021 is about a quarter of the total data expected from Catlin,” said Dr. Catlin Valerius, one of the two co-spokemens for the Catlin experiment and a physicist at the Karl-Thru Institute.
“In each campaign, we gained new insights and further optimized the experimental conditions,” said Dr. Suzanne Mertens, a physicist at the Max Planck Institute for Nuclear Physics and the Institute of Technology Munich.
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Max Aker et al. (Catlin collaboration). 2025. Direct neutrino mass measurements based on 259 days of catrin data. Science 388 (6743): 180-185; doi: 10.1126/science.adq9592
Source: www.sci.news
