They studied the beta decay of an unstable hydrogen isotope called tritium with a short half-life of 12.3 years, which releases an electron and a neutrino among its decay products. This is exactly how physicists from the KATRIN collaboration put new constraints on the neutrino mass. As a result, their mass is usually measured indirectly by studying the velocity distribution of other particles participating in certain interaction or decay processes. Neutrinos are difficult to study because their interactions with other particles are very weak - a single neutrino moving at nearly the speed of light will need a one hundred light year–thick layer of water to get scattered (and therefore detected). Gaining a more precise measurement of the neutrino mass could therefore help shed light on the origin of particle masses. A neutrino’s mass is at least six orders of magnitude smaller than the mass of any other particle we have discovered, and such a huge gap hints that a different mass creation mechanism may be at play.
In the Standard Model of particle physics, neutrinos are considered massless, but this non-zero mass challenges our current understanding and hints at a concept called “new physics” - physics beyond the Standard Model that could help clarify some of its discrepancies.Īll massive fundamental particles that we know of - from electrons with mass of half of a megaelectron volt (MeV) to 170 GeV t-quarks - obtain their masses through interactions with the Higgs boson. Neutrinos are abundant in the universe and, despite their small size, play an important role in the evolution of large-scale structures in it, such as galaxy formation.Ī direct laboratory measurement of the neutrino mass would have far-reaching implications in both elementary particle physics and cosmology.
Physicists participating in the international Karlsruhe Tritium Neutrino (KATRIN) experiment have just measured the mass of a neutrino with a record-breaking accuracy.Īmong all known subatomic particles with non-zero masses, neutrinos are the lightest with a mass around ten million times less than that of an electron.
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