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Physics: Smallest neutrino mass recorded

Nature Physics

February 15, 2022

The mass of the electron antineutrino — a type of elementary particle — has been determined as below one electronvolt or 1.6 × 10^–36 kg, according to a paper published in Nature Physics.

Neutrinos are weakly interacting, uncharged particles that come in three different types: the electron, muon and tau neutrinos. Compared to those of most other elementary particles, neutrino masses are tiny. Although neutrino oscillations have shown that neutrinos have mass, their actual masses are unknown.

The KATRIN collaboration studied tritium, a radioactive isotope that decays into helium, an electron and an electron antineutrino — the antiparticle of an electron neutrino. Depending on the mass of the neutrino, the maximal energy distribution of the decay can differ. By increasing the number of tritium decays —while reducing contaminations from other types of radioactive decay — the team were able to reveal the effective mass of the electron antineutrino to be less than 0.8 electronvolt or 1.6 × 10^–36 kg.

Combining this result with measurements from KATRIN’s first campaign has allowed the mass of neutrinos to be refined, advancing our understanding of neutrinos little by little.

doi: 10.1038/s41567-021-01463-1

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