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NEUTRINO PHYSICS

Still too small to be measured

Nature Physics volume 18, pages 128–129 (2022)Cite this article

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Although the mass of the electron antineutrino is still eluding direct measurement, the KATRIN experiment with its huge spectrometer has pushed the sensitivity below a billionth of the proton mass.

Progress in neutrino physics is both time- and resource-consuming. When Wolfgang Pauli first proposed the existence of the neutrino in 1930 to explain the continuous energy spectrum of electrons observed in beta decay, he hypothesized that neutrinos are lighter than electrons or protons, the only other known massive particles at that time, and more penetrating than photons. He was right on every front, but things turned out to be even trickier, so that it took two decades to confirm their existence1. Also, they are so much lighter than protons that neutrinos were postulated to have vanishing mass until the discovery of neutrino flavour oscillations2 proved otherwise. But knowing that neutrinos have mass and actually measuring what it is are two entirely different things. Now, writing in Nature Physics, the KATRIN Collaboration reports that it has constrained the mass of the electron antineutrino to be less than one-billionth of the proton mass3.

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Fig. 1: Effect of the neutrino mass on the beta decay spectrum.

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Authors and Affiliations

  1. Department of Physics, University of Milano-Bicocca, Milan, Italy

    Angelo Nucciotti

  2. INFN Sezione di Milano Bicocca, Milan, Italy

    Angelo Nucciotti

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  1. Angelo Nucciotti
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Correspondence to Angelo Nucciotti.

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Nucciotti, A. Still too small to be measured. Nat. Phys. 18, 128–129 (2022). https://doi.org/10.1038/s41567-021-01495-7

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