Article Dans Une Revue Nature Année : 2025

Direct experimental constraints on the spatial extent of a neutrino wavepacket

Joseph Smolsky
Ryan Abells
  • Fonction : Auteur
Connor Bray
David Diercks
Ad Hall
  • Fonction : Auteur
Jackson T Harris
  • Fonction : Auteur
Inwook Kim
Annika Lennarz
Vincenzo Lordi
Andrew Marino
David Mckeen
  • Fonction : Auteur
Francisco Ponce
Chris Ruiz
John Taylor
Sriteja Upadhyayula
Louis Wagner
William K Warburton
  • Fonction : Auteur

Résumé

Despite their high relative abundance in our Universe, neutrinos are the least understood fundamental particles of nature. In fact, the quantum properties of neutrinos emitted in experimentally relevant sources are theoretically contested and the spatial extent of the neutrino wavepacket is only loosely constrained by reactor neutrino oscillation data with a spread of 13 orders of magnitude. Here we present a method to directly access this quantity by precisely measuring the energy width of the recoil daughter nucleus emitted in the radioactive decay of beryllium-7. The final state in the decay process contains a recoiling lithium-7 nucleus, which is entangled with an electron neutrino at creation. The lithium-7 energy spectrum is measured to high precision by directly embedding beryllium-7 radioisotopes into a high-resolution superconducting tunnel junction that is operated as a cryogenic sensor. Under this approach, we set a lower limit on the Heisenberg spatial uncertainty of the recoil daughter of 6.2 pm, which implies that the final-state system is localized at a scale more than a thousand times larger than the nucleus itself. From this measurement, the first, to our knowledge, direct lower limit on the spatial extent of a neutrino wavepacket is extracted. These results may have implications in several areas including the theoretical understanding of neutrino properties, the nature of localization in weak nuclear decays and the interpretation of neutrino physics data.
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Dates et versions

cea-04951540 , version 1 (17-02-2025)

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Joseph Smolsky, Kyle G Leach, Ryan Abells, Pedro Amaro, Adrien Andoche, et al.. Direct experimental constraints on the spatial extent of a neutrino wavepacket. Nature, 2025, ⟨10.1038/s41586-024-08479-6⟩. ⟨cea-04951540⟩
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