Direct experimental constraints on the spatial extent of a neutrino wavepacket

• 成果类型: Article
• 署名作者: Smolsky, Joseph; Leach, Kyle G.; Abells, Ryan; Amaro, Pedro; Andoche, Adrien; Borbridge, Keith; Bray, Connor; Cantor, Robin; Diercks, David; Fretwell, Spencer; Friedrich, Stephan; Gillespie, Abigail; Guerra, Mauro; Hall, Ad; Harris, Cameron N.; Harris, Jackson T.; Hayen, Leendert M.; Hervieux, Paul-Antoine; Hinkle, Calvin; Kim, Geon-Bo; Kim, Inwook; Lamm, Amii; Lennarz, Annika; Lordi, Vincenzo; Machado, Jorge; Marino, Andrew; Mckeen, David; Mougeot, Xavier; Ponce, Francisco; Ruiz, Chris; Samanta, Amit; Santos, Jose Paulo; Stone-Whitehead, Caitlyn; Taylor, John; Templet, Joseph; Upadhyayula, Sriteja; Wagner, Louis; Warburton, William K.
• 署名单位: Colorado School of Mines; Michigan State University; University of British Columbia; Centre National de la Recherche Scientifique (CNRS); CNRS - Institute of Physics (INP); Universites de Strasbourg Etablissements Associes; Universite de Strasbourg; United States Department of Energy (DOE); Lawrence Livermore National Laboratory; Colorado School of Mines; Universite de Caen Normandie; McMaster University; Universite Paris Saclay; CEA; United States Department of Energy (DOE); Pacific Northwest National Laboratory
• 刊物名称: Nature
• ISSN/ISSBN: 0028-2281
• DOI: 10.1038/s41586-024-08479-6
• 发表日期: 2025-02-20
• 关键词: oscillation

摘要

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 contested1, 2, 3-4 and the spatial extent of the neutrino wavepacket is only loosely constrained by reactor neutrino oscillation data with a spread of 13 orders of magnitude5,6. 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.