Published April 2025 | Version Published
Journal Article Open

Measurement of the free neutron lifetime in a magneto-gravitational trap with in situ detection

  • 1. ROR icon North Carolina State University
  • 2. ROR icon Indiana University
  • 3. ROR icon Los Alamos National Laboratory
  • 4. ROR icon Argonne National Laboratory
  • 5. ROR icon California Institute of Technology
  • 6. ROR icon Institut Laue-Langevin
  • 7. ROR icon Oak Ridge National Laboratory
  • 8. ROR icon Tennessee Technological University
  • 9. ROR icon DePauw University
  • 10. ROR icon University of Illinois Urbana-Champaign
  • 11. ROR icon East Tennessee State University
  • 12. ROR icon Joint Institute for Nuclear Research

Abstract

Here we publish three years of data from the UCNτ experiment performed at the Los Alamos Ultracold Neutron Facility at the Los Alamos Neutron Science Center. These data are in addition to our previously published data. Our goals in this paper are to better understand and quantify systematic uncertainties and to improve the lifetime statistical precision. We previously reported a value from our 2017–2018 data for the neutron lifetime of 877.75±0.28 (statistical) +0.22–0.16 (systematic) s. We have collected an additional three years of data reported here for the first time. When all the data from UCNτ are averaged for 2017, 2018, 2020, 2021, and 2022, we report an updated value for the lifetime of 877.83±0.22 (statistical)+0.20–0.17 (systematic) s. We utilized improved monitor detectors, reduced our correction due to UCN upscattering on residual gas, and employed four different UCN detector geometries both to reduce the correction required for rate dependence and to explore potential contributions due to phase space evolution.

Copyright and License

©2025 American Physical Society.

Acknowledgement

The authors thank the staff and management of the Los Alamos Neutron Science Center for providing the UCN used for these experiments and the Los Alamos LDRD program, the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Awards No. DE-FG02-ER41042, No. DE-AC52-06NA25396, No. DE-AC05-00OR2272, and No. 89233218CNA000001 under proposal LANLEEDM; NSF Grants No. 1614545, No. 1914133, No. 1553861, No. 2310015, No. 1812340, No. 1714461, No. 2110898, No. 1913789, No. 2209521, No. 2209481 and No. 2210341.

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PhysRevC.111.045501.pdf

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Additional details

Funding

Office of Nuclear Physics
DE-FG02-ER41042
Office of Nuclear Physics
DE-AC52-06NA25396
Office of Nuclear Physics
DE-AC05-00OR2272
Office of Nuclear Physics
LANLEEDM 89233218CNA000001
National Science Foundation
1614545
National Science Foundation
1914133
National Science Foundation
1553861
National Science Foundation
2310015
National Science Foundation
1812340
National Science Foundation
1714461
National Science Foundation
2110898
National Science Foundation
1913789
National Science Foundation
2209521
National Science Foundation
2209481
National Science Foundation
2210341

Dates

Accepted
2025-02-18
Accepted
Available
2025-04-07
Published online

Caltech Custom Metadata

Caltech groups
Division of Physics, Mathematics and Astronomy (PMA)
Publication Status
Published