A Caltech Library Service

Improved Neutron Lifetime Measurement with UCNτ

Gonzalez, F. M. and Fries, E. M. and Cude-Woods, C. and Bailey, T. and Blatnik, M. and Broussard, L. J. and Callahan, N. B. and Choi, J. H. and Clayton, S. M. and Currie, S. A. and Dawid, M. and Dees, E. B. and Filippone, B. W. and Fox, W. and Geltenbort, P. and George, E. and Hayen, L. and Hickerson, K. P. and Hoffbauer, M. A. and Hoffman, K. and Holley, A. T. and Ito, T. M. and Komives, A. and Liu, C.-Y. and Makela, M. and Morris, C. L. and Musedinovic, R. and O’Shaughnessy, C. and Pattie, R. W. and Ramsey, J. and Salvat, D. J. and Saunders, A. and Sharapov, E. I. and Slutsky, S. and Su, V. and Sun, X. and Swank, C. and Tang, Z. and Uhrich, W. and Vanderwerp, J. and Walstrom, P. and Wang, Z. and Wei, W. and Young, A. R. (2021) Improved Neutron Lifetime Measurement with UCNτ. Physical Review Letters, 127 (16). Art. No. 162501. ISSN 0031-9007. doi:10.1103/physrevlett.127.162501.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.


Use this Persistent URL to link to this item:


We report an improved measurement of the free neutron lifetime τ_n using the UCNτ apparatus at the Los Alamos Neutron Science Center. We count a total of approximately 38 × 10⁶ surviving ultracold neutrons (UCNs) after storing in UCNτ’s magnetogravitational trap over two data acquisition campaigns in 2017 and 2018. We extract τ_n from three blinded, independent analyses by both pairing long and short storage time runs to find a set of replicate τ_n measurements and by performing a global likelihood fit to all data while self-consistently incorporating the β-decay lifetime. Both techniques achieve consistent results and find a value τ_n = 877.75 ± 0.28_(stat) + 0.22/−0.16_(syst) s. With this sensitivity, neutron lifetime experiments now directly address the impact of recent refinements in our understanding of the standard model for neutron decay.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper InPhysics : Viewpoint
Fries, E. M.0000-0002-3788-8096
Blatnik, M.0000-0003-3496-0010
Filippone, B. W.0000-0002-2618-2688
Hickerson, K. P.0000-0001-7647-119X
Salvat, D. J.0000-0002-0556-5436
Sun, X.0000-0001-8817-4643
Wei, W.0000-0002-9670-4787
Alternate Title:An improved neutron lifetime measurement with UCNτ
Additional Information:© 2021 American Physical Society. (Received 18 June 2021; accepted 20 July 2021; published 13 October 2021) This work is supported by the LANL 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. 1506459, No. 1553861, No. 1812340, No. 1714461, and No. 1913789; and NIST precision measurements grant.
Funding AgencyGrant Number
Los Alamos National LaboratoryUNSPECIFIED
Department of Energy (DOE)DE-FG02-ER41042
Department of Energy (DOE)DE-AC52-06NA25396
Department of Energy (DOE)DE-AC05-00OR2272
Department of Energy (DOE)89233218CNA000001
National Institute of Standards and Technology (NIST)UNSPECIFIED
Issue or Number:16
Record Number:CaltechAUTHORS:20211014-212143728
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111450
Deposited By: George Porter
Deposited On:18 Oct 2021 22:23
Last Modified:18 Oct 2021 22:23

Repository Staff Only: item control page