skip to main content


This content will become publicly available on May 21, 2019

Title: Search for dark matter decay of the free neutron from the UCNA experiment: n χ + e + e

It has been proposed recently that a previously unobserved neutron decay branch to a dark matter particle (χ) could account for the discrepancy in the neutron lifetime observed in experiments that use two different measurement techniques. One of the possible final states discussed includes a single χ along with an e +e pair. We use data from the UCNA (Ultracold Neutron Asymmetry) experiment to set limits on this decay channel. Coincident electron-like events are detected with ~4π acceptance using a pair of detectors that observe a volume of stored ultracold neutrons. The summed kinetic energy (E e+e) from such events is used to set limits, as a function of the χ mass, on the branching fraction for this decay channel. For χ masses consistent with resolving the neutron lifetime discrepancy, we exclude this as the dominant dark matter decay channel at >>5σ level for 100 < E e+e < 644keV. In conclusion, if the χ+e +e final state is not the only one, we set limits on its branching fraction of <10 –4 for the above E e+e range at >90% confidence level.
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; « less
Publication Date:
Grant/Contract Number:
SC0014622; FG02-08ER41557; FG02-97ER41042; 20110043DR
Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 97; Journal Issue: 5; Related Information: @article{PhysRevC.97.035505,title = {New result for the neutron $\ensuremath{\beta}$-asymmetry parameter ${A}_{0}$ from UCNA},author = {Brown, M. A.-P. and Dees, E. B. and Adamek, E. and Allgeier, B. and Blatnik, M. and Bowles, T. J. and Broussard, L. J. and Carr, R. and Clayton, S. and Cude-Woods, C. and Currie, S. and Ding, X. and Filippone, B. W. and Garc\'{\i}a, A. and Geltenbort, P. and Hasan, S. and Hickerson, K. P. and Hoagland, J. and Hong, R. and Hogan, G. E. and Holley, A. T. and Ito, T. M. and Knecht, A. and Liu, C.-Y. and Liu, J. and Makela, M. and Martin, J. W. and Melconian, D. and Mendenhall, M. P. and Moore, S. D. and Morris, C. L. and Nepal, S. and Nouri, N. and Pattie, R. W. and P\'erez Galv\'an, A. and Phillips, D. G. and Picker, R. and Pitt, M. L. and Plaster, B. and Ramsey, J. C. and Rios, R. and Salvat, D. J. and Saunders, A. and Sondheim, W. and Seestrom, S. J. and Sjue, S. and Slutsky, S. and Sun, X. and Swank, C. and Swift, G. and Tatar, E. and Vogelaar, R. B. and VornDick, B. and Wang, Z. and Wexler, J. and Womack, T. and Wrede, C. and Young, A. R. and Zeck, B. A.},collaboration = {UCNA Collaboration},journal = {Phys. Rev. C},volume = {97},issue = {3},pages = {035505},numpages = {9},year = {2018},month = {Mar},publisher = {American Physical Society},doi = {10.1103/PhysRevC.97.035505},url = {}}; Journal ID: ISSN 2469-9985
American Physical Society (APS)
Research Org:
Univ. of Kentucky, Lexington, KY (United States)
Sponsoring Org:
Contributing Orgs:
UCNA Collaboration
Country of Publication:
United States
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Neutron decay; dark matter decay; neutron to dark matter decay channel; neutron producing positron-electron pairs
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1438065