Abstract
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 (Ee+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 < Ee+e− < 644keV. 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 Ee+e− range at > 90% confidence level.
Document Type
Article
Publication Date
5-21-2018
Digital Object Identifier (DOI)
https://doi.org/10.1103/PhysRevC.97.052501
Funding Information
This work is supported in part by the US Department of Energy, Office of Nuclear Physics (DE-FG02-08ER41557, DE-SC0014622, DE-FG02-97ER41042) and the National Science Foundation (NSF-1002814, NSF-1005233, NSF-1102511, NSF-1205977, NSF-1306997, NSF-1307426, NSF-1506459, and NSF-1615153). We gratefully acknowledge the support of the LDRD program (20110043DR) and the AOT division of the Los Alamos National Laboratory.
Repository Citation
Sun, X.; Adamek, E.; Allgeier, B.; Blatnik, M.; Bowles, T. J.; Broussard, L. J.; Brown, M. A. -P.; Carr, R.; Clayton, S.; Cude-Woods, C.; Currie, S.; Dees, E. B.; Ding, X.; Filippone, B. W.; García, A.; Geltenbort, P.; Hasan, S.; Hickerson, K. P.; Hoagland, J.; Hong, R.; Hogan, G. E.; Holley, A. T.; Ito, T. M.; Knecht, A.; Liu, C. -Y.; Liu, J.; Makela, M.; Mammei, R.; Martin, J. W.; Melconian, D.; Nepal, Subash C.; and Plaster, Bradley R., "Search for Dark Matter Decay of the Free Neutron from the UCNA Experiment: n → χ + e+e−" (2018). Physics and Astronomy Faculty Publications. 569.
https://uknowledge.uky.edu/physastron_facpub/569
Notes/Citation Information
Published in Physical Review C, v. 97, issue 5, 052501, p. 1-5.
©2018 American Physical Society
The copyright holder has granted permission for posting the article here.
Due to the large number of authors, only the first 30 and the authors affiliated with the University of Kentucky are listed in the author section above. For the complete list of authors, please download this article or visit: https://doi.org/10.1103/PhysRevC.97.052501
This group of authors is collectively known as the UCNA Collaboration.