Search for dark matter decay of the free neutron from the UCNA experiment: n → X plus e+e-
Open Access
- 21 May 2018
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review C
- Vol. 97 (5), 052501
- https://doi.org/10.1103/PhysRevC.97.052501
Abstract
It has been proposed recently that a previously unobserved neutron decay branch to a dark matter particle (X) 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 X 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 similar to 4 pi 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 X mass, on the branching fraction for this decay channel. For X masses consistent with resolving the neutron lifetime discrepancy, we exclude this as the dominant dark matter decay channel at >> 5 sigma level for 100 < E-e+(e)- < 644 keV. If the X + e(+)e(-) final state is not the only one, we set limits on its branching fraction of 90% confidence level.Funding Information
- U.S. Department of Energy (DE-FG02-08ER41557, DE-SC0014622, DE-FG02-97ER41042)
- National Science Foundation (NSF-1002814, NSF-1005233, NSF-1102511, NSF-1205977, NSF-1306997, NSF-1307426, NSF-1506459, NSF-1615153)
- Laboratory Directed Research and Development (20110043DR)
- Los Alamos National Laboratory
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