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Published May 2018 | Published + Submitted
Journal Article Open

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

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 (UCNs). 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 ≫ 5σlevel for 100 keV < E_(e^+e^−) < 644 keV. 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.

Additional Information

© 2018 American Physical Society. Received 30 March 2018; published 21 May 2018. We are grateful for helpful discussions with B. Grinstein. 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.

Attached Files

Published - PhysRevC.97.052501.pdf

Submitted - 1803.10890.pdf

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August 19, 2023
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