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

Sun, X. and Blatnik, M. and Carr, R. and Filippone, B. W. and Hickerson, K. P. and Martin, J. W. and Mendenhall, M. P. and Pérez Galván, A. and Picker, R. and Slutsky, S. and Swank, C. and Wei, W. (2018) Search for dark matter decay of the free neutron from the UCNA experiment: n → χ + e^+e^−. Physical Review C, 97 (5). Art. No. 052501. ISSN 2469-9985.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sun, X.0000-0001-8817-4643
Filippone, B. W.0000-0002-2618-2688
Hickerson, K. P.0000-0001-7647-119X
Wei, W.0000-0002-9670-4787
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.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-08ER41557
Department of Energy (DOE)DE-SC0014622
Department of Energy (DOE)DE-FG02-97ER41042
Los Alamos National Laboratory20110043DR
Issue or Number:5
Record Number:CaltechAUTHORS:20180507-101822389
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86242
Deposited By: Tony Diaz
Deposited On:07 May 2018 17:28
Last Modified:09 Mar 2020 13:18

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