Search for dark matter decay of the free neutron from the UCNA experiment: $n\to \chi +e^{+}{e}^{–}$

Journal Article · 21 May 2018 · Physical Review C

DOI: https://doi.org/10.1103/PhysRevC.97.052501 · OSTI ID:1439426

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.; Mendenhall, M. P.; Moore, S. D.; Morris, C. L.; Nepal, S.; Nouri, N.; Pattie, R. W.; Pérez Galván, A.; Phillips, D. G.; Picker, R.; Pitt, M. L.; Plaster, B.; Ramsey, J. C.; Rios, R.; Salvat, D. J.; Saunders, A.; Sondheim, W.; Sjue, S.; Slutsky, S.; Swank, C.; Swift, G.; Tatar, E.; Vogelaar, R. B.; VornDick, B.; Wang, Z.; Wei, W.; Wexler, J.; Womack, T.; Wrede, C.; Young, A. R.; Zeck, B. A.

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.

• Research Organization: Univ. of Kentucky, Lexington, KY (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE
• Contributing Organization: UCNA Collaboration
• Grant/Contract Number: SC0014622; FG02-08ER41557; FG02-97ER41042; 20110043DR; AC05-00OR22725; 89233218CNA000001
• OSTI ID: 1439426
• Alternate ID(s): OSTI ID: 1438065; OSTI ID: 1481650; OSTI ID: 1525826
• Report Number(s): LA-UR-18-22249; PRVCAN; DE-FG02-97ER41042; TRN: US1900608
• Journal Information: Physical Review C, Vol. 97, 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 = {https://link.aps.org/doi/10.1103/PhysRevC.97.035505}}; ISSN 2469-9985
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English