Search for the Neutron Decay n$\rightarrow$ X+$\gamma$ where X is a dark matter particle

• Published in: Physical review letters 2018, Vol.121 (2)
• Main Authors: Tang, Z., Blatnik, M., Broussard, L.J., Choi, J.H., Clayton, S.M., Cude-Woods, C., Currie, S., Fellers, D.E., Fries, E.M., Geltenbort, P., Gonzalez, F., Ito, T.M., Liu, C.Y., Macdonald, S.W.T., Makela, M., Morris, C.L., O'Shaughnessy, C.M., Pattie, R.W., Plaster, B., Salvat, D.J., Saunders, A., Wang, Z., Young, A.R., Zeck, B.A.
• Format: Article
• Language: English
• Subjects: Nuclear Experiment; Physics
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.121.022505

Fornal and Grinstein recently proposed that the discrepancy between two different methods of neutron lifetime measurements, the beam and bottle methods, can be explained by a previously unobserved dark matter decay mode, n→X+γ. We perform a search for this decay mode over the allowed range of energies of the monoenergetic γ ray for X to be dark matter. A Compton-suppressed high-purity germanium detector is used to identify γ rays from neutron decay in a nickel-phosphorous-coated stainless-steel bottle. A combination of Monte Carlo and radioactive source calibrations is used to determine the absolute efficiency for detecting γ rays arising from the dark matter decay mode. We exclude the possibility of a sufficiently strong branch to explain the lifetime discrepancy with 97% confidence.