Search for the Neutron Decay n→X+γ, Where X is a Dark Matter Particle

• Published in: Physical review letters Vol. 121; no. 2; p. 022505
• 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, Hickerson, K P, 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: Journal Article
• Language: English
• Published: United States American Physical Society 13-07-2018; American Physical Society (APS)
• Subjects: Dark matter; Measurement methods; Neutron decay; NUCLEAR PHYSICS AND RADIATION PHYSICS; Particle decay
• 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.