First Observation of P-odd γ Asymmetry in Polarized Neutron Capture on Hydrogen

Autor: D, Blyth, J, Fry, N, Fomin, R, Alarcon, L, Alonzi, E, Askanazi, S, Baeßler, S, Balascuta, L, Barrón-Palos, A, Barzilov, J D, Bowman, N, Birge, J R, Calarco, T E, Chupp, V, Cianciolo, C E, Coppola, C B, Crawford, K, Craycraft, D, Evans, C, Fieseler, E, Frlež, I, Garishvili, M T W, Gericke, R C, Gillis, K B, Grammer, G L, Greene, J, Hall, J, Hamblen, C, Hayes, E B, Iverson, M L, Kabir, S, Kucuker, B, Lauss, R, Mahurin, M, McCrea, M, Maldonado-Velázquez, Y, Masuda, J, Mei, R, Milburn, P E, Mueller, M, Musgrave, H, Nann, I, Novikov, D, Parsons, S I, Penttilä, D, Počanić, A, Ramirez-Morales, M, Root, A, Salas-Bacci, S, Santra, S, Schröder, E, Scott, P-N, Seo, E I, Sharapov, F, Simmons, W M, Snow, A, Sprow, J, Stewart, E, Tang, Z, Tang, X, Tong, D J, Turkoglu, R, Whitehead, W S, Wilburn
Rok vydání: 2018
Zdroj: Physical review letters. 121(24)
ISSN: 1079-7114
Popis: We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=[-3.0±1.4(stat)±0.2(syst)]×10^{-8}, which implies a DDH weak πNN coupling of h_{π}^{1}=[2.6±1.2(stat)±0.2(syst)]×10^{-7} and a pionless EFT constant of C^{^{3}S_{1}→^{3}P_{1}}/C_{0}=[-7.4±3.5(stat)±0.5(syst)]×10^{-11} MeV^{-1}. We describe the experiment, data analysis, systematic uncertainties, and implications of the result.
Databáze: OpenAIRE