1. First Observation of $P$-odd $��$ Asymmetry in Polarized Neutron Capture on Hydrogen
- Author
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Blyth, D., Fry, J., Fomin, N., Alarcon, R., Alonzi, L., Askanazi, E., Bae��ler, S., Balascuta, S., Barr��n-Palos, L., Barzilov, A., Bowman, J. D., Birge, N., Calarco, J. R., Chupp, T. E., Cianciolo, V., Coppola, C. E., Crawford, C. B., Craycraft, K., Evans, D., Fieseler, C., Frle��, E., Garishvili, I., Gericke, M. T. W., Gillis, R. C., Grammer, K. B., Greene, G. L., Hall, J., Hamblen, J., Hayes, C., Iverson, E. B., Kabir, M. L., Kucuker, S., Lauss, B., Mahurin, R., McCrea, M., Maldonado-Vel��zquez, M., Masuda, Y., Mei, J., Milburn, R., Mueller, P. E., Musgrave, M., Nann, H., Novikov, I., Parsons, D., Penttil��, S. I., Po��ani��, D., Ramirez-Morales, A., Root, M., Salas-Bacci, A., Santra, S., Schr��der, S., Scott, E., Seo, P. -N., Sharapov, E. I., Simmons, F., Snow, W. M., Sprow, A., Stewart, J., Tang, E., Tang, Z., Tong, X., Turkoglu, D. J., Whitehead, R., and Wilburn, W. S.
- Subjects
High Energy Physics - Experiment (hep-ex) ,FOS: Physical sciences ,Nuclear Experiment (nucl-ex) - Abstract
We report the first observation of the parity-violating 2.2 MeV gamma-ray asymmetry $A^{np}_��$ in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. $A^{np}_��$ isolates the $��I=1$, \mbox{$^{3}S_{1}\rightarrow {^{3}P_{1}}$} 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 EFT. We measured $A^{np}_��= [-3.0 \pm 1.4 (stat) \pm 0.2 (sys)]\times 10^{-8}$, which implies a DDH weak $��NN$ coupling of $h_��^{1} = [2.6 \pm 1.2(stat) \pm 0.2(sys)] \times 10^{-7}$ and a pionless EFT constant of $C^{^{3}S_{1}\rightarrow ^{3}P_{1}}/C_{0}=[-7.4 \pm 3.5 (stat) \pm 0.5 (sys)] \times 10^{-11}$ MeV$^{-1}$. We describe the experiment, data analysis, systematic uncertainties, and the implications of the result., 6 pages, 5 figures
- Published
- 2018
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