arXiv · 1712.00884
New result for the neutron $\beta$-asymmetry parameter $A_0$ from UCNA
Abstract
The neutron $\beta$-decay asymmetry parameter $A_0$ defines the correlation between the spin of the neutron and the momentum of the emitted electron, which determines $\lambda=\frac{g_{A}}{g_{V}}$, the ratio of the axial-vector to vector weak coupling constants. The UCNA Experiment, located at the Ultracold Neutron facility at the Los Alamos Neutron Science Center, is the first to measure such a correlation coefficient using ultracold neutrons (UCN). Following improvements to the systematic uncertainties and increased statistics, we report the new result $A_0 = -0.12054(44)_{\mathrm{stat}}(68)_{\mathrm{syst}}$ which yields $\lambda\equiv \frac{g_{A}}{g_{V}}=-1.2783(22)$. Combination with the previous UCNA result and accounting for correlated systematic uncertainties produces $A_0=-0.12015(34)_{\mathrm{stat}}(63)_{\mathrm{syst}}$ and $\lambda\equiv \frac{g_{A}}{g_{V}}=-1.2772(20)$.
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M. A. -P. Brown, E. B. Dees, E. Adamek, B. Allgeier, M. Blatnik, T. J. Bowles, L. J. Broussard, R. Carr, S. Clayton, C. Cude-Woods, S. Currie, X. Ding, B. W. Filippone, A. Garcia, P. Geltenbort, S. Hasan, K. P. Hickerson, J. Hoagland, R. Hong, G. E. Hogan, A. T. Holley, T. M. Ito, A. Knecht, C. -Y. Liu, J. Liu, M. Makela, J. W. Martin, D. Melconian, M. P. Mendenhall, S. D. Moore, C. L. Morris, S. Nepal, N. Nouri, R. W. Pattie, Jr., A. Perez-Galvan, D. G. Phillips II, R. Picker, M. L. Pitt, B. Plaster, J. C. Ramsey, R. Rios, D. J. Salvat, A. Saunders, W. Sondheim, S. J. Seestrom, S. Sjue, S. Slutsky, X. Sun, C. Swank, G. Swift, E. Tatar, R. B. Vogelaar, B. VornDick, Z. Wang, J. Wexler, T. Womack, C. Wrede, A. R. Young, B. A. Zeck. 2017-12-04. New result for the neutron $\beta$-asymmetry parameter $A_0$ from UCNA. https://doi.org/10.1103/physrevc.97.035505
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