Improved limits on Fierz interference using asymmetry measurements from the Ultracold Neutron Asymmetry (UCNA) experiment
/ Authors
Xuan Sun, E. Adamek, B. Allgeier, Y. Bagdasarova, D. B. Berguño, Matej Blatnik, T. Bowles, L. Broussard, M. Brown, R. Carr
and 49 more authors
S. Clayton, C. Cude-Woods, S. Currie, E. Dees, X. Ding, B. Filippone, A. Garc'ia, P. Geltenbort, S. Hasan, K. Hickerson, J. Hoagland, R. Hong, A. Holley, T. Ito, A. Knecht, C-Y. Liu, J. Liu, M. Makela, R. Mammei, J. Martin, D. Melconian, M. Mendenhall, S. Moore, C. Morris, S. Nepal, N. Nouri, R. Pattie, A. Galv'an, D. Phillips, R. Picker, M. Pitt, B. Plaster, D. Salvat, A. Saunders, E. Sharapov, S. Sjue, S. Slutsky, W. Sondheim, C. Swank, E. Tatar, R. Vogelaar, B. Vorndick, Z. Wang, W. Wei, J. Wexler, T. Womack, C. Wrede, A. Young, B. Zeck
/ Abstract
The Ultracold Neutron Asymmetry (UCNA) experiment was designed to measure the β-decay asymmetry parameter, A₀, for free neutron decay. In the experiment, polarized ultracold neutrons are transported into a decay trap, and their β-decay electrons are detected with ≈4π acceptance into two detector packages which provide position and energy reconstruction. The experiment also has sensitivity to b_n, the Fierz interference term in the neutron β-decay rate. In this work, we determine b_n from the energy dependence of A₀ using the data taken during the UCNA 2011-2013 run. In addition, we present the same type of analysis using the earlier 2010 A dataset. Motivated by improved statistics and comparable systematic errors compared to the 2010 data-taking run, we present a new b_n measurement using the weighted average of our asymmetry dataset fits, to obtain b_n = 0.066±0.041_(stat)±0.024_(syst) which corresponds to a limit of −0.012 < b_n < 0.144 at the 90% confidence level.
Journal: Physical Review C