Improved limits on Fierz Interference using asymmetry measurements from the UCNA experiment

• Published in: arXiv.org
• Main Authors: Sun, Xuan, Adamek, E, Allgeier, B, Bagdasarova, Y, Berguno, D B, Blatnik, M, Bowles, T J, Broussard, L J, Brown, M A -P, Carr, R, Clayton, S, Cude-Woods, C, Currie, S, Dees, E B, Ding, X, Filippone, B W, García, A, Geltenbort, P, Hasan, S, Hickerson, K P, Hoagland, J, Hong, R, Holley, A T, Ito, T M, Knecht, A, C -Y Liu, Liu, J, Makela, M, Mammei, R, Martin, J W, Melconian, D, Mendenhall, M P, Moore, S D, Morris, C L, Nepal, S, Nouri, N, Pattie, R W, A Pérez Galván, Phillips, D G, Picker, R, Pitt, M L, Plaster, B, Salvat, D J, Saunders, A, Sharapov, E I, Sjue, S, Slutsky, S, Sondheim, W, Swank, C, Tatar, E, Vogelaar, R B, VornDick, B, Wang, Z, Wei, W, Wexler, J W, Womack, T, Wrede, C, Young, A R, Zeck, B A
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 13.11.2019
• Subjects: Asymmetry; Beta decay; Confidence intervals; Datasets; Decay rate; Dependence; Experiments; Interference; Neutron decay; Neutrons; Physics - Nuclear Experiment; Systematic errors
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1911.05829

The Ultracold Neutron Asymmetry (UCNA) experiment was designed to measure the \(\beta\)-decay asymmetry parameter, \(A_0\), for free neutron decay. In the experiment, polarized ultracold neutrons are transported into a decay trap, and their \(\beta\)-decay electrons are detected with \(\approx 4\pi\) 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 \(\beta\)-decay rate. In this work, we determine \(b_{n}\) from the energy dependence of \(A_0\) 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 \(b_{n} = 0.066 \pm 0.041_{\text{stat}} \pm 0.024_{\text{syst}}\) which corresponds to a limit of \(-0.012 < b_{n} < 0.144\) at the 90% confidence level.