Study of neutron beta decay with the Nab experiment

¹ Department of Physics, University of Virginia, Charlottesville, VA 22904–4714, USA
² Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
³ Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506, USA
⁴ Department of Physics, Arizona State University, Tempe, AZ 85287–1504, USA
⁵ Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
⁶ Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA
⁷ University of Michigan, Ann Arbor, MI 48109, USA
⁸ Massachusetts Institute of Technology, Cambridge, MA 02139, USA
⁹ Department of Physics, Geosciences, and Astronomy, Eastern Kentucky University, Richmond, KY 40475, USA
¹⁰ Department of Physics, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada
¹¹ Department of Chemistry and Physics, MC 2252, University of Tennessee-Chattanooga, Chattanooga, TN 37403, USA
¹² LPC Caen, ENSICAEN, Université de Caen, CNRS/IN2P3, Caen, France
¹³ PACE, Georgia Institute of Technology, Atlanta, GA 30332, USA
¹⁴ Los Alamos National Laboratory, Los Alamos, NM 87545, USA
¹⁵ Department of Physics, University of Winnipeg, Winnipeg, Manitoba R3B2E9, Canada
¹⁶ Department of Physics, Centre College of Kentucky, Danville, KY 40422

^* e-mail: baessler@virginia.edu

Published online: 25 September 2024

Abstract

The current three sigma tension in the unitarity test of the Cabbibo-Kobayashi-Maskawa (CKM) matrix is a notable problem with the Standard Model of elementary particle physics. A long-standing goal of the study of free neutron beta decay is to better determine the CKM element V_ud through measurements of the neutron lifetime and a decay correlation parameter. The Nab collaboration intends to measure a, the neutrino-electron correlation, with accuracy sufficient for a competitive evaluation of V_ud based on neutron decay data alone. This paper gives a status report and an outlook.