1998/09/29 by I. S. Towner, I.S. Towner, Towner, I. S. +2
Physics and Astronomy · #Atomic and Subatomic Physics Research #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Nuclear Experiment (nucl-ex) #Nuclear Theory (nucl-th) #Nuclear physics research studies #Particle physics theoretical and experimental studies #hep-ph #nucl-ex #nucl-th
paper · pdf · doi:10.48550/arxiv.nucl-th/9809087
22 pages, LaTeX with sprocl.sty and epsf.sty; Talk at WEIN98: Physics beyond the standard model, Santa Fe, June 1998
arxiv created 1998/09/29 · openalex publication_date 1998/09/29 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The value of the Vud matrix element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix can be derived from nuclear superallowed beta decays, neutron decay, and pion beta decay. We survey current world data for all three. Today, the most precise value of Vud comes from the nuclear decays; however, the precision is limited not by experimental error but by the estimated uncertainty in theoretical corrections. The neutron data are approximately a factor of four poorer in precision but this could change dramatically in the near future as planned experiments come to fruition. The nuclear result (and the most recent of the neutron decay results) differ at the 98% confidence level from the unitarity condition for the CKM matrix. We examine the reliability of the small calculated corrections that have been applied to the data, and assess the likelihood of even higher quality nuclear data becoming available to confirm or deny the discrepancy. Some of the required experiments depend upon the availability of intense radioactive beams. Others are possible today.