9214998 Minehart This award supports Professors Ralph Minehart and Klaus Ziock of the University of Virginia, plus two of their postdoctoral associates, to collaborate in research with Dr. Reinhart Frosch of the Particle and Nuclear Physics Department of the Paul Scherrer Institute (PSI) in Villagen, Switzerland. Using an experimental method proposed and developed by the U.S. group, these investigators plus five other research groups are engaged in a multinational cooperative effort to study the rate of charged pion beta decay to neutral pion. Each of the seven groups, including the two from the former Soviet Union, is responsible for the detailed design and construction (and cost) of a specific component of a novel and highly specialized Cesium Iodide-based detector to be installed at PSI. This apparatus will make it possible to obtain measurements of pion beta decay to an accuracy of .5 percent by 1995; the previous limit of accuracy was around 3%. The experiment will determine elements of the fundamental mixing matrix which relates transitions between different quark generations. Pion beta decay is one of the fundamental semileptonic weak interaction processes. It provides the theoretically least ambiguous means to study weak quark mixing. Achieving the greatly improved accuracy of measurement hoped for in this project will enable the participants to test quark-lepton universality. The resulting accurate measurements will have an impact on weak interaction theory and on the standard model of hadronic structure at a fundamental level. This multinational experiment is far more than any one or two of the participating groups could accomplish alone. The combination of the many groups will also make mutually beneficial use of special resources that can be provided by the groups from the former Soviet Union. ***
