Research in Intermediate Energy Physics

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

This project addresses certain fundamental aspects of the electroweak and strong interactions that are reflected in meson and nucleon properties and interactions at low/intermediate energies. The research is motivated by the fact that the present comprehensive theory--the Standard Model (SM)--is known to be incomplete; furthermore, the SM becomes unworkable for strong interactions at low energies. The rare beta decay of the pi-meson (pion), occurring once in about 100 million ordinary pion decays, provides a theoretically clean window to certain allowed extensions of the SM. The PIBETA experiment, mounted at the Paul Scherrer Institute, Switzerland, by an international collaboration of seven institutions led by the University of Virginia (UVa) group, aims to improve the present 4% accuracy of the pion beta decay rate by about a factor of ten in a staged approach, in order to match the theoretical uncertainty and provide new constraints on physics beyond the SM. Measurements that began in 1999 will continue through 2001. PIBETA is the main effort of the present research project. Additional commitments of effort include work on studies of nucleon and meson structure at Stanford (SLAC) and Jefferson Lab (CLAS collaboration). During the past three years this program has resulted in two doctoral degrees at UVa plus three more at collaborating universities stemming from the PIBETA project alone. Four more UVa Ph.D. degrees are expected in the next three to four years. Each year typically one to two undergraduate students are engaged in research on this project, thus gaining practical laboratory experience.