Medium Energy Particle Physics - Muonium/RHIC - SPIN

Abstract

This grant enabled research from 1991 to 2001 on muonium, the bound state of a positive muon and electron. The effort was led by Vernon Hughes, and involved almost 20 physicists from four U.S. and two international institutions. The experiment E1054 performed under the grant at the Clinton P. Anderson Meson Physics Facility at Los Alamos, was both a continuation and improvement on a series of experiments dating back to the discovery of muonium in 1960. High precision measurements of two Zeeman hyperfine transitions in the ground state of muonium were made, using microwave magnetic resonance spectroscopy and a line-narrowing technique. The experiment yielded the most precise values for the ground state hyperfine interval, {Delta}v, to 12 ppb, and the ratio of muon to proton magnetic moments, {mu}{sub {mu}}/{mu}{sub p} to 120 ppb, representing a threefold (statistics limited) improvement over previous work. The mass of the muon, m{sub {mu}}, is also determined most precisely from this work. Comparison between theory and experiment for {Delta}v constitutes the most precise test of bound-state QED, and also tests {mu}e universality. Using the theoretical predictions for {Delta}v, a value of the fine structure constant {alpha} was derived to 58 ppb. Finally, by searching for sidereal variations in the transition frequencies, limits were placed on the muon parameters of theoretical extensions of the standard model allowing CPT and Lorentz violation.