Anomalous magnetic moment of the muon and hyperfine structure and Zeeman effect in ground state muonium

Abstract

The aim of the ongoing muon g-2 experiment at Brookhaven National Laboratory (BNL) to measure a/sub /spl mu// to 0.35 ppm represents a factor of 20 improvement over the current value obtained from the latest CERN experiment. This projected precision would allow us to determine the electroweak contribution, involving single loop Feynman diagrams of W, Z and Higgs scalar particle, to a/sub /spl mu// with an accuracy of about 20%. Coupled with improvements in the QED theoretical calculation for a/sub /spl mu// and the completion of associated experiments needed to improve the calculation of the hadronic contribution to a/sub /spl mu//, a comparison of a/sub /spl mu//(expt) and a/sub /spl mu//(theor) will provide a sensitive test of the standard model concerning renormalizability of the electroweak theory, and to search for physics beyond the standard model with high sensitivity especially for investigating lepton substructures, which would be complementary to the current and future high energy collider experiments including LHC and LEP II. A new high precision measurement of the muonium (/spl mu//sup +/e/sup -/) hyperfine structure interval /spl Delta//spl nu/ and its Zeeman effect in the ground state which gives the muon magnetic moment is being undertaken at the Los Alamos Meson Physics Facility (LAMPF). The goal of the experiment is to measure the ratio of the magnetic moments of muon and proton to a fractional accuracy of 60 parts per billion (ppb), and the muonium hyperfine structure interval in the ground state, /spl Delta//spl nu/, to 10 ppb. These measurements will improve our knowledge of /spl mu//sub /spl mu////spl mu//sub p/ and /spl Delta//spl nu/ by a factor of about 5. With the improved accuracy in /spl mu//sub /spl mu////spl mu//sub p/ to 60 ppb from LAMPF, /spl Delta//spl nu//sub expt/ and /spl Delta//spl nu//sub theor/ could be compared at about the 65 ppb level. This would be the most precise test of a two-lepton bound state system and of bound state QED in general. Alternatively, the fine structure constant a could be determined at the 30 ppb level. A precise value for /spl mu//sub /spl mu////spl mu//sub p/ is needed for the determination of the anomalous g-factor from the new Brookhaven muon g-2 experiment. New values for electric charges of positive and negative muons and the magnetic moment of the negative muon will be presented. The experiment to determine the anomalous magnetic moment of the muon is being prepared by the Muon (g-2) Collaboration. The muonium experiment is being carried out by collaborators from the Experiment 1054 at LAMPF. The status of the two experiments will be described. >