New Measurement of the Anomalous Magnetic Moment of the Positive Muon

Abstract
The muon anomalous magnetic moment has been measured in a new experiment at Brookhaven. Polarized muons were stored in a superferric ring, and the angular frequency difference, ωa, between the spin precession and orbital frequencies was determined by measuring the time distribution of high-energy decay positrons. The ratio R of ωa to the Larmor precession frequency of free protons, ωp, in the storage-ring magnetic field was measured. We find R=3.707220(48)×103. With μμ/μp=3.18334547(47) this gives aμ+=1165925(15)×109 ( ±13ppm), in good agreement with the previous CERN measurements for μ+ and μ and of approximately the same precision.