New Measurement of the Anomalous Magnetic Moment of the Positive Muon

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 R0ex0ex=0ex0ex3.707220(48)×10^-3. With μ_μ/μₚ0ex0ex=0ex0ex3.18334547(47) this gives a_μ⁺0ex0ex=0ex0ex1165925(15)×10^-9 ( ±13ppm), in good agreement with the previous CERN measurements for μ⁺ and μ^- and of approximately the same precision.