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, ${\omega }_a$, between the spin precession and orbital frequencies was determined by measuring the time distribution of high-energy decay positrons. The ratio $R$ of ${\omega }_a$ to the Larmor precession frequency of free protons, ${\omega }_p$, in the storage-ring magnetic field was measured. We find $R=3.707\mathrm{}220\left(48\right)\times {10}^{-3\mathrm{}}$. With ${\mu }_{\mu }/{\mu }_p=3.183\mathrm{}34547\left(47\right)$ this gives $a_{{\mu }^{+}}=1\mathrm{}165925\left(15\right)\times {10}^{-9\mathrm{}}$ ( $\pm 13\mathrm{ppm}$), in good agreement with the previous CERN measurements for ${\mu }^{+}$ and ${\mu }^{-}$ and of approximately the same precision.

• Received 12 October 1998

DOI:https://doi.org/10.1103/PhysRevLett.82.1632