Improved measurement of the positive muon anomalous magnetic moment

A new measurement of the positive muon's anomalous magnetic moment has been made at the Brookhaven Alternating Gradient Synchrotron using the direct injection of polarized muons into the superferric storage ring. The angular frequency difference ${\ensuremath{\omega}}_{a}$ between the angular spin precession frequency ${\ensuremath{\omega}}_{s}$ and the angular orbital frequency ${\ensuremath{\omega}}_{c}$ is measured as well as the free proton NMR frequency ${\ensuremath{\omega}}_{p}.$ These determine $R={\ensuremath{\omega}}_{a}/{\ensuremath{\omega}}_{p}=3.707201(19)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}.$ With ${\ensuremath{\mu}}_{\ensuremath{\mu}}/{\ensuremath{\mu}}_{p}=3.18334539(10)$ this gives ${a}_{{\ensuremath{\mu}}^{+}}=11659191(59)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ $(\ifmmode\pm\else\textpm\fi{}5 \mathrm{ppm}),$ in good agreement with the previous CERN and BNL measurements for ${\ensuremath{\mu}}^{+}$ and ${\ensuremath{\mu}}^{\ensuremath{-}},$ and with the standard model prediction.