Direct Measurement of the Proton Magnetic Moment

Abstract

The proton magnetic moment in nuclear magnetons is measured to be ${\mu }_p/{\mu }_N\equiv g/2=2.792846\pm 0.000007$, a 2.5 parts per million uncertainty. The direct determination, using a single proton in a Penning trap, demonstrates the first method that should work as well with an antiproton ($\overline{p}$) as with a proton ($p$). This opens the way to measuring the $\overline{p}$ magnetic moment (whose uncertainty has essentially not been reduced for 20 years) at least ${10}^3$ times more precisely.