Precision Mass Spectroscopy of the Antiproton and Proton Using Simultaneously Trapped Particles

Abstract

This last of a series of three measurements improves the comparison of antiproton $(\overline{p})$ and proton $(p)$ by almost a factor of ${10}^{6}$ over earlier exotic atom measurements, and is the most precise $\mathrm{CPT}$ test with baryons by a similar large factor. Measuring the cyclotron frequencies of a simultaneously trapped $\overline{p}$ and ${H}^{\ensuremath{-}}$ ion establishes that the ratio of $q/m$ for $\overline{p}$ and $p$ is $\ensuremath{-}0.99999999991\ifmmode\pm\else\textpm\fi{}0.00000000009$, more than 10 times the accuracy over our previous measurement. This $9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ comparison makes the first use of simultaneously trapped particles for sub-ppb spectroscopy.