This last of a series of three measurements improves the comparison of antiproton and proton by almost a factor of over earlier exotic atom measurements, and is the most precise test with baryons by a similar large factor. Measuring the cyclotron frequencies of a simultaneously trapped and ion establishes that the ratio of for and is , more than 10 times the accuracy over our previous measurement. This comparison makes the first use of simultaneously trapped particles for sub-ppb spectroscopy.
- Received 10 November 1998
©1999 American Physical Society