Antiprotons Reflect a Magnetic Symmetry

Physicists have improved the measurement of the antiproton magnetic dipole moment, further narrowing how close to identical it is in magnitude (with opposite sign) to the proton value. I ran across a number of poor articles describing this experiment, all obviously cribbing from the same press release. One mentioned magnetic charge, another claimed that that the experiment determined the charge of an antiproton and seemed to confuse the Penning trap and the proton beam at the LHC. One put the emphasis on the act of trapping antiprotons, as if this had not been done before (it has).

This is a good one. There’s also a link to the free PRL.

[The ATRAP collaboration] look for a difference in the magnetic moments of the proton and antiproton. To enable this test, they precisely measure the magnetic moment of a single, trapped antiproton, achieving the most sensitive measurement to date of this quantity. They compare their result to the known value of the proton’s magnetic moment and find that the magnitudes are equal within experimental uncertainty, as predicted by the CPT theorem. Though there have been other tests of CPT with better precision overall, the work reported by ATRAP improves the limits on CPT violation in the difference of the proton and antiproton magnetic moments by nearly three orders of magnitude