Editing Proton (section)

== Antiproton ==
{{Main|Antiproton}}
[[CPT-symmetry]] puts strong constraints on the relative properties of particles and [[antiparticle]]s and, therefore, is open to stringent tests. For example, the charges of a proton and antiproton must sum to exactly zero. This equality has been tested to one part in {{val|e=8}}. The equality of their masses has also been tested to better than one part in {{val|e=8}}. By holding antiprotons in a [[Penning trap]], the equality of the charge-to-mass ratio of protons and antiprotons has been tested to one part in {{val|6|e=9}}.<ref name="Gabrielse2006" /> The [[magnetic moment]] of antiprotons has been measured with an error of {{val|8|e=-3}} nuclear [[Bohr magneton]]s, and is found to be equal and opposite to that of a proton.<ref>{{Cite web |title=BASE precisely measures antiproton's magnetic moment |url=https://home.cern/news/news/physics/base-precisely-measures-antiprotons-magnetic-moment |access-date=2022-03-04 |website=CERN |language=en |archive-date=2022-03-04 |archive-url=https://web.archive.org/web/20220304125452/https://home.cern/news/news/physics/base-precisely-measures-antiprotons-magnetic-moment |url-status=live }}</ref>