Editing Antiproton (section)

=== Measurements ===
In July 2011, the [[ASACUSA]] experiment at CERN determined the mass of the antiproton to be {{val|1836.1526736|(23)}} times that of the electron.<ref name=Mhori>{{cite journal | journal=Nature | volume=475 |issue=7357 | pages=484–8 | date=2011 |last1=Hori |first1=M. |last2=Sótér | title=Two-photon laser spectroscopy of antiprotonic helium and the antiproton-to-electron mass ratio |doi=10.1038/nature10260 | first2=Anna | last3=Barna | first3=Daniel | last4=Dax | first4=Andreas | last5=Hayano | first5=Ryugo | last6=Friedreich | first6=Susanne | last7=Juhász | first7=Bertalan | last8=Pask | first8=Thomas | last9=Widmann | first9=Eberhard | display-authors=8| pmid=21796208| arxiv=1304.4330 | s2cid=4376768 }}</ref> This is the same as the mass of a proton, within the level of certainty of the experiment.

In October 2017, scientists working on the [[BASE experiment]] at CERN reported a measurement of the antiproton [[magnetic moment]] to a precision of 1.5 parts per billion.<ref name="TT-20171025">{{cite web |last=Adamson |first=Allan |title=Universe Should Not Actually Exist: Big Bang Produced Equal Amounts Of Matter And Antimatter |url=http://www.techtimes.com/articles/214821/20171025/universe-should-not-actually-exist-big-bang-produced-equal-amounts-of-matter-and-antimatter.htm |date=19 October 2017 |work=TechTimes.com |access-date=26 October 2017 }}</ref><ref name="NAT-20171020">{{cite journal |author=Smorra C.|display-authors=et al |title=A parts-per-billion measurement of the antiproton magnetic moment |date=20 October 2017 |journal=[[Nature (journal)|Nature]] |volume=550 |issue=7676 |pages=371–374 |doi=10.1038/nature24048 |pmid=29052625 |bibcode=2017Natur.550..371S |s2cid=205260736 |url=https://cds.cern.ch/record/2291601/files/nature24048.pdf |doi-access=free }}</ref> It is consistent with the most precise measurement of the proton magnetic moment (also made by BASE in 2014), which supports the hypothesis of CPT symmetry. This measurement represents the first time that a property of antimatter is known more precisely than the equivalent property in matter.

In January 2022, by comparing the charge-to-mass ratios between antiproton and negatively charged hydrogen ion, the BASE experiment has determined the antiproton's charge-to-mass ratio is identical to the proton's, down to 16 parts per trillion.<ref>{{Cite web|title=BASE breaks new ground in matter–antimatter comparisons|url=http://home.cern/news/news/physics/base-breaks-new-ground-matter-antimatter-comparisons|access-date=2022-01-05|website=CERN|language=en}}</ref><ref>{{Cite journal|last1=Borchert|first1=M. J.|last2=Devlin|first2=J. A.|last3=Erlewein|first3=S. R.|last4=Fleck|first4=M.|last5=Harrington|first5=J. A.|last6=Higuchi|first6=T.|last7=Latacz|first7=B. M.|last8=Voelksen|first8=F.|last9=Wursten|first9=E. J.|last10=Abbass|first10=F.|last11=Bohman|first11=M. A.|date=2022-01-05|title=A 16-parts-per-trillion measurement of the antiproton-to-proton charge–mass ratio|url=https://www.nature.com/articles/s41586-021-04203-w|journal=Nature|volume=601 |issue=7891 |language=en|pages=53–57|doi=10.1038/s41586-021-04203-w|pmid=34987217 |bibcode=2022Natur.601...53B |s2cid=245709321 |issn=1476-4687}}</ref>