Evidence item

The article explains that antiproton structure enters the hyperfine frequency at roughly 40 ppm. DIRECT_TEXT

Authenticity UNVERIFIED · extraction UNVERIFIED · independence group none (unreviewed) · created seq 21994

Source: Four ppm measurement of the antihydrogen ground-state hyperfine splitting · locator {} · excerpt hash sha256:9d7d331c7cfe72e2ddd04f90a47dd4c85e3b5284977f485678fc2f74b6e80cad

The hyperfine splitting frequency is a particularly sensitive probe of the internal structure of the antiproton through the Zemach correction and nuclear polarizability at the level of 40 parts per million (ppm).