Hyperfine interactions as clues to the structure of elementary particles

The history of hyperfine interactions in hadron physics is reviewed. The recent treatment of hyperfine splittings in meson spectroscopy by Frank and O'Donnell is generalized and applied to baryons as well as mesons by the use of techniques developed for treating hyperfine interactions in atomic physics. New relations between meson and baryon mass splittings are obtained following from the assumption that mesons and baryons are made of the same quarks and have the same color hyperfine interactions at the quark level, with corrections due to color factors and differences between baryon and meson wave functions. Work supported by the U.S. Department of Energy, Division of High Energy Physics, Contract W-31-109-ENG-38 and by the Minerva Foundation, Munich, Germany. 1985–86 Argonne Fellow on leave from the Wiezmann Institute of Science, Rehovot, Israel.