A QCD Relation Between Hyperfine Splittings in Isospin doublets - A Light Quark Symmetry?

Abstract

Recent data on the $D^*$ masses confirm the QCD prediction based on the \REF{\ICHJL}{Isaac Cohen and Harry J. Lipkin, \plb{84}{323}{1979}} very general assumption $\({\ICHJL}\)$ that the spin-dependence of the quark couplings to photons and gluons have the same structure and differ only in the value of the coupling constants, This prediction with no free parameters and using the $\Xi$ and $\Xi^*$ masses as input follows from noting that the charmed antiquark $\bar c$ and the strange diquark (ss) have exactly the same couplings to both the photon (Q=-2/3) and to the gluon (both are color antitriplets). New predictions are obtained with this approach. Corrections to the naive model are investigated and shown to be small.