Effective action approach to calculation of spin potentials in heavy quarkonium

Abstract

We formally derive the spin-orbit and spin-spin potentials in heavy quarkonium from a general effective action. We then specialize to the perturbative effective action for short distances and obtain agreement with the lowest-order Bethe-Salpeter results, including the contact spin-spin interaction which arises in an unusual way in our paper. For large distances, the leading log model is used. Though it is not possible to solve this analytically, some interesting qualitative features are pointed out.