Multi-instanton calculus in N=2 supersymmetric gauge theory. II. Coupling to matter.

We further discuss the N = 2 superinstantons in SU (2) gauge theory, obtained from the general self-dual solutions of topological charge n constructed by Atiyah, Drinfeld, Hitchin and Manin (ADHM). We realize the N = 2 supersymmetry algebra as actions on the superinstanton moduli. This allows us to recast in concise superfield notation our previously obtained expression for the exact classical interaction between n ADHM superinstantons mediated by the adjoint Higgs bosons, and moreover, to incorporate N F flavors of hypermultiplets. We perform explicit 1-and 2-instanton checks of the Seiberg-Witten prepotentials for all N F and arbitrary hypermultiplet masses. Our results for the low-energy couplings are all in precise agreement with the predictions of Seiberg and Witten except for N F = 4, where we find a finite renormalization of the coupling which is absent in the proposed solution.