A note on Wilson-'t Hooft operators

We find the basic ingredients required to compute the Operator Product Expansion of Wilson-'t Hooft operators in N=4 super-Yang-Mills theory with gauge group G=PSU(3). These include the geometry of certain moduli spaces of BPS configurations in the presence of 't Hooft operators and vector bundles over them. The bundles arise in computing the OPE due to electric degrees of freedom in dyonic operators. We verify our results by reproducing the OPE of 't Hooft operators predicted by S-duality.