The BPS spectra and superconformal points in massive N = 2 supersymmetric QCD Original Research Article

We present a detailed study of the analytic structure, BPS spectra and superconformal points of the N = 2 susy SU(2) gauge theories with Nf = 1, 2, 3 massive quark hypermultiplets. We compute the curves of marginal stability with the help of the explicit solutions for the low-energy effective actions in terms of standard elliptic functions. We show that only a few of these curves are relevant. As a generic example, the case of Nf = 2 with two equal bare masses is studied in depth. We determine the precise existence domains for each BPS state, and show how they are compatible with the RG flows. At the superconformal point, where two singularities coincide, we prove that (for Nf = 2) the massless spectrum consists of four distinct BPS states and is S-invariant. This is due to the monodromy around the superconformal point being S, providing strong evidence for exact S-duality of the SCFT For all Nf, we compute the slopes ω of the β-functions at the fixed point couplings and show that they are related to the anomalous dimensions α of u = 〈trƒ2〉 by ω = 2(α − 1).