Low-Energy Effective Action of N=2 Gauge Multiplet Induced by   Hypermultiplet Matter
  We study one-loop effective action of hypermultiplet theory coupled to external N=2 vector multiplet. We formulate this theory in N=1 superspace and develop a general approach to constructing derivative expansion of the effective action based on an operator symbol technique adopted to N=1 supersymmetric field models. The approach under consideration allows to investigate on a unique ground a general structure of effective action and obtain both N=2 superconformal invariant (non-holomorphic) corrections and anomaly (holomorphic) corrections. The leading low-energy contributions to effective action are found in explicit form. 
A.T. Banin, I.L. Buchbinder, N.G. Pletnev