Vafa-Witten Theory on N=2 and N=4 Twisted Superspace in Four Dimensions
  We construct a new off-shell twisted hypermultiplet with a scalar and an anti-self-dual tensor superfields. Using the N=2 twisted superspace formalism, we construct a Donaldson-Witten theory coupled to the hypermultiplet. We show that this action possesses the Vafa-Witten type N=4 twisted supersymmetry at the on-shell level. We also reconstruct the action using a N=4 twisted superconnection formalism. 
Junji Kato, Akiko Miyake