Testing nonunitarity of neutrino mixing matrices at neutrino factories

In this paper we explore the effect of nonunitary neutrino mixing on neutrino oscillation probabilities both in vacuum and matter. In particular, we consider the nu(mu)->nu(tau) channel and, using a neutrino factory as the source for nu(mu)'s, discuss the constraints that can be obtained on the moduli and phases of the parameters characterizing the violation of unitarity. We point out how the new CP violation phases present in the case where the nonunitary mixings give rise to spurious degenerate solutions in the parameter space. We also discuss how the true solutions can be extricated by combining measurements at several baselines.