Can neutrino mixings arise from the charged lepton sector?

The neutrino mixing matrix U is in general of the form U = Ue(dagger)U(v), where U-e arises from the diagonalization of charged leptons and Up is from the neutrino sector. We discuss the possibility that U-e is nearly diagonal (in the Lagrangian basis) and the observed mixing arises with good accuracy from U-e. We find that the fact that, in addition to the nearly maximal atmospheric mixing angle theta(23), the solar angle theta(12) is definitely also large while at the same time the third mixing angle theta(13) is small, makes the construction of a natural model of this sort considerably more complicated. We present an example of a natural model of this class. We also find that the case that U-v is exactly of the bimixing type is severely constrained by the bound on theta(13) but not excluded. We show that planned experimental searches for theta(13) could have a strong impact on bimixing models. (C) 2004 Elsevier B.V. All rights reserved.