A discrete symmetry group for maximal atmospheric neutrino mixing

We propose a discrete non-abelian symmetry group which enforces maximal atmospheric neutrino mixing, while theta(13) = 0 and the solar mixing angle theta(12) remains undetermined; without finetuning, theta(12) will be large but non-maximal. Our extension of the Standard Model has three right-handed neutrino singlets upsilon(R) and implements the seesaw mechanism. Furthermore, we have an enlarged scalar sector with three Higgs doublets and two scalar gauge singlets; the latter have masses and vacuum expectation values of the order of the seesaw scale. Lepton mixing stems exclusively from the upsilon(R) Majorana mass matrix, where non-diagonal elements are generated by the vacuum expectation values of the scalar singlets. The model predicts a neutrino mass spectrum with m(3) > m(2) > m(1), and the effective Majorana mass of neutrinoless betabeta decay is equal to m(1)/m(2)/m(3). (C) 2003 Elsevier B.V. All rights reserved.