Superheavy Majorana neutrinos effect in the lepton-number violating e-+e-→μ-+μ- process

In the minimal extension of the standard electroweak theory with ultra massive Majorana neutrinos, the process e(-) + e(-) --> mu (-) + mu (-) could be observable, in sharp contrast with the reaction e(-) + e(-) --> W- + W- which is entirely controlled by neutrinoless double beta decay beta beta (0 nu) data. Our result provides the process background that must be confronted "new physics" models which postulate doubly charged particles, such as the gauge bilepton Y-- in the SU(3)(c) x SU(3)(L) x U(1) model, the left-right SU(2)(L) x SU(2)(R) x U(1)(B-L) one, and its supersymmetric version with doubly charged Higgs multiplets. (C) 2000 Elsevier Science B.V. All rights reserved.