e-e- collisions mediated by composite neutrinos

The lepton number violating process e(-)e(-) --> W-W- has been widely discussed in connection to the Majorana neutrino exchange mechanism. Here, we discuss this process in a composite neutrino model where excited Majorana neutrinos are exchanged. We find several qualitatively different features from the neutrino exchange case: (1) Longitudinally polarized W bosons are not produced, (2) neutrinoless double beta decay does not strongly constrain and a much larger cross section is expected, and (3) CP violating phases may be explored, because all excited neutrinos are heavy, and therefore large mixings among them are expected.