  The lepton number violating signal of like-sign-dileptons (LSD), p p \to
\ell^\pm\ell^\pm + 2 jets, is investigated within a model of mixing in the
neutrino sector assuming the existence of heavy Majorana neutrino states with a
left--handed coupling to the light leptons. The LSD signal receives
contributions both from the resonant production of a heavy Majorana neutrino
(N) and from the exchange of a virtual N in the WW fusion mechanisms. These two
possibilities are discussed in detail and compared. Helicity amplitudes are
given pointing out differences with calculations previously reported by other
authors. The signal cross--sections are computed at the energy of the LHC
collider (sqrt{S}=14 TeV) at CERN and within the existing experimental limits
on the mixing couplings, including those coming from neutrinoless double beta
decay. Detailed angular distributions of signal reactions which are
complementary to previous studies on the argument are presented.
