Heavy majorana neutrinos in dilepton production at lepton-proton colliders

Deep inelastic cross sections have been calculated for uniquely charged leptons pair production processes $e^+p\to \bar{\nu}_e\ell^+\ell'^+X$ and $\nu_ep\to e\ell^+\ell'^+X$ $(\ell, \ell' = e, \mu, \tau)$, caused by the exchange of heavy Majorana neutrinos. Possibilities of observation of these processes at the existing HERA ep-collider and at a designed supercollider VLHC have been discussed.