  We investigate the possibility of detecting Majorana neutrinos at the Large
Hadron-electron Collider (LHeC), an electron-proton collision mode at CERN. We
study the $l_j^{+} + 3 jets$ ($l_j\equiv e ,\mu ,\tau$) final states which are,
due to leptonic number violation, a clear signature for intermediate Majorana
neutrino contributions. Such signals are not possible if the heavy neutrinos
have Dirac nature. The interactions between Majorana neutrinos and the Standard
Model (SM) particles are obtained from an effective lagrangian approach. We
present our results for the total cross section as a function of the neutrino
mass, the effective couplings and the new physics scale. We also show the
discovery region as a function of the Majorana neutrino mass and the effective
couplings. Our results show that the LHeC may be able to discover Majorana
neutrinos with masses lower than $700$ GeV and $1300$ GeV for electron beams
settings of $E_e=50$ GeV and $E_e=150$ GeV, respectively.
