Heavy Majorana neutrino production at electron-muon colliders

Possibilities for detecting heavy Majorana neutrinos ($N$'s) at future $e{\mu}$ colliders are investigated. In contrast to the $e^-e^+$ colliders (LEP200 and NLC), the center-of-mass (CMS) energies achieved at $e{\mu}$ colliders can be much higher and the $Z$-mediated $s$ channel is excluded automatically. This opens the attractive possibility of having high production cross sections for $N$'s and at the same time probing only the strength of charged current couplings of $N$'s ($NWe$ and $NW{\mu}$). The production cross sections and the expected numbers of events for the reaction $e^{\mp} {\mu}^{\pm} \to NN \to W^{\pm} {\ell}^{\mp} W^{\pm} {\ell}^{\prime \mp}$ are calculated for various masses $M$ of the Majorana neutrinos and for the CMS energies $\sqrt{s} = 0.5-6.0$ TeV. The values of the charged current coupling parameters are set equal to their present upper bounds. We obtain reasonably high production cross sections. Further, the effects of the off-shell intermediate $N$'s turn out to be significant only at $\sqrt{s} \stackrel{>}{\approx} 2$ TeV.