Heavy Majorana neutrino production at electron-muon colliders

Possibilities for detecting heavy Majorana neutrinos (Nʹs) at future eμ colliders are investigated. In contrast to the e−e+ colliders (LEP200 and NLC), the center-of-mass (CMS) energies achieved at eμ 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 Nʹs and at the same time probing only the strength of charged current couplings of Nʹs (NWe and NWμ). The production cross sections and the expected numbers of events for the reaction e∓μ±→NN→W±ℓ∓W±ℓ′∓ are calculated for various masses M of the Majorana neutrinos and for the CMS energies 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 Nʹs turn out to be large and they increase with increasing s.