Production of supersymmetric particles in elasticepcollisions

The reactions ep{→}pe ̃ \~{}{}Z̃ \~ᵢ and ep{→}p{ν} ̃ \~{}{}W̃ \~_- are investigated, where Z̃ \~ᵢ and W̃ \~_- are a generic neutralino and the lightest chargino eigenstate, respectively. We present both exact results and a modified effective-photon approximation. We show that ten fully measured e ̃ \~{}{}Z̃ \~₁ events with e ̃ \~{}{}{→}eZ̃ \~₁ decay, where the Z̃ \~₁ escape detection, are enough to determine mₑ ̃ \~{}{} and mZ{ ̃ \~{}{}}₁with statistical errors of 2 GeV; the detection of the outgoing proton in a forward proton spectrometer is crucial. e ̃ \~Z{ ̃ \~{}{}}₂and ν ̃ \~W{ ̃ \~{}{}}_{{{-}}}$ production, resulting mostly in final states with one or three charged leptons plus missing ${p}T$, are also discussed. Within the framework of minimal supergravity models, these elastic processes make the DESY ep collider HERA competitive with or even superior to the contemporary colliders CERN LEP I and Fermilab Tevatron as far as searches for supersymmetry are concerned.