Production of supersymmetric particles in elastic ep collisions.

Abstract

The reactions ep\ensuremath{\rightarrow}pe\ifmmode \tilde{}\else \~{}\fi{}Z${\ifmmode \tilde{}\else \~{}\fi{}}_{i}$ and ep\ensuremath{\rightarrow}p\ensuremath{\nu}\ifmmode \tilde{}\else \~{}\fi{}W${\ifmmode \tilde{}\else \~{}\fi{}}_{\mathrm{\ensuremath{-}}}$ are investigated, where Z${\ifmmode \tilde{}\else \~{}\fi{}}_{i}$ and W${\ifmmode \tilde{}\else \~{}\fi{}}_{\mathrm{\ensuremath{-}}}$ 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\ifmmode \tilde{}\else \~{}\fi{}Z${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$ events with e\ifmmode \tilde{}\else \~{}\fi{}\ensuremath{\rightarrow}eZ${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$ decay, where the Z${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$ escape detection, are enough to determine ${m}_{e}$\ifmmode \tilde{}\else \~{}\fi{} and ${m}_{Z}$${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$ with statistical errors of 2 GeV; the detection of the outgoing proton in a forward proton spectrometer is crucial. e\ifmmode \tilde{}\else \~{}\fi{}Z${\ifmmode \tilde{}\else \~{}\fi{}}_{2}$ and \ensuremath{\nu}\ifmmode \tilde{}\else \~{}\fi{}W${\ifmmode \tilde{}\else \~{}\fi{}}_{\mathrm{\ensuremath{-}}}$ 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.