R – Parity Violating Signals for Chargino Production at LEP II

We study chargino pair production at LEP II in supersymmetric models with spontaneously broken R–parity. We perform signal and background analyses, showing that a large region of the parameter space of these models can be probed through chargino searches at LEP II. In particular, we determine the attainable limits on the chargino mass as a function of the magnitude of the effective bilinear R–parity violation parameter ǫ, demonstrating that LEP II is able to unravel the existence of charginos with masses almost up to its kinematical limit even in the case of R–parity violation. This requires the study of several final state topologies since the usual MSSM chargino signature is recovered as ǫ → 0. Moreover, for sufficiently large ǫ values, for which the chargino decay mode χ → τJ dominates, we find through a dedicated Monte Carlo analysis that the χ mass bounds are again very close to the kinematic limit. Our results establish the robustness of the chargino mass limit, in the sense that it is basically model-independent. They also show E-mail [email protected] E-mail [email protected] E-mail [email protected] E-mail [email protected] that LEP II can establish the existence of spontaneous R–parity violation in a large region of parameter space should charginos be produced.