Virtual excited neutrino exchange inWboson pair production

Abstract

We discuss the effects of a t-channel excited electron neutrino on the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{W}^{+}{W}^{\ensuremath{-}}.$ Data collected by the OPAL Collaboration at CERN LEP energies up to $189\mathrm{GeV}$ are used to establish $95%$ confidence level bounds on the mass and couplings of this excited neutrino. Rejection limits are also obtained for a future $500\mathrm{GeV}$ Next Linear Collider machine, assuming no excited neutrino will be detected at such an energy regime.