Search for spontaneous R-parity violation at root s=183 GeV and 189 GeV

Searches for spontaneous $ R$- parityviolating signals at $\sqrt{s}=183$\,GeV and \mbox{$\sqrt{s}=189$\,GeV} have been performed using 1997 and 1998 DELPHIdata, under the assumption of $ R$- paritybreaking in the third lepton family. The expected topology for the decay of a pair of charginosinto two acoplanartaus plus missing energywas investigated and no evidence for a signal was found. The results were used to derive a limit on the charginomass and to constrain the allowed domains of the MSSM parameter sp.