Search for SUSY with R-parity violating $LL\overline{E}$ couplings at $\sqrt{s}$=189 GeV

Searches for pair production of supersymmetric particlesunder the assumption that $R$--parity is not conserved are presented,based on data recorded by the DELPHI detector in 1998from e$^{+}$e$^{-}$ collisions at a centre-of-mass energy of189~GeV. Only one $R$--parity violating $\rm{LL} \bar{\rm E}$term (i.e. one $\lambda$ coupling), which couples\mbox{scalar} leptons to leptons,is considered to be dominant at a time.Moreover, it is assumed that the strength of the $R$--parityviolating couplings is such that the lifetimes can be neglected.The search for pair production of neutralinos, charginos and sleptonshas been performed for both direct $R$--parity violating decaysand indirect cascade decays.The results are in agreement with Standard Model expectations, andare used to update the constraints on the MSSM parametervalues and the mass limits previously derived at \mbox{$\sqrt{s}$~=~183~GeV.}\\The present 95\% C.L. limits on supersymmetric particle masses are:\begin{malist}\item $m_{\tilde{\chi}^0}>~$30~\GeVcc\ and $m_{\tilde{\chi}^\pm}>$~94~\GeVcc;\item $m_{\tilde{\nu}}>$~76.5~\GeVcc \ (direct and indirect decays);\item $m_{\tilde{\ell}_R}>$~83~\GeVcc\ (indirect decay only).\end{malist}