Search for charginos, neutralinos, and gravitinos at LEP

An update of the searches for charginos and neutralinos in DELPHI is presented, based mainly on recent data collected at centre-of-mass energies of 161GeV and 172GeV. No signal is found. For a sneutrino with mass above 300GeV/c^2 and a mass difference between the chargino and the lightest neutralino above 10GeV/c^2 the lower limit at 95% confidence level on the chargino mass ranges from 84.5GeV/c^2 to the kinematical limit (86.0GeV/c^2). The limit in the case of a light sneutrino is 67.8GeV/c^2. Upper limits on neutralino pair production cross-sections of about a picobarn are derived. The (mu,M_2) domain excluded in the MSSM-GUT scenario is determined. For a heavy sneutrino a lower limit on the mass of the lightest neutralino which of 24.9GeV/c^2 for tan(beta) .ge. 1 is derived. The search has been extended to the case where the lightest neutralino is unstable and decays into a photon and a gravitino.