Charged Kaon production in 3-prong tau decays in DELPHI

The production of charged kaons in the three-prong decay of the tau is studied using the data collected in the DELPHI detector during the LEP-1 data taking between, 1992 and 1995. Algorithms for the reconstruction of the 7 decay vertex and the charged kaon identification in the Barrel RICH are presented. With these tools we tag tau /sup -/ to K/sup -/K/sup +/ tau /sup -/ nu /sub tau / and tau /sup -/K/sup -/ pi /sup +/ pi /sup -/ nu /sub tau / decays on an event-by-event basis. Preliminary results for the inclusive branching ratios tau /sup -/ to K/sup -/K/sup +/ pi /sup -/ nu /sub tau / and tau /sup -/ to K/sup -/ pi /sup +/ pi /sup -/ nu /sub tau /, determined from the 1994 data sample are presented. (5 refs).