Nuclear Physics B61 (1973) 102-115. North-Holland Publishing Company - PRODUCTION IN K-p INTERACTIONS Aachen-Berlin-CERN-London-Vienna Collaboration M. DEUTSCHMANN lIl. PhysikalischesInstitut der TechnischenHochschule, Aachen H.H. KAUFMANN lnstttut )~r Hochenergiephysik der Akademie der Wissenschaftender DDR, Berlin-Zeuthen T. BESLIU*, G. KELLNER, D.J. KOCHER**, D.R.O. MORRISON, A. OLOFSSON, H. WAHL and K.L. WERNHARD** CERN, European Organization for Nuclear Research, Geneva M.J. COUNIHAN*** Imperial College, London M. MARKYTAN lnstitut ~ Hochenergiephysik der Osterreichischen Akademie do" Wissenschaflen, Vienna Received 18 June 1973 Abstract: We report on 20 events of ~ - production observed in K-p interactions at 10 GeV/c. A summary of the present world sample is given and new averagevalues of the mass and lifetime of the FL- are calculated. Production and decay characteristics are discussed. I. Introduction Interactions with at least two visible strange particle decays have been studied in a 10 GeV/c K-p experiment, using pictures taken in the 1.5 m British and 2 m CER~ hydrogen bubble chambers exposed at the CERN P.S. About 200 000 photographs from the 1.5 m chamber and 450 000 photographs from the 2 m chamber have been scanned and measured yielding a total of about 240 000 events of all topologies. Approximately 13 000 were events with at least two visible strange particle decays. About 60% of these 2V events have been fully analyzed so far, and we have found a total of 20 ~2- events. In this paper we report on 13 new [2- events, the results concerning seven event.~ * Now at University of Bucarest. ** Now at Universitit Inmbruck, Austria. *** Now at CERN.