Lifetime of charmed hadrons produced in neutrino interactions

Examples of the decay of charmed hadrons produced by high-energy neutrinos in an emulsion hybrid experiment (WA17, CERN) and in a bubble chamber exposure (E546, Fermilab) have been directly observed. The decay paths of the five charmed candidates found in experiment WA17 (three positively charged and two neutral range from about 50 to 900 mu m, giving charmed hadron proper decay times well consistent with the meanlife expected from current theoretical models ( approximately 5*10/sup -13/s). One of the events represents the production of a Lambda /sub c//sup +/ baryon which decays after (7.3+or-0.1)*10/sup -13/ s to a pK/sup -/ pi /sup +/ final state. The identification of the final state is made possible by the combined information from the emulsion and the associated bubble chamber photo (BEBC). In experiment E546 two neutral and one charged short decays have been detected in the FNAL 15' bubble chamber, in addition to one of undetermined charge. Two of them are interpretable as D/sup 0/ to e /sup +/K/sup -/ nu /sub e/ and D/sup +/ to e/sup +/K/sup -/ pi /sup +/ nu /sub e/ decays, yielding decay times consistent with those of the five events found in experiment WA17. The status of another emulsion hybrid experiment at Fermilab (E553) is also briefly reported. (10 refs).