Measurement of the Lifetimes of the Charmed Positive D, Positive F Mesons and Positive Lambda(c) Charmed Baryon.

An experiment was performed in the 350 GeV wide -band neutrino beam at the Fermi National Accelerator Laboratory using a high-precision, high-efficiency hybrid emulsion/neutrino spectrometer, with which the mean lifetimes of the D('+), D('0) and F('+) mesons and (LAMDA)(,c)('+) baryon were measured. 1829 neutrino interactions were reconstructed with a vertex within the emulsion fiducial volume, 1242 of which were subsequently found in the emulsion. In 49 of the found neutrino events a charmed particle, produced at the primary vertex was observed to decay within the emulsion volume. The mean lifetimes of charmed particles were determined from the reconstructed decays of 5 D('+), 15 D('0), 3 F('+) mesons: and 8 (LAMDA)(,c)('+) baryons:. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). The charmed particle masses measured in this experiment were:. M(,D('+)) = 1851 (+OR-) 20 MeV/c('2). M(,D('0)) = 1856 (+OR-) 15 MeV/c('2). M(,F('+)) = 2042 (+OR-) 33 MeV/c('2). M(,(LAMDA)(,c)('+)) = 2265 (+OR-) 30 MeV/c('2). A candidate event for the production and decay of a long-lived neutral charmed baryon was observed, with a decay mode, mass and lifetime of. Decay Mode Mass (MeV/c('2)) Decay Time (x10(' -13) sec). NB (--->) p(pi)('-)K(,s)('0) 2450 (+OR-) 15 77.2 (+OR-) 0.9. or. NB (--->) pK('-)K(,s)('0) 2647 (+OR-) 11 83.4 (+OR-) 0.9. The probability of this event being due to background nuclear interactions is less than 3.1 x 10('-4) events.