We report final results for the $D^{\pm }$, $F^{\pm }$, and $\Lambda _c^{}{}_{}{}^{+}$ lifetimes measured with a hybrid emulsion spectrometer in the wide-band neutrino beam at Fermilab. In total, 3886 neutrino and antineutrino interactions were located in the fiducial volume of the emulsion. From these interactions we have unambiguously identified $6 F^{\pm }$ and $13 \Lambda _c^{}{}_{}{}^{+}$ decays, for which the fitted lifetimes are $\tau \left(F^{\pm }\right)=\left({2.6}_{-0.9\mathrm{}}^{+1.6\mathrm{}}\right)\times {10}^{-13\mathrm{}}$ s and $\tau \left(\Lambda _c^{}{}_{}{}^{+}\right)=\left({2.0}_{-0.5\mathrm{}}^{+0.7\mathrm{}}\right)\times {10}^{-13\mathrm{}}$ s. 28 other decays are consistent with a $D^{+}$ or $D^{-}$ hypothesis. From these events, we obtain a $D^{\pm }$ lifetime of (${11.1}_{-2.9\mathrm{}}^{+4.4\mathrm{}}$) × ${10}^{-13\mathrm{}}$s.

• Received 13 December 1985

DOI:https://doi.org/10.1103/PhysRevLett.56.1767