Inclusive Λ_c^+ production in e^+e^- annihilations at √s=10.54  GeV and in Υ(4S) decays

We present measurements of the total production rates and momentum distributions of the charmed baryon Λ_c^+ in e^+e^-→hadrons at a center-of-mass energy of 10.54 GeV and in Υ(4S) decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in e^+e^-→cc[overbar] events, allowing direct studies of c-quark fragmentation. We measure a momentum distribution for Λ_c^+ baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of =0.574±0.009 and a total rate of N_(Λc)^(qq[overbar]) =0.057±0.002(exp)±0.015(BF)  Λ_c^+ per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, pK^-π^+. In Υ(4S) decays we measure a total rate of N_(Λc)^Υ=0.091±0.006(exp)±0.024(BF) per Υ(4S) decay, and find a much softer momentum distribution than expected from B decays into a Λ_c^+ plus an antinucleon and one to three pions.