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Published January 2007 | Published
Journal Article Open

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.

Additional Information

© 2007 The American Physical Society. Received 5 September 2006; published 9 January 2007. We are grateful for the extraordinary contributions of our PEP-II colleagues in achieving the excellent luminosity and machine conditions that have made this work possible. The success of this project also relies critically on the expertise and dedication of the computing organizations that support BABAR. The collaborating institutions wish to thank SLAC for its support and the kind hospitality extended to them. This work is supported by the U.S. Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), Institute of High Energy Physics (China), the Commissariat à l'Energie Atomique and Institut National de Physique Nucléaire et de Physique des Particules (France), the Bundesministerium für Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Science and Technology of the Russian Federation, Ministerio de Educación y Ciencia (Spain), and the Particle Physics and Astronomy Research Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A. P. Sloan Foundation.

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