Observation and Study of the Baryonic B-Meson Decays B→D^{(*)}pp̅ (π)(π)

We present results for B-meson decay modes involving a charm meson, protons, and pions using 455×10⁶ BB̄ pairs recorded by the BaBar detector at the SLAC PEP-II asymmetric-energy e⁺e⁻ collider. The branching fractions are measured for the following ten decays: B̅⁰→D⁰pp̄, B̅⁰→D⁰pp̄, B̅⁰→D⁺pp̄π⁻, B̅⁰→D⁺pp̄π⁻, B⁻→D⁰pp̄π⁻, B⁻→D⁰ pp̄π⁻, B̅⁰→D⁰pp̄→D0pp̄π⁻π⁺, B̅⁰→D⁰pp̄π⁻π⁺, B⁻→D⁺pp̅π⁻, B⁻→D⁰pp̄π⁻, B⁻→D⁰pp̄π⁻, B̅⁰→D⁰pp̄π⁻π⁺, B̅⁰→D⁰pp̄π⁻π⁺, B⁻→D⁺pp̄π⁻π⁻, and B⁻→D⁺pp̄π⁻π⁻. The four B⁻ and the two five-body B̅⁰ modes are observed for the first time. The four-body modes are enhanced compared to the three- and the five-body modes. In the three-body modes, the M(pp̄) and M(D^{(*)⁰}p) invariant-mass distributions show enhancements near threshold values. In the four-body mode B̅⁰→D⁺pp̄π⁻, the M(pπ⁻) distribution shows a narrow structure of unknown origin near 1.5 GeV/c². The distributions for the five-body modes, in contrast to the others, are similar to the expectations from uniform phase-space predictions.