Observation of the decay (B)over-bar(0) -> Lambda(+)(c)(p)over-bar pi(0)

In a sample of 467×106 BB⎯⎯⎯ pairs collected with the BABAR detector at the PEP-II collider at SLAC we have observed the decay B⎯⎯⎯0→Λ+cp⎯⎯π0 and measured the branching fraction to be (1.94±0.17±0.14±0.50)×10−4, where the uncertainties are statistical, systematic, and the uncertainty on the Λ+c→pK−π+ branching fraction, respectively. We determine an upper limit of 1.5×10−6 at 90% C.L. for the product branching fraction ℬ(B⎯⎯⎯0→Σ+c(2455)p⎯⎯)×ℬ(Λ+c→pK−π+). Furthermore, we observe an enhancement at the threshold of the invariant mass of the baryon-antibaryon pair.