Observation of B+→(Ξ)over-barc0Λc+ and evidence for B0→(Ξ)over-barc-Λc+

We report the first observation of the decay B+->(Xi) over bar (0)(c)Lambda(+)(c) with a significance of 8.7 sigma and evidence for the decay B-0 ->(Xi) over bar (-)(c)Lambda(+)(c) with a significance of 3.8 sigma. The product B(B+->(Xi) over bar (0)(c)Lambda(+)(c))xB (Xi) over bar (0)(c)->(Xi) over bar (+)pi(-)) is measured to be (4.8(-0.9)(+1.0)+/- 1.1 +/- 1.2)x10(-5), and B(B-0 ->(Xi) over bar (-)(c)Lambda(+)(c))xB ($) over bar (-)(c)->(Xi) over bar (+)pi(-)pi(-)) is measured to be (9.3(-2.8)(+3.7)+/- 1.9 +/- 2.4)x10(-5). The errors are statistical, systematic and the error of the Lambda(+)(c)-> pK(-)pi(+) branching fraction, respectively. The decay B+->(Xi) over bar (0)(c)Lambda(+)(c) is the first example of a two-body exclusive B+ decay into two charmed baryons. The data used for this analysis was accumulated at the Upsilon(4S) resonance, using the Belle detector at the e(+)e(-) asymmetric-energy collider KEKB. The integrated luminosity of the data sample is equal to 357 fb(-1), corresponding to 386x10(6) (B) over bar pairs.