Measurement of the Branching Fractions of the Decays ${\bar{B}}^0\to {\Lambda }_c^{+}\bar{p}$ and $B^{-}\to {\Lambda }_c^{+}\bar{p}{\pi }^{-}$

Abstract

We present studies of two-body and three-body charmed baryonic B decays in a sample of 232 million $B\bar{B}$ pairs collected with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ storage ring. The branching fractions of the decays ${\bar{B}}^0\to {\Lambda }_c^{+}\bar{p}$ and $B^{-}\to {\Lambda }_c^{+}\bar{p}{\pi }^{-}$ are measured to be $(2.15\pm 0.36\pm 0.13\pm 0.56)\times 10^{-5}$ and $(3.53\pm 0.18\pm 0.31\pm 0.92)\times 10^{-4}$, respectively. The uncertainties quoted are statistical, systematic, and from the ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ branching fraction. We observe a baryon-antibaryon threshold enhancement in the ${\Lambda }_c^{+}\bar{p}$ invariant mass spectrum of the three-body mode and measure the ratio of the branching fractions to be $\mathcal{B}(B^{-}\to {\Lambda }_c^{+}\bar{p}{\pi }^{-})/\mathcal{B}({\bar{B}}^0\to {\Lambda }_c^{+}\bar{p})=16.4\pm 2.9\pm 1.4$. These results are preliminary.

18 pages, 7 postscript figues, submitted to ICHEP2006