Measurement of σΛb0/ σB̄0×B(Λb0→Λc+π-)/B(B̄0→D+π- ) in pp̄ Collisions at s=1.96TeV

We present the first observation of the baryon decay ${\ensuremath{\Lambda}}_{b}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ followed by ${\ensuremath{\Lambda}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ in $106\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ $p\overline{p}$ collisions at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ in the CDF experiment. In order to reduce systematic error, the measured rate for ${\ensuremath{\Lambda}}_{b}^{0}$ decay is normalized to the kinematically similar meson decay ${\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ followed by ${D}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$. We report the ratio of production cross sections ($\ensuremath{\sigma}$) times the ratio of branching fractions ($\mathcal{B}$) for the momentum region integrated above ${p}_{T}g6\text{ }\text{ }\mathrm{GeV}/c$ and pseudorapidity range $|\ensuremath{\eta}|l1.3$: $\ensuremath{\sigma}(p\overline{p}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{b}^{0}X)/\ensuremath{\sigma}(p\overline{p}\ensuremath{\rightarrow}{\overline{B}}^{0}X)\ifmmode\times\else\texttimes\fi{}\mathcal{B}({\ensuremath{\Lambda}}_{b}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})/\mathcal{B}({\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})=0.82\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.08(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.11(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.22[\mathcal{B}({\ensuremath{\Lambda}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})]$.