Measurement of ${\sigma }_{{\Lambda }_b^0}/{\sigma }_{{\overline{B}}^0}\times \mathcal{B}({\Lambda }_b^0\to {\Lambda }_c^{+}{\pi }^{-})/\mathcal{B}({\overline{B}}^0\to D^{+}{\pi }^{-})$ in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

We present the first observation of the baryon decay ${\Lambda }_b^0\to {\Lambda }_c^{+}{\pi }^{-}$ followed by ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ in $106{\mathrm{pb}}^{-1}$ $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ in the CDF experiment. In order to reduce systematic error, the measured rate for ${\Lambda }_b^0$ decay is normalized to the kinematically similar meson decay ${\overline{B}}^0\to D^{+}{\pi }^{-}$ followed by $D^{+}\to {\pi }^{+}{K}^{-}{\pi }^{+}$. We report the ratio of production cross sections ($\sigma$) times the ratio of branching fractions ($\mathcal{B}$) for the momentum region integrated above $p_T>6\mathrm{GeV}/c$ and pseudorapidity range $|\eta |<1.3$: $\sigma (p\overline{p}\to {\Lambda }_b^{0}X)/\sigma (p\overline{p}\to {\overline{B}}^{0}X)\times \mathcal{B}({\Lambda }_b^0\to {\Lambda }_c^{+}{\pi }^{-})/\mathcal{B}({\overline{B}}^0\to D^{+}{\pi }^{-})=0.82\pm 0.08(\mathrm{stat})\pm 0.11(\mathrm{syst})\pm 0.22[\mathcal{B}({\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+})]$.

Figure 1

${\Lambda }_b^0\to {\Lambda }_c^{+}{\pi }^{-}$ yield with binned likelihood mass fit. The background shapes are defined in the text.

Figure 2

${\overline{B}}^0\to D^{+}{\pi }^{-}$ yield with binned likelihood fit. The background shapes are defined in the text.