W-exchange contributions in hadronic decays of bottom baryon ${\mathrm{\Lambda }}_b$

The nonleptonic decays ${\mathrm{\Lambda }}_b\to {\mathrm{\Sigma }}_c^{\ast -}{\pi }^{+},{\mathrm{\Xi }}_c^{\ast 0}{K}^0$ and ${\mathrm{\Lambda }}_b\to {\mathrm{\Delta }}^0{D}^0,{\mathrm{\Sigma }}^{\ast -}{D}_0^{+}$ are studied. In addition, the decays ${\mathrm{\Lambda }}_b\to {\mathrm{\Xi }}_c^0{K}^0,{\mathrm{\Sigma }}^{-}{D}_s^{+}$ are analyzed. For all these decays the dominant contribution comes from $W-$exchange, and for the decay ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c^{+}{\pi }^{-}$, in addition to factorization, baryon pole contribution to the $p$-wave (parity conserving) decay amplitude $B$ is discussed.