$\Lambda_b\to\Sigma_c^{(*)}\pi l{\bar\nu}$ in the heavy quark, chiral, and large $N_c$ limits
The decay of $\Lambda_b\to\Sigma_c^{(*)}\pi l{\bar\nu}$ processes are calculated in the framework of heavy baryon chiral perturbation theory with help of the $1/N_c$ expansion. The decay rate distributions over $v\cdot v^{\prime}$ where $v$ and $v^{\prime}$ are the 4-vector velocities of $\Lambda_b$ and $\Sigma_c^{(*)}$ respectively, and over the pion and lepton energies are given. The decay branching ratios amount to about $1.21(0.971)%$ for $\Lambda_b\to\Sigma_c\pi l{\bar\nu}$ and $0.798(0.640)%$ for $\Lambda_b\to\Sigma_c^*\pi l{\bar\nu}$ by using the baryonic Isgur-Wise function predicted by QCD sum rule (large $N_c$ QCD).