A first study of the semi-leptonic decay of the ${\mathrm{\Lambda }}_b$ baryon

We present the preliminary results of the first Lattice study of the baryonic Isgur and Wise function obtained from the matrix element of the weak current between $\mathrm{\Lambda }$-baryon external states. Its dependence on the heavy and light quark masses is studied. Some result on the semi-leptonic decay ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c+l\nu$ are given.