The Isgur-Wise Function from the Lattice

We calculate the Isgur-Wise function by measuring the elastic scattering amplitude of a $D$ meson in the quenched approximation on a ${24}^3\times 48$ lattice at $\beta =6.2$, using an $O(a)$-improved fermion action. We use this result, in conjunction with heavy-quark symmetry, to extract $\mathrm{\mid }{V}_{cb}\mathrm{\mid }$ from the experimentally measured $\bar{B}\to D^{\ast }l\bar{\nu }$\ differential decay width.