THE ISGUR-WISE FUNCTION FROM THE LATTICE

We calculate the Isgur-Wise function by measuring the elastic scatteri ng amplitude of a D meson in the quenched approximation on a 24(3) x 4 8 lattice at beta = 6.2, using an O(a)-improved fermion action. Fittin g the resulting chirally extrapolated Isgur-Wise function to Stech's r elativistic-oscillator parametrization, we obtain a slope parameter rh o2 = 1.2(-3)+7. We then use this result, in conjunction with heavy-qua rk symmetry, to extract V(cb) from the measured BBAR --> DlnuBAR diff erential decay width. We find \V(cb)] square-root tau(B)/(1.48 ps) = 0 .038(-2-3)+2+8, where the first error is due to experimental uncertain ties, while the second is due to the uncertainty in our lattice determ ination of rho2.