The Isgur-Wise function from the lattice

Abstract

We calculate the Isgur-Wise function by measuring the elastic scattering amplitude of a D meson in the quenched approximation on a 24(3) x 48 lattice at beta = 6.2, using an O(a)-improved fermion action. Fitting the resulting chirally extrapolated Isgur-Wise function to Stech's relativistic-oscillator parametrization, we obtain a slope parameter rho2 = 1.2(-3)+7. We then use this result, in conjunction with heavy-quark symmetry, to extract V(cb) from the measured BBAR --> D*lnuBAR differential 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 uncertainties, while the second is due to the uncertainty in our lattice determination of rho2.