Semileptonic Form Factors - A Model-Independant Approach

We demonstrate that the $B\to D^{(*)}l\nu$ form factors can be accurately predicted given the slope parameter $\rho^2$ of the Isgur-Wise function. Only weak assumptions, consistent with lattice results, on the wavefunction for the light degrees of freedom are required to establish this result. We observe that the QCD and $\frac{1}{m_Q}$ corrections can be systematically represented by an effective Isgur-Wise function of shifted slope. This greatly simplifies the analysis of semileptonic B decay. We also investigate what the available semileptonic data can tell us about lattice QCD and Heavy Quark Effective Theory. A rigorous identity relating the form factor slope difference $\rho_{D^*}^2-\rho_{A_1}^2$ to a combination of form factor intercepts is found. The identity provides a means of checking theoretically evaluated intercepts with experiment.