The Determination of $|\Vcb|$ and QCD Sum Rules in Hqet

Abstract

I review recent developments in Heavy Quark Effective Theory (HQET) that lead to an almost model--independent determination of the $|\Vcb|$ element of the Cabibbo--Kobayashi--Maskawa matrix from exclusive semileptonic $B\ra D^{(*)}$ decays. In particular, I compare the theoretical uncertainties in the $B\ra D^*\ell\,\bar\nu$ and the $B\ra D\,\ell\,\bar\nu$ decay modes. I discuss the applications of QCD sum rules within HQET to semileptonic heavy meson decays and give predictions for the form factors measurable in $B\ra D^{(*)}\ell\,\bar\nu$ decays.