2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/38918We present a first test of heavy quark spin-flavour symmetries in matrix elements for semi-leptonic decays \bar B to D l\barνand \bar B to D^* l\barν. We show that O(1/m_Q) corrections are small at masses around the charm for form factors protected by Luke's Theorem, but are of order 30-40 \% for h_V and h_V/h_{A_{1}}.3 pages in uuencoded-compressed-PostScript format, to appear in the Proceedings of LATTICE 93, Dallas, USA; Edinburgh Preprint 93/534High Energy Physics - LatticeHigh Energy Physics - Phenomenologytext