Fixing the parameters of Lattice HQET including 1/mB terms

(for the ALPHA collaboration) The study of the CKM matrix elements with increasing precision requires a reliable evaluation of hadronic matrix elements of axial and vector currents which can be done with Lattice QCD. The tiniest entry, |Vub|, can be estimated independently from B → τν and B → pilν decays. The ALPHA collaboration has undertaken the effort to evaluate non-perturbatively the decay constant fB and the f+(q) form factor for q2 close to q2max entering these determinations. Since for the b quark mb a−1 for available lattice sizes, an effective description of the b quark is necessary. HQET provides an example of the latter. As any effective theory, HQET is predictive only when a set of parameters have been determined through a process called matching. The non-perturbative matching procedure applied by the ALPHA collaboration consists of 19 matching conditions needed to fix all the relevant parameters at order 1/mB of the HQET action and the axial and vector currents. We present a study of one-loop corrections to two representative matching conditions. Our results enable us to quantify the quality of the observables used in the matching procedure