Matrix elements of four-fermion operators in the HQET

The B-(B) over bar mixing, B-meson lifetimes, the B-s-(B) over bar(s) lifetime difference and SUSY FCNC effects in Delta B = 2 processes are very important measurable quantities in B-meson phenomenology whose theoretical predictions depend on unknown matrix elements of several four-fermion operators. We present preliminary results for the matrix elements of the relevant four-fermion operators computed on a sample of 600 lattices of size 24(3) x 40 at beta = 6.0, using the SW-Clover action for light quarks with rotated light quark propagators and the lattice version of the HQET for heavy quarks. As a necessary ingredient of the calculation, we also present results for the next-to-leading order matching of the full theory to the lattice HQET (one-and two-loop anomalous dimensions, one-loop QCD-HQET matching coefficients and one-loop continuum-lattice HQET matching coefficients).