Non-perturbative scale evolution of four-fermion operators in   two-flavour QCD
  We apply finite-size recursion techniques based on the Schrodinger functional formalism to determine the renormalization group running of four-fermion operators which appear in the Delta S=2 effective weak Hamiltonian of the Standard Model. Our calculations are done using O(a) improved Wilson fermions with N_f=2 dynamical flavours. Preliminary results are presented for the four-fermion operator which determines the B_K parameter in tmQCD. 
ALPHA Collaboration: P. Dimopoulos, G. Herdoiza, F. Palombi, C. Pena,   S. Sint, A. Vladikas