Sea quark effects in B_K from N_f=2 clover-improved Wilson fermions
  We report calculations of B_K using two flavours of dynamical clover-improved Wilson lattice fermions and look for dependence on the dynamical quark mass at fixed lattice spacing. We see some evidence for dynamical quark effects. In particular B_K decreases as the sea quark masses are reduced towards the up/down quark mass. Our meson masses are quite heavy and a firm prediction of B_K is a task for future simulations. 
J. M. Flynn, F. Mescia, A. S. B. Tariq (for the UKQCD Collaboration)