K-meson vector and tensor decay constants and BK-parameter from Nf=2   tmQCD
  We present work in progress on the computation of the K-meson vector and tensor decay constants, as well as the B-parameter in Kaon oscillations. Our simulations are performed in a partially quenched setup, with two dynamical (sea) Wilson quark flavours, having a maximally twisted mass term. Valence quarks are either of the standard or the Osterwalder-Seiler maximally twisted variety. These two regularizations can be suitably combined in order to obtain a BK parameter which is both multiplicatively renormalizable and O(a) improved. 
P. Dimopoulos, R. Frezzotti, V. Gimenez, V. Lubicz, F. Mescia, G.C.   Rossi, S. Simula and A. Vladikas