Chiral behaviour of Delta B = 2 and Delta C =2 matrix elements

We investigate the light-quark mass and spatial volume dependence of matrix elements of Delta B = 2 and Delta C = 2 four-fermion operators. These operators are relevant for Neutral B(s) and D mixing in and beyond the Standard Model. An important conclusion of this work is that the chiral extrapolations for matrix elements of heavy-light meson mixing beyond the Standard Model are more complicated than that for the Standard Model mixing matrix elements.