  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.
