  We compute the chiral logarithmic corrections to the Bd and Bs mixing
amplitudes in the Standard Model and beyond. We then investigate the impact of
the inclusion of the lowest-lying scalar heavy-light states to the decay
constants and bag-parameters and show that this does not modify the pion chiral
logarithms, but it does produce corrections which are competitive in size with
the K- and eta-meson chiral logarithms. This conclusion is highly relevant to
the lattice studies since the pion chiral logarithms represent the most
important effect in guiding the chiral extrapolations of the lattice data for
these quantities. Also important is to stress that the pion chiral logarithmic
corrections are useful in guiding those extrapolations as long as Mpi << Delta,
where Delta is the mass gap between the scalar and pseudoscalar heavy-light
mesons.
