  I calculate, at one loop in staggered chiral perturbation theory, the matrix
elements of the complete set of five local operators that may contribute to B
mixing both in the Standard Model and in beyond-the-Standard-Model theories.
Lattice computations of these matrix elements by the Fermilab Lattice/MILC
collaborations (and earlier by the HPQCD collaboration) convert a light
staggered quark into a naive quark, and construct the relevant 4-quark
operators as local products of two local bilinears, each involving the naive
light quark and the heavy quark. This particular representation of the
operators turns out to be important in the chiral calculation, and it results
in the presence of "wrong-spin" operators, whose contributions however vanish
in the continuum limit. If the matrix elements of all five operators are
computed on the lattice, then no additional low energy constants are required
to describe wrong-spin chiral effects.
