  We give a progress report on the calculation of B meson mixing matrix
elements, focusing on contributions that could arise beyond the Standard Model.
The calculation uses asqtad (light quark) and Fermilab (heavy quark) valence
actions and MILC ensembles with 2+1 flavors of asqtad sea quarks. We report
preliminary B^0_s fit results, at a lattice spacing of 0.12 fm, for the SUSY
basis of effective four-quark mixing operators and include an estimate for the
final error budget.
