  We present an update of the Fermilab-MILC Collaboration's calculation of
hadronic matrix elements for B^0-\bar{B^0} mixing. This work is a more extended
analysis than our recent publication of the SU(3)-breaking ratio xi
[arXiv:1205.7013]. We use the asqtad staggered action for light valence quarks
in combination with the Fermilab interpretation of the Sheikoleslami-Wohlert
action for heavy quarks. The calculations use MILC's 2+1 flavor asqtad
ensembles. Ensembles include four lattice spacings from approximately 0.125 fm
to 0.045 fm and up/down to strange quark mass ratios as low as 0.05. Our
calculation covers the complete set of five operators needed to describe B
mixing in the Standard Model and beyond. In addition to an update including a
fuller set of analyzed data, we comment on the form of the staggered ChPT
extrapolation function.
