DeltaGamma Non-perturbative parameter sum rules

The mixing of $B_{s/d}$ and $\overline{B}_{s/d}$ mesons constitutes a FCNC 
process and is therefore very sensitive to new physics effects and has the 
potential to severely constrain models that could explain the current flavour 
anomalies. We present SM predictions for the mixing observables based on a 
sum rule determination of the required hadronic matrix elements of the full 
basis of dimension-six operators, which is a competitive alternative to 
lattice simulations. Results for the effects of a non-zero strange-quark 
mass in $B_s$ mixing are shown for the first time. The reliability of the 
heavy-quark expansion and sum rule results is demonstrated by considering 
lifetime ratios of $B$ and $D$ mesons where we find very good agreement 
with the experimental averages.