Lifetime difference in Bs mixing: Standard Model and beyond

We present a calculation of 1/mb2 corrections to the lifetime differences of Bs mesons ΔΓBs in the heavy-quark expansion. We find that they are small to significantly affect ΔΓBs and present the result for lifetime difference including non-perturbative 1/mb and 1/mb2 corrections. We also analyze the generic ΔB=1 New Physics contributions to ΔΓBs and provide several examples.