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Quenched and first unquenched lattice HQET determination of the Bs-Meson width difference

We present recent results for the prediction of the Bs lifetime difference from lattice Heavy Quark Effective Theory simulations. In order to get a next-to-leading order result we have calculated the matching between QCD and HQET and the two-loop anomalous dimensions in the HQET for all the ΔB=2 operators, in particular for the operators which enter the width difference. We present results from quenched and, for the first time, from unquenched simulations. We obtain for the Bs lifetime difference, (ΔΓ_Bs/Γ_Bs)^{(que.)}=(5.1+/- 1.9+/- 1.7)10^(-2) and (ΔΓ_Bs/Γ_Bs)^{(unq.)}=(4.3+/- 2.0+/- 1.9)10^(-2) from the quenched and unquenched simulations respectively