Paper detail

Numerical updates of lifetimes and mixing parameters of B mesons

We update the Standard-Model predictions for several quantities related to $B_s - \bar B_s$ and $B_d - \bar B_d$ mixing. The mass and width differences in the $B_s$ system read $ ΔM_s^{\rm SM} = (17.3 \pm 2.6) ps^{-1}$ and $ΔΓ_s^{\rm SM}= (0.087 \pm 0.021) ps^{-1}$, respectively. The CP asymmetries in flavour-specific decays are $a_{\rm fs}^{s,\rm SM} = (1.9 \pm 0.3) \cdot 10^{-5}$ and $a_{\rm fs}^{d,\rm SM} = - (4.1 \pm 0.6) \cdot 10^{-4}$. We further critically discuss the sensitivity of $ΔΓ_d$ to new physics and the uncertainties in the relation between $ΔΓ_s$ and the branching fraction of $B_s \to D_s^{(*)}{}^+ D_s^{(*)}{}^-$. Then we present a numerical update of the average width $Γ_s$ in the $B_s$ system and correlate $Γ_s$ with the $B^+$-$B_d$ lifetime ratio. Finally we summarise the key results of our recent global analysis with the CKMfitter collaboration addressing new physics in $B - \bar B$-mixing. In an appropriately defined scenario parametrising new physics in $B - \bar B$-mixing by two complex parameters $Δ_d$ and $Δ_s$ the Standard-Model point {$Δ_d=Δ_s=1$} is disfavoured by 3.6 standard deviations.