NNLO QCD corrections to $\mathrm{\Delta }{\mathrm{\Gamma }}_s$ in the $B_s-{\bar{B}}_s$ system

This report summarises recent advances made in the calculation of the NNLO QCD corrections to the width difference $\mathrm{\Delta }{\mathrm{\Gamma }}_s$ in the $B_s-{\bar{B}}_s$ system. The inclusion of the effects due to current-current operators leads to an updated prediction of $\mathrm{\Delta }{\mathrm{\Gamma }}_s=(0.076\pm 0.017){\text{ps}}^{-1}$, which narrows the gap between theory and experiment.