Two-loop QCD penguin contribution to the width difference in $B_s-{\bar{B}}_s$ mixing

Marvin Gerlach, Ulrich Nierste, Vladyslav Shtabovenko +1

We consider two-loop QCD corrections to the element ${\Gamma }_{12}^q$ of the decay matrix in $B_q-{\bar{B}}_q$ mixing, $q=d,s$, in the leading power of the Heavy Quark Expansion. The calcul…