Next-to-Leading Order QCD Corrections to Delta F =2 effective Hamiltonians

The most general QCD next-to-leading anomalous-dimension matrix of all possible four-fermion, dimension-six $\Delta F=2$ operators is computed. The results of this calculation can be used in many phenomenological applications, among which the most important are those related to theoretical predictions of $K^0-\bar{K}^0 $ and $B^0-\bar{B}^0$ mixing in several extension of the Standard Model (Supersymmetry, left-right symmetric, multi-Higgs models, etc.), to estimates of the $B^0_s$--$\bar B^0_s$ width difference, $\Delta \Gamma_{B_s}$, and to the calculation of the $O(1/m_b^3)$ corrections for inclusive b-hadron decay rates.