Closed-Form Summation of RG-Accessible Logarithmic Contributions to   Semileptonic B-Decays and Other Perturbative Processes
  For any perturbative series that is known to $k$-subleading orders of perturbation theory, we utilise the process-appropriate renormalization-group (RG) equation in order to obtain all-orders summation of series terms proportional to $\alpha^n \log^{n-k}(\mu^2)$ with $k = {0,1,2,3}$, corresponding to the summation to all orders of the leading and subsequent-three-subleading logarithmic contributions to the full perturbative series. These methods are applied to the perturbative series for semileptonic $b$-decays in both MS-bar and pole-mass schemes, and they result in RG-summed series for the decay rates which exhibit greatly reduced sensitivity to the renormalization scale $\mu$. Such summation via RG-methods of all logarithms accessible from known series terms is also applied to perturbative QCD series for vector- and scalar-current correlation functions, the perturbative static potential function, the (single-doublet standard-model) Higgs decay amplitude into two gluons, as well as the Higgs-mediated high-energy cross-section for $W^+W^-\to ZZ$ scattering. The resulting RG-summed expressions are also found to be much less sensitive to the renormalization scale than the original series for these processes. 
M.R. Ahmady, F.A. Chishtie, V. Elias, A.H. Fariborz, N. Fattahi,   D.G.C. McKeon, T.N. Sherry, T.G.Steele