Penguin diagrams in the charm sector in K+ --> pi+ nu anti-nu

Abstract

We evaluate at next-to-next-to-leading order (NNLO) the QCD corrections to the charm contribution from penguin diagrams to the decay K+ --> pi+ nu anti-nu. A NNLO calculation is already available in the literature. We provide an independent check of the results of non-anomalous and anomalous diagrams. We use Renormalization Group improvement and an effective theory framework to resum the large logarithms that appear. In the case of the non-anomalous diagrams, our results for the decoupling coefficients and anomalous dimensions, as well as the final numerical result, are in agreement with those of the previous calculation. In the anomalous case, analytical and numerical disagreements are observed.