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

TL;DR

This paper independently verifies NNLO QCD corrections to charm penguin diagrams in the K+ --> pi+ nu anti-nu decay, confirming previous results for non-anomalous diagrams and highlighting discrepancies in anomalous cases.

Contribution

Provides an independent NNLO calculation and verification of QCD corrections for charm penguin diagrams in rare kaon decay, using effective theory and renormalization group techniques.

Findings

Agreement with previous results for non-anomalous diagrams

Discrepancies found in anomalous diagram calculations

Enhanced understanding of QCD effects in rare kaon decays

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.