Kaon-box contribution to the anomalous magnetic moment of the muon

TL;DR

This paper calculates the charged kaon-box contributions to the muon's anomalous magnetic moment using a functional QCD approach, updating previous pion-box results and confirming suppression of box contributions beyond pions.

Contribution

It provides a novel calculation of the kaon-box contribution to the muon g-2 using Dyson-Schwinger and Bethe-Salpeter equations within a dispersive framework.

Findings

Kaon-box contribution: -0.48(2)(4) x 10^{-11}

Pion-box contribution: -15.7(2)(3) x 10^{-11}

Confirms suppression of box contributions beyond pions.

Abstract

We present results for the charged kaon-box contributions to the hadronic light-by-light (HLBL) correction of the muon's anomalous magnetic moment. To this end we determine the kaon electromagnetic form factor within the functional approach to QCD using Dyson-Schwinger and Bethe-Salpeter equations and evaluate the kaon-box contribution as defined in the dispersive approach to HLBL. As an update to previous work we also re-evaluate the charged pion-box contribution taking effects due to isospin breaking into account. Our results are $a_\mu^{\pi^\pm-\text{box}} = -15.7 \,(2)(3) \times 10^{-11}$ and $a_\mu^{K^\pm-\text{box}} = -0.48 \,(2)(4) \times 10^{-11}$ thus confirming the large suppression of box contributions beyond the leading pion box.