## Seminar on Theoretical Nuclear Physics

## 22.05.17 16:15

# Electromagnetic decay of the neutral pion investigated using the Dyson-Schwinger framework

## Esther Weil (Gießen)

In this talk I will summarize our recent calculation of the transition form factor of the neutral pion to two virtual photons (π^{0} → γ^{(∗)}γ^{(∗)}). This form factor is described by a QCD matrix element, so that a non-perturbative approach is required. Our method is to numerically solve truncated versions of the Dyson-Schwinger and Bethe-Salpeter equations. Using this technique we have calculated the form factor in different kinematic regimes. In the first half of my talk I will discuss the case of one on-shell and one highly virtual photon. In this regime our approach predicts a sizable correction to the expected Brodsky-Lepage scaling prediction. In the second half I will discuss the rare decay π^{0} → e^{+}e^{−}. I will focus on a rediscovered numerical method, expected to have applications to other systems, in which the integration contour is routed along a complicated path in the complex plane.

The talk is based on our recent publications arXiv:1704.06046 and arXiv:1704.05774.

(Seminarraum II, HISKP)