Two-loop QED radiative corrections to the decay pi0 -> e+ e- : The virtual corrections and soft-photon bremsstrahlung

TL;DR

This paper presents a detailed calculation of two-loop QED radiative corrections to the pi0 -> e+ e- decay, including virtual corrections and soft-photon bremsstrahlung, revealing significant differences from previous approximations in relevant experimental regions.

Contribution

The authors perform an exact two-loop calculation of QED corrections to pi0 decay, including all relevant diagrams and a detailed treatment of divergences, improving upon prior approximate methods.

Findings

Exact two-loop corrections differ significantly from previous approximations.

The calculation provides a closed-form analytic expression for the O(alpha^3 p^2) contribution.

Results impact the interpretation of experimental data like the KTeV measurement.

Abstract

This paper is devoted to the two-loop QED radiative corrections to the decay pi0 -> e+ e-. We compute the virtual corrections without using any approximation and we take into account all the relevant graphs with the inclusion of those omitted in the previous approximative calculations. The bremsstrahlung is then treated within the soft photon approximation. We concentrate on the technical aspects of the calculation and discuss in detail the UV renormalization and the treatment of IR divergences within the dimensional regularization. As a result we obtain the O(alpha^3 p^2) contribution in closed analytic form. We compare the exact two-loop results with existing approximative calculations of QED corrections and find significant disagreement in the kinematical region relevant for the KTeV experiment.