Neutral-pion decay into an electron-positron pair: A review and update

TL;DR

This paper reviews the current understanding of the rare neutral pion decay into an electron-positron pair, focusing on radiative corrections, updated data, and implications for recent experimental results and Standard Model tests.

Contribution

It provides an updated review of theoretical and experimental aspects of the $c0^0 o e^+e^-$ decay, including radiative corrections and the connection to Dalitz decay, in light of recent measurements.

Findings

Updated decay rate numbers and radiative correction details.

Analysis of the discrepancy between Standard Model predictions and experimental results.

Discussion of implications of new measurements by NA62 and previous KTeV results.

Abstract

This work aims to review several aspects of the current status of the rare $\pi^0\to e^+e^-$ decay. A particular emphasis is made on radiative corrections and detailed interpretation of related quantities, some numbers appearing in the literature are updated, and the connection with the Dalitz decay, $\pi^0\to e^+e^-\gamma$, is discussed. This comes timely as it is aligned with an announcement of a preliminary result of a new branching-ratio measurement done by the NA62 Collaboration, which brings new light into an earlier-reported discrepancy between the Standard Model prediction and the (until-recently latest) precise KTeV result.