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

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.

Comments: 10 pages, 5 figures, 2 tables; v2: version accepted for publication in PRD, minor text improvements