Extracting the chiral anomaly from gamma pi --> pi pi

TL;DR

This paper develops dispersive methods to analyze the gamma pi --> pi pi process, aiming to extract the chiral anomaly from experimental data, which is crucial for understanding the muon's anomalous magnetic moment.

Contribution

It introduces dispersive representations incorporating pi pi phase shifts to accurately extract the chiral anomaly from cross-section data up to 1 GeV.

Findings

Dispersive framework effectively relates cross-section data to the chiral anomaly.

Highlights the importance of precise gamma pi --> pi pi amplitude modeling.

Provides insights for reducing uncertainties in muon g-2 calculations.

Abstract

We derive dispersive representations for the anomalous process gamma pi --> pi pi with the pi pi P-wave phase shift as input. We investigate how in this framework the chiral anomaly can be extracted from a cross-section measurement using all data up to 1 GeV, and discuss the importance of a precise representation of the gamma pi --> pi pi amplitude for the hadronic light-by-light contribution to the anomalous magnetic moment of the muon.