Impact of the Delta (1232) resonance on neutral pion photoproduction in chiral perturbation theory

TL;DR

This paper discusses the significance of the Delta (1232) resonance in neutral pion photoproduction, emphasizing the need to include it in chiral perturbation theory to match high-precision experimental data.

Contribution

It evaluates the role of the Delta (1232) resonance and D-waves in improving theoretical descriptions of neutral pion photoproduction within Heavy Baryon Chiral Perturbation Theory.

Findings

High-precision data from MAMI supports including the Delta resonance.

Beyond 170 MeV, additional degrees of freedom are necessary for accurate modeling.

Inclusion of the Delta resonance improves agreement with experimental results.

Abstract

We present an ongoing project to assess the importance of D-waves and the $\Delta (1232)$ resonance for descriptions of neutral pion photoproduction in Heavy Baryon Chiral Perturbation Theory. This research has been motivated by data published by the A2 and CB-TAPS collaborations at MAMI [1]. This data has reached unprecedented levels of accuracy from threshold through to the $\Delta$ resonance. Accompanying the experimental work, there has also been a series of publications studying the theory that show that, to go beyond an energy of $E_\gamma=170$ MeV, it is necessary to include other aspects, in particular the $\Delta (1232)$ as a degree of freedom [2] and possibly higher partial waves [3].