Pion axioproduction revisited

TL;DR

This paper extends the analysis of pion axioproduction to include the Roper resonance, showing it enhances cross sections across energy ranges and remains stable under certain model parameter variations, unlike the $ riangle$ resonance.

Contribution

It introduces the Roper resonance into the chiral perturbation theory framework for pion axioproduction, analyzing its impact on cross sections and resonance behavior across axion models.

Findings

Roper resonance enhances cross sections within its energy range.

Roper resonance's enhancement remains stable under $ ext{sin}^2{eta}$ variations.

$ riangle$ resonance peaks diminish as $ ext{sin}^2{eta}$ approaches 1.

Abstract

In this work, we extend the analysis of the pion axioproduction, $aN \to \pi{N}$, to include the impact of the Roper resonance $N^*(1440)$ together the previously studied $\Delta(1232)$ resonance. Our theoretical framework is chiral perturbation theory with explicit resonance fields to account for their respective impacts. We find that the Roper resonance also leads to an enhancement of the cross section within its energy range for various axion models. This enhancement provided by the Roper maintains stability even when the parameter $\sin^2{\beta}$ of the DFSZ model undergoes variations. In contrast, the enhancement given by the $\Delta$ gradually diminishes and finally disappears as $\sin^2{\beta}$ approaches $1$. Furthermore, the resonance peaks given by the $\Delta$ are approximately the same in both the KSVZ model and the DFSZ model with $\sin^2{\beta} = \tfrac{1}{2}$, while the resonance peak given by the Roper in the former model is much more pronounced.