Pion axioproduction revisited

In this work, we extend the analysis of the pion axioproduction, a N →π N , to include the impact of the Roper resonance N^*(1440 ) together with the previously studied Δ (1232 ) resonance. Our theoretical framework is a chiral Lagrangian approach with explicit resonance fields to account for their respective impacts. We find that the N^*(1440 ) also leads to an enhancement of the cross section within its energy range for various axion models. This enhancement given by the N^*(1440 ) maintains stability even when the parameter sin²β of the Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) model undergoes variations. In contrast, the enhancement given by the Δ (1232 ) gradually diminishes and finally disappears as sin²β approaches 1. Furthermore, the resonance peaks given by the Δ (1232 ) are approximately the same in both the Kim-Shifman-Vainstein-Zakharov (KSVZ) model and the DFSZ model with sin²β =1/2 , while the resonance peak given by the N^*(1440 ) in the former model is much more pronounced.