On the strong coupling $N^{(*)}N^{(*)}\pi$

TL;DR

This paper investigates the strong interaction vertices involving nucleons and their excited states with pions using QCD, revealing suppression patterns and comparing results with existing theories and experiments.

Contribution

It provides the first calculation of the strong coupling constants for $N^*N o ext{pi}$ and $N^*N^* o ext{pi}$ vertices using the most general interpolating currents in QCD.

Findings

The $N^*N ext{pi}$ coupling is strongly suppressed.

The $N^*N^* ext{pi}$ coupling is about half of the $NN ext{pi}$ coupling.

Results are consistent with some existing theoretical and experimental data.

Abstract

We study the strong vertices $N^*N\pi$, $N^*N^*\pi$ and $NN\pi$ in QCD, where $N^*$ denotes the negative parity $N (1535)$ state. We use the most general form of the interpolating currents to calculate the corresponding strong coupling constants. It is obtained that the coupling associated to $N^*N\pi$ vertex is strongly suppressed compared to those related to two other vertices. The strong coupling corresponding to $N^*N^*\pi$ is obtained to be roughly half of that of $NN\pi$ vertex. We compare the obtained results on $N^*N\pi$ and $NN\pi$ vertices with the existing predictions of other theoretical studies as well as those extracted from the experimental data.