Combined study of gamma p to eta p and pi-p to eta n in a chiral constituent quark approach

TL;DR

This study uses a chiral constituent quark model to analyze eta-meson production in gamma p and pi- p reactions, successfully matching experimental data and exploring the roles of known and potential new resonances.

Contribution

The paper applies a chiral constituent quark approach to simultaneously analyze gamma p to eta p and pi- p to eta n reactions, identifying dominant resonances and investigating new resonance contributions.

Findings

Successful reproduction of differential cross sections and asymmetries up to 2 GeV

Identification of key resonances like S11(1535) and D13(1520)

No evidence found for missing resonances in the studied reactions

Abstract

Within a chiral constituent quark model approach, $\eta$-meson production on the proton {\it via} electromagnetic and hadron probes are studied. With few parameters, differential cross-section and polarized beam asymmetry for \gamma p \to \eta p$ and differential cross section for $\pi^- p\to \eta n$ processes are calculated and successfully compared with the data in the center-of-mass energy range from threshold up to 2 GeV. The five known resonances $S_{11}(1535)$, $S_{11}(1650)$, $P_{13}(1720)$, $D_{13}(1520)$, and $F_{15}(1680)$ are found to be dominant in the reaction mechanisms in both channels. Possible roles plaied by new resonances are also investigated and in the photoproduction channel, significant contribution from $S_{11}$- and $D_{15}$-resonances, with masses around 1715 MeV and 2090 MeV, respectively, are deduced. For the so-called missing resonances, no evidence is found within the investigated reactions. The helicity amplitudes and decay widths of $N^* \to \pi N, \eta N$ are also presented, and found consistent with the PDG values.