The π−p→a0−ηp reaction in an effective Lagrangian model

Abstract

In this work, we perform a study of the ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{a}_{0}^{\ensuremath{-}}\ensuremath{\eta}p$ reaction within an effective Lagrangian approach and isobar model. In our model, we consider the excitation of the ${N}^{*}$ and ${\mathrm{\ensuremath{\Delta}}}^{*}$ resonances in the intermediate states and background terms. Based on our model, it is found that this reaction is dominated by the production of the $N(1535)$ in the near threshold region. And the contributions from other well-established ${N}^{*}$ or ${\mathrm{\ensuremath{\Delta}}}^{*}$ resonances only play minor roles. Besides, we discuss the possibility of verifying the existence of a narrow nucleon resonance $N(1685)$/$N(1700)$ proposed by some recent works in the present reaction. With adopting different quantum numbers, we find that it may contribute significantly in this reaction. Thus this reaction may provide a good platform to study the properties of nucleon resonances, e.g., $N(1535)$ and $N(1685)$/$N(1700)$, which couple strongly with the $\ensuremath{\eta}N$ channel. To compare with future experiments, the predictions of the total cross sections, the angular distributions, and invariant mass spectrums of final particles are also presented. Furthermore, the off-shell effects due to high-spin states are also discussed.