The role of the N*(1535) resonance and the pi^- p --> KY amplitudes in the OZI forbidden pi N --> phi N reaction

TL;DR

This paper investigates the pi N --> phi N reaction near threshold using a chiral unitary approach, highlighting the role of the N*(1535) resonance and demonstrating the importance of coupled-channel effects for accurate cross section predictions.

Contribution

It introduces a combined analysis of multiple reactions and assesses the N*(1535) resonance's coupling to phi N, providing insights into OZI suppression mechanisms.

Findings

Good agreement with experimental cross sections when constraining KLambda amplitudes.

Moderate coupling of N*(1535) to phi N due to cancellation effects.

N*(1535) pole approximation underestimates the cross section.

Abstract

We study the pi N --> phi N reaction close to the phi N threshold within the chiral unitary approach, by combining the pi^- p --> K^+ Sigma^-, pi^- p --> K^0 Sigma^0 and pi^- p --> K^0 Lambda amplitudes with the coupling of the phi to the K components of the final states of these reactions via quantum loops. We obtain a good agreement with experiment when the dominant pi^- p --> K^0 Lambda amplitude is constrained with its experimental cross section. We also evaluate the coupling of the N*(1535) to phi N and find a moderate coupling as a consequence of partial cancellation of the large KY components of the N*(1535). We also show that the N*(1535) pole approximation is too small to reproduce the measured cross section for the pi N --> phi N reaction.