Deciphering the mechanism of $J/\psi$-nucleon scattering

TL;DR

This paper investigates the low-energy $J/ar{\psi}$-nucleon scattering, revealing that soft-gluon exchange dominates over coupled-channel mechanisms, which has implications for understanding pentaquark states and gluon roles in nucleons.

Contribution

It provides a comparative analysis of two scattering mechanisms, highlighting the dominance of soft-gluon exchange in $J/\psi N$ interactions.

Findings

Soft-gluon exchange mechanism yields a much larger scattering length.

Coupled-channel mechanism contributes minimally to the scattering length.

Results can be tested via lattice QCD calculations.

Abstract

The low-energy $J/\psi N$ scattering is important for various reasons: it is related to the hidden-charm $P_c$ pentaquark states, provides insights into the role of gluons in nucleon structures, and is relevant to the $J/\psi$ properties in nuclear medium. The scattering can happen through two distinct mechanisms: the coupled-channel mechanism via open-charm meson-baryon intermediate states, and the soft-gluon exchange mechanism. We investigate the $J/\psi N$ $S$-wave scattering length through both mechanisms, and find that the soft-gluon exchange mechanism leads to a scattering length at least one order of magnitude larger than that from the coupled-channel mechanism and thus is the predominant one. The findings can be verified by lattice calculations and will enhance our understanding of the scattering processes breaking the Okubo-Zweig-Iizuka rule.