Nucleon-charmonium interactions from lattice QCD

TL;DR

This lattice QCD study investigates low-energy interactions between nucleons and charmonium states, revealing attractive forces with long-range tails and providing scattering lengths that differ significantly from experimental assumptions, thus deepening understanding of nonperturbative QCD phenomena.

Contribution

The paper presents the first realistic lattice QCD calculations of nucleon-charmonium interactions near physical pion mass, using the HAL QCD method to extract potentials and scattering parameters.

Findings

Interactions are attractive at all distances.

Long-range tail consistent with two-pion exchange.

Scattering lengths are significantly larger than experimental estimates.

Abstract

We present a realistic lattice QCD study on low-energy $N$-$J/\psi$ and $N$-$\eta_c$ interactions based on (2+1) flavor configurations with nearly physical pion mass $m_\pi=146$ MeV. The interactions, extracted from the spacetime correlations of nucleon and charmonium system by using the HAL QCD method, are found to be attractive in all distances and possess a characteristic long-range tail consistent with the two-pion exchange potential. The resulting $S$-wave scattering lengths are $0.30(2)\left(^{+0}_{-2}\right)$ fm, $0.38(4)\left(^{+0}_{-3}\right)$ fm, and $0.21(2)\left(^{+0}_{-1}\right)$ fm for spin-$3/2$ $N$-$J/\psi$, spin-$1/2$ $N$-$J/\psi$, and spin-$1/2$ $N$-$\eta_c$, respectively. Our results are orders of magnitude larger than those from the photoproduction experiments assuming the vector meson dominance. Our findings may provide deeper understanding of the nonperturbative QCD phenomena ranging from the origin of nucleon mass to the in-medium $J/\psi$ mass modification as well as the properties of hidden-charm pentaquark states.