A Potential Model Study of the Nucleon's Charge and Mass Radius

TL;DR

This study uses a potential model to analyze the charge and mass distributions within nucleons, revealing distinct influences on radii from quark dynamics and nonperturbative QCD effects, with implications for heavy ion collision simulations.

Contribution

It introduces a comparative analysis of different nucleon configurations and highlights the impact of mass radius variations on collision initial conditions.

Findings

Charge radius primarily determined by quark dynamics.

Mass radius significantly affected by nonperturbative QCD contributions.

Nucleon profile variations notably influence collision eccentricities.

Abstract

We study the charge and mass distributions within a nucleon and compute the associated squared radii based on a potential model approach. Different constituent quark configurations such as $\Delta$, $Y$, and quark-diquark are considered and compared, with model parameters calibrated by experimental measurements of the proton and neutron charge radius. The results suggest that while the charge radius is dictated by quark dynamics, the mass radius is strongly influenced by nonperturbative QCD contributions to a nucleon's mass that are not sensitive to the constituent quarks. As a result, the mass radius could become substantially different from the charge radius. The obtained nucleon mass distributions of different configurations are further used for simulations of the initial conditions in heavy ion collisions. The computed eccentricities $\varepsilon_2$ and $\varepsilon_3$ are found to demonstrate a considerable sensitivity to the input nucleon profiles, especially to the mass radius in the peripheral region as well as for systems with fewer participants.