Understanding nucleon radii with potential models
A new paper by Jinfeng Lao (Indiana U., co-PI) and his student Daniel Gallimore (Indiana U.) presents a detailed study of the charge and mass distributions within a nucleon (both proton and neutron included) and the associated squared radii based on a potential model approach. We find 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. This important feature allows for a substantial difference between the charge radius and the mass radius. Furthermore, a simultaneous description of the radii of both the proton and neutron could provide valuable constraints on the quark structures of the nucleon, particularly concerning flavor-sensitive correlations such as diquark clustering. These findings offer useful insights for understanding recent GlueX and $J/\psi\text{-}007$ measurements at JLab. Finally, we use simulations to demonstrate a considerable sensitivity of the eccentricities in the initial conditions of heavy ion collisions to the input nucleon profiles, particularly regarding the corresponding overall size characterized by the mass radius.