https://www.ge.infn.it/jlab12/IT/files/0612014-C.F..pdf

Nucleon electromagnetic form factors

We review the application of non-relativistic constituent quark models to study one, two and three non-strange baryon systems. We present results for the baryon spectra, potentials and observables of the nucleon?nucleon (NN), N?, ?? and NN*(1440) systems, and binding energies of three non-strange baryon systems. We emphasize the observable effects related to quark antisymmetry and its interplay with quark dynamics.

https://iopscience.iop.org/article/10.1088/0034-4885/68/5/R01/pdf

Quark-model study of few-baryon systems

Precise proton and neutron form factor measurements at Jefferson Lab, using spin observables, have recently made a significant contribution to the unraveling of the internal structure of the nucleon. Accurate experimental measurements of the nucleon form factors are a test-bed for understanding how the nucleon’s static properties and dynamical behavior emerge from QCD, the theory of the strong interactions between quarks. There has been enormous theoretical progress, since the publication of the Jefferson Lab proton form factor ratio data, aiming at reevaluating the picture of the nucleon. We will review the experimental and theoretical developments in this field and discuss the outlook for the future.

The structure of the nucleon: Elastic electromagnetic form factors

Precise proton and neutron form factor measurements at Jefferson Lab, using spin observables, have recently made a significant contribution to the unraveling of the internal structure of the nucleon. Accurate experimental measurements of the nucleon form factors are a test-bed for understanding how the nucleon's static properties and dynamical behavior emerge from QCD, the theory of the strong interactions between quarks. There has been enormous theoretical progress, since the publication of the Jefferson Lab proton form factor ratio data, aiming at reevaluating the picture of the nucleon. We will review the experimental and theoretical developments in this field and discuss the outlook for the future.

The Structure of the Nucleon: Elastic Electromagnetic Form Factors

We present an unquenched quark model for baryons in which the effects of the quark-antiquark pairs (uū, dđ, and ss) are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechanism. In the present approach, the contribution of the quark-antiquark pairs can be studied for any inital baryon and for any flavor of the qq pairs. It is shown that, while the inclusion of the qq pairs does not affect the baryon magnetic moments, it leads to a sizable contribution of the orbital angular momentum to the spin of the proton and the A hyperon.

Unquenched quark model for baryons: Magnetic moments, spins, and orbital angular momenta

We study the performance of some recent potential models suggested as effective interactions between constituent quarks. In particular, we address constituent quark models for baryons with hybrid $Q\ensuremath{-}Q$ interactions stemming from one-gluon plus meson exchanges. Upon recalculating two of such models we find them to fail in describing the $N$ and $\ensuremath{\Delta}$ spectra. Our calculations are based on accurate solutions of the three-quark systems in both a variational Schr\"odinger and a rigorous Faddeev approach. It is argued that hybrid $Q\ensuremath{-}Q$ interactions with a sizable one-gluon-exchange component encounter difficulties in describing baryon spectra due to the specific contributions from one-gluon and meson exchanges together. In contrast, a chiral constituent quark model with a $Q\ensuremath{-}Q$ interaction relying solely on Goldstone-boson exchange is capable of providing a unified description not only of the $N$ and $\ensuremath{\Delta}$ spectra but also of all strange baryons in good agreement with phenomenology.

L. Glozman

Papers

Effective Q-Q interactions in constituent quark models