Relativistic Constituent Quark Model for Baryons

TL;DR

This paper develops a relativistic constituent quark model to calculate baryon electroweak properties, incorporating various extensions and providing insights into baryon structure, form factors, and weak decay parameters.

Contribution

It introduces a comprehensive relativistic quark model with extensions like form factors and wave function mixing, improving understanding of baryon properties and weak interactions.

Findings

Calculated nucleon and hyperon form factors and magnetic moments.

Determined the CKM matrix element V_{us} from baryon data.

Proposed a symmetry breaking scheme consistent with experimental results.

Abstract

The electroweak properties of nucleons and hyperons are calculated in a relativistic constituent quark model. The baryons are treated as three quark bound states, and the diagrams of perturbation theory are considered on the light front. The electroweak properties of the baryons are of nonperturbative nature and can be represented by one-loop diagrams. We consider different extensions of the simplest model: quark form factors, configuration mixing of the wave function, asymmetric wave function, wave function different from the one of a harmonic oscillator valid up to energies of more than 30 GeV$^2$. A comprehensive study of various baryonic properties is given: elastic form factors of the nucleon, magnetic moments of the baryon octet, semileptonic weak form factors. This analysis also gives the Kobayashi-Maskawa matrix element $V_{us}$ and a sound symmetry breaking scheme for the Cabibbo theory. A consistent physical picture appears in this work. The nucleon consists of an unmixed, symmetric three quark state, the wave function of the hyperons is however asymmetric with a spin-isospin-0 diquark. Only for the strangeness-changing weak decay do we need nontrivial form factors.