Electromagnetic Form Factors of Hyperons in a Relativistic Quark Model

Abstract

The relativistically covariant constituent quark model developed by the Bonn group is used to compute the EM form factors of strange baryons. We present form-factor results for the ground-state and some excited hyperons. The computed magnetic moments agree well with the experimental values and the magnetic form factors follow a dipole Q 2 dependence. 1. Motivation The photo- and electroproduction of mesons from the nucleon is a process in which both electromagnetic and strong interactions occur. One particularly interesting process is the electroproduction of kaons, where a strange quark/antiquark pair is produced from the QCD vacuum. Data from Jefferson Lab have recently been published 1 , but an appropriate theoretical description using isobar models is still lacking. One of the main uncertainties in these models is the incompleteness or absence of any knowledge about the form factors, strong or electromagnetic, of the nucleon and hyperon resonances. This work focusses on the latter. We have used the constituent quark (CQ) model developed by the Bonn group to calculate the electromagnetic form factors of ground-state hyperons and the helicity amplitudes of hyperon resonances. The Bonn CQ model is Lorentz covariant and is therefore well suited to describe baryon properties up to high Q 2 , which involve large recoil eects 2 .