Constituent quarks and the gluonic contribution to the spin of the nucleon [Elektronische Ressource] / submitted by Gamal Eldahoumi

Constituent Quarks and the GluonicContribution to the Spin of the NucleonLudwig-Maximilians-Universität MünchenFaculty of PhysicsThesis submittedByGamal Eldahoumi from Be nghazi/LibyaMunichJanuary 2 009First S upervisor: Prof. Dr . Harald Fri tzschSecond S upervisor: Prof. Dr . Ivo SachsDate of examination: April 29, 2009 ABSTRACTThe internal structure of the nucleon is more complicated than expected in a simple quark model. In particular, the portion of the nucleon spin carried by the spins of the quarks is not, as expected, of the order of one, but according to the experimental data much smaller. In this thesis we study the spin structure of the proton in quantumchromodynamics.The constituent quark model, based on SU(6), predicts that the spin of the proton should be carried by the quarks, in disagreement with the experiments. It appears strange, that the theoretical model works so well for the magnetic moments of the nucleons, but not for the spin, although the spin and the magnetic moments are closely related to each other. We shall resolve this problem by assuming that the constituent quarks have an internal structure on their own. Thus a constituent quark has a dynamical structure, and we can introduce notions like the quark or gluon distributions inside a constituent quark.