This work concerns two topics in QCD. Part I is devoted to the extraction of the strong coupling at lowenergy scales, where unphysical singularities make the RG-improved pQCD useless. In the present work, theoretical results on the meson spectrum based on a Bethe-Salpeter formalism adjusted for QCD have been exploited to extract experimental values for the QCD coupling below 1~GeV by comparison with the data. Results quantitatively confirm the recently developed Analytic Perturbation Theory approach to IR phenomena down to 200 MeV. Furthermore, below this scale the extracted values give a hint about the vanishing of the QCD coupling in agreement with results from lattice simulations.PartII investigates the nucleon spin structure, i.e. polarized pdfs.The possibility of inferring the gluon polarization from scaling violations has been studied by performing a NLO analysis in pQCD of world data from inclusive DIS. In addition, a phenomenological study of the open-charm photoproduction at COMPASS (CERN) has been performed.Results show that current DIS data only allow a better determination of the gluon first moment and leave the x-shape fairly undetermined. Pseudo-data analyses have revealed, on the other hand, that the open-charm approach is capable to strongly reduce the bias induced by the assumed functional form of input densities, and to pin down the x-shape of the gluon polarization.
|Titolo:||Extraction of characteristic constants in QCD with perturbative and nonperturbative methods|
|Supervisori e coordinatori interni:||BELLINI, GIANPAOLO|
|Data di pubblicazione:||2008|
|Settore Scientifico Disciplinare:||Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici|
Settore FIS/04 - Fisica Nucleare e Subnucleare
|Citazione:||Extraction of characteristic constants in QCD with perturbative and nonperturbative methods ; tutor : S. Forte ; coordinatore : G. Bellini. - Milano : Università degli studi di Milano. FACOLTA' DI SCIENZE MATEMATICHE, FISICHE E NATURALI, 2008. ((20. ciclo, Anno Accademico 2006/2007.|
|Appare nelle tipologie:||13 - Tesi di dottorato discussa entro ottobre 2010|