Extraction of characteristic constants in QCD with perturbative and nonperturbative methods

Abstract

Part I is devoted to the extraction of the QCD coupling from a bound state approach at low energy scales, where unphysical singularities make the RG-improved pQCD useless. Theoretical results on the meson spectrum based on a Bethe-Salpeter formalism adjusted for QCD have been exploited for the determination of experimental values of α_s below 1GeV by comparison with the data. Results quantitatively confirm the recently developed Analytic Perturbation Theory approach to IR phenomena down to 200 MeV. Below this scale the extracted values give a hint about the vanishing of the QCD coupling as Q^2 goes to zero. In part II the possibility of inferring the spin-dependent gluon distribution from scaling violations is addressed by performing a NLO analysis of inclusive DIS data in pQCD. In addition, this work presents a phenomenological study of open-charm photoproduction in the polarized case, which is tailored to the COMPASS experiment in view of upcoming data. It is shown that current inclusive data allow a reliable determination of the gluon first moment, whereas the x-shape is significantly affected by the assumed functional form. On the other hand, studies of charm pseudo-data reveal that the open-charm approach should be capable to reduce the bias induced by the choice of input densities, and to pin down the x-shape of the gluon polarization.

Ph.D. Thesis (Advisor: S.Forte). PartI: On the QCD coupling at low energy scales. PartII: Progress in the determination of the gluon polarization

References in corpus (39)

• The COMPASS Experiment at CERN
• Models for the Polarized Parton Distributions of the Nucleon
• Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio sigma(L)/sigma(T)
• The theory and phenomenology of polarized deep inelastic scattering
• Precise determination of the spin structure function ${\mathbf{g}}_1$ of the proton, deuteron and neutron
• Measurement of the Neutron Spin Structure Function $g_1^n$ with a Polarized ^3He Target
• The Deuteron Spin-dependent Structure Function g1d and its First Moment
• Next-to-Leading Order Radiative Parton Model Analysis of Polarized Deep Inelastic Scattering
• Polarized Parton Distributions in the Nucleon
• Measurement of the Proton Spin Structure Function g1p with a Pure Hydrogen Target
• Improving the Weizsäcker-Williams Approximation in Electron-Proton Collisions
• Next-to-leading order QCD corrections to high-p_T pion production in longitudinally polarized pp collisions
• Neural Network Parametrization of Deep-Inelastic Structure Functions
• Precision Measurement of the Neutron Spin Asymmetries and Spin-dependent Structure Functions in the Valence Quark Region
• Determination of the Bjorken Sum and Strong Coupling from Polarized Structure Functions
• Measurement of the Spin Asymmetry in the Photoproduction of Pairs of High-pT Hadrons at HERMES
• Gluon polarization in the nucleon from quasi-real photoproduction of high-pT hadron pairs
• Measurement of the $x$- and $Q^2$-Dependence of the Asymmetry $A_1$ on the Nucleon
• Heavy-Quark Production
• Determination of polarized parton distribution functions and their uncertainties
• MRST partons generated in a fixed-flavour scheme
• Theory of hard photoproduction
• Single-Inclusive Jet Production in Polarized pp Collisions at O(alpha_s^3)
• Longitudinal Polarized Parton Densities Updated
• Impact of CLAS and COMPASS data on Polarized Parton Densities and Higher Twist
• Measurement of the Neutron Spin Structure Function g2n and Asymmetry A2n
• Measurement of the Proton Spin Structure Function $g_1(x,Q^2)$ for $Q^2$ from 0.15 to 1.6 GeV${}^2$ with CLAS
• Next-to-leading order QCD corrections to one hadron-production in polarized pp collisions at RHIC
• Spin asymmetry A_1^d and the spin-dependent structure function g_1^d of the deuteron at low values of x and Q^2
• Leading and higher twists in the proton polarized structure function at large Bjorken x
• SU(3) Breaking Effects in Hyperon Semi-Leptonic Decays and the extraction of F and D
• Gluon polarization from correlated high-pT hadron pairs in polarized electro-production
• Photoproduction of Heavy Quarks in Next-to-Leading Order QCD with Longitudinally Polarized Initial States
• Improved Measurement of Double Helicity Asymmetry in Inclusive Midrapidity pi^0 Production for Polarized p+p Collisions at sqrt(s)=200 GeV
• Longitudinally Polarized Photoproduction of Inclusive Hadrons Beyond the Leading Order
• Determination of Delta G/G from Open Charm events at COMPASS
• Hadron-Pair Photoproduction in Longitudinally Polarized Lepton-Nucleon Collisions
• Photoproduction of Hadron Pairs at Fixed-Target Experiments
• Polarized Structure Functions: Theory and Phenomenology

Cited by in corpus (2)

• Unbiased Polarised Parton Distribution Functions and their Uncertainties
• The Bjorken sum rule with Monte Carlo and Neural Network techniques