Aspects of Non-perturbative QCD FOR Meson Physics

Aspects of Non-perturbative QCD FOR Meson Physics

Bibliographic Details
Main Author: Nguyen, Trang Thi
Language:English
Published: Kent State University / OhioLINK 2010
Subjects:
Nuclear Physics
Non-perturbative QCD
Dyson-Schwinger equations
Meson physics
valence quark distributions in pion and kaon
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=kent1267371699
id ndltd-OhioLink-oai-etd.ohiolink.edu-kent1267371699
record_format oai_dc
collection NDLTD
language English
sources NDLTD
topic Nuclear Physics
Non-perturbative QCD
Dyson-Schwinger equations
Meson physics
valence quark distributions in pion and kaon
spellingShingle Nuclear Physics
Non-perturbative QCD
Dyson-Schwinger equations
Meson physics
valence quark distributions in pion and kaon
Nguyen, Trang Thi
Aspects of Non-perturbative QCD FOR Meson Physics
author Nguyen, Trang Thi
author_facet Nguyen, Trang Thi
author_sort Nguyen, Trang Thi
title Aspects of Non-perturbative QCD FOR Meson Physics
title_short Aspects of Non-perturbative QCD FOR Meson Physics
title_full Aspects of Non-perturbative QCD FOR Meson Physics
title_fullStr Aspects of Non-perturbative QCD FOR Meson Physics
title_full_unstemmed Aspects of Non-perturbative QCD FOR Meson Physics
title_sort aspects of non-perturbative qcd for meson physics
publisher Kent State University / OhioLINK
publishDate 2010
url http://rave.ohiolink.edu/etdc/view?acc_num=kent1267371699
work_keys_str_mv AT nguyentrangthi aspectsofnonperturbativeqcdformesonphysics
_version_ 1719422582532341760
spelling ndltd-OhioLink-oai-etd.ohiolink.edu-kent12673716992021-08-03T05:37:07Z Aspects of Non-perturbative QCD FOR Meson Physics Nguyen, Trang Thi Nuclear Physics Non-perturbative QCD Dyson-Schwinger equations Meson physics valence quark distributions in pion and kaon <p>Quantum Chromodynamics (QCD) is the field theory governing the strong interactions of hadrons. At high energies, due to asymptoticfreedom, perturbation theory is applicable, whereas at low energiesrelevant for hadronic bound states (strong QCD), non-perturbativetechniques are required. One of these techniques, the field-theoretical approach of the Dyson-Schwinger Equations (DSEs), is utilized in the present study.</p><p>Mesons are the simplest hadrons, and thus are an excellent“laboratory” to investigate strong QCD. In particular the propertiesof the pion, the lightest pseudoscalar meson, is determined bynon-perturbative effects such as dynamical chiral symmetry breaking(DCSB). In order to gain a deeper understanding of strong QCD, we investigate two rather different aspects of non-perturbative dynamics formeson physics in this work.</p><p>The first aspect deals with the transition between the perturbativeand non-perturbative regimes of QCD, in particular the determinationof the distance scale for the onset of non-perturbative dynamics. Correlation functions (correlators) with meson quantum numbers,which are vacuum expectationvalues of products of gauge-invariant local operators, are ideally suited for this type of investigation.We consider the vector and axial-vector correlators built from vector and axial-vector currents respectively. We investigate the difference (V-A correlator), sum (V+A correlator), and ratio of the difference and sum of these correlators. In the chiral (massless) limit,to any finite order of perturbation theory, the vector andaxial-vector correlators are identical. Thus the way the difference (V-A) correlator increasesas momentum decreases is a measure of the onset of non-perturbativedynamics. It can provide information on the associated distance scaleand the four quark condensate. The V+A correlator remains close to free-field behavior for distances as large as 1 fm. We therefore usethe ratio of the V-A and V+A correlators as a probe. The requisitenon-perturbative inputs to the calculation are DSE solution for thedressed quark propagator and an Ansatz for the vector and axial vectorvertices.</p><p>The extracted four-quark condensate is compared to results from other models and to theprediction of the vacuum saturation Ansatz. Using Fourier transforms, we calculate the distance scale relevant to the onset of dynamical chiral symmetry breaking and, by implication, of non-perturbative dynamics. Our results are compared to results from QCD sum rule calculations, lattice QCD, and instanton physics.</p><p>The second aspect involves the evaluation of the valence quark distributions in the light pseudoscalar mesons: pions and kaons.Quark distributions in hadrons are intrinsically non-perturbative and thus are currently determined from structure functions measured experimentally in processes like the deep inelastic hadron-lepton scattering and the Drell-Yan lepton-pair production. These distributions give the probability densities of finding a quark carrying a fraction x of the parent hadron's momentum, at a resolving scale Q. We work in the Bjorken limit (very large Q) and concentrate on the valence quark for which the so-called“handbag” diagram mechanism is considered sufficient. Non-perturbative inputs such as the dressed quark propagators and the bound state wave function are taken from DSE solution andBethe-Salpeter solution respectively. The valence quark distributionsin the pion and kaon are compared to available data. This is the first time that bound state descriptions of the quality provided by theBethe-Salpeter solutions have been compared to the quark distributionsmeasured in deep inelastic scattering. </p><p>Using the leading order DGLAP evolution equation for the nonsinglet structure function to evolve to relevantexperimental scales, we compare our results with existing FermiLab data onthe pion at Q = 4.05 GeV, the recent reanalysis of data at Q =5.2 GeV, and an earlier theoretical model which is a primitiveversion of the current model. We also compare the ratio of the kaon to pion distributionswith the Drell-Yan experimental data that produced suchinformation. Approximations used in the formulation are critically evaluated and discussed.</p> 2010-03-11 English text Kent State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=kent1267371699 http://rave.ohiolink.edu/etdc/view?acc_num=kent1267371699 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

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