A estrutura do nucleon na QCD e o modelo estatístico a Quarks
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Data
2010-07-29
Autores
Mirez Tarrillo, Carlos Alberto [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Nessa tese, consideramos um modelo estatíıstico a quarks no qual todos os quarks individuais do sistema (quarks do mar e de valência) são confinados por uma interação efetiva central, relativística, com intensidade e expressões iguais para as componentes escalar e vetorial. Consideramos a distribuição de Fermi-Dirac para os quarks nesse modelo, a densidade de probabilidade para um sistema a quarks com níveis de energia e temperatura T, com potenciais químicos apropriados, correspondentes aos quarks leves up (u) e down (d), de modo que as funções de onda do próton e nêutron fiquem corretamente normalizadas. A diferença entre as interações dos quarks u e d é atribuída às contribuições devidas aos instantons, que são dependentes dos spins dos constituintes, e implicam na diferença de massa entre o nucleon (n1/2) e a ressonância 3/2. Os parâmetros do modelo são fixados por dados experimentais disponíveis. O parâmetro de temperatura T é ajustado pelo valor da violação da regra de soma de Gottfried, e os potenciais químicos pela normalização do nucleon, com o correspondente ajuste dos quarks de valência u e d. Para um melhor ajuste do modelo, acrescentamos efeitos devido aos processos da QCD perturbativa de emissão de glúons por quarks, que são divididos em pares quark-antiquark (os quais geram iguais componentes do mar). Consideramos no modelo que os quarks constituintes no nucleon possuem uma sub-estrutura, que por sua vez é extraída, para os quarks e antiquarks, a partir da função de estrutura do píon. Dentro deste modelo estatístico de quarks confinados linearmente obtemos a assimetria de sabores e a correspondente função de estrutura do nucleon. Obtemos a distribuição da razão e a diferençaa de quarks do mar no próton...
In this thesis, we consider a statistical quark model where all individual quarks of the system ( sea and valence quarks) are confined by an effective central interaction with intensity and equal expressions for scalar and vector components. We consider the Fermi-Dirac distribution for quarks in this model, the probability density for a quark system with energy levels and temperature T, with appropriate chemical potentials, related to the light quarks up (u) and down (d), to give the correct neutron and proton normalizations. The difference between the interactions of quarks u and d is supposed to come from instanton contributions, that are spindependent of the constituents, implying in the mass difference of nucleon (n1/2) and 3/2 resonance. The model parameters are determined by the available experimental data. The temperature parameter T is adjusted by the value of the Gottfried sum rule violation, and the chemical potentials by the corresponding normalization of the valence quarks u and d in the nucleon. Moreover, to improve the model, we consider perturbative QCD processes of gluon emissions by the quarks, which split into quark-antiquark pairs (to which generates equal components of the sea). Also, as the quarks in the model are considered as having substructure, such quark and antiquark substructure are extracted from the pion structure function. Within this statistical model of quarks confined linearly we obtain the flavor asymmetry and corresponding structure function of the nucleon. We obtain the ratio and the difference of sea quark distributions in the nucleon, given by ¯ d/¯u, ¯ d-¯u, as well as the ratio and the difference of the structure functions of neutron and proton: Fn 2 /Fp 2 and Fp 2 -Fn 2 , which are compared with the experimental available results. We made an application of the model, calculating the content of strangeness in the sea of the... (Complete abstract click electronic access below)
In this thesis, we consider a statistical quark model where all individual quarks of the system ( sea and valence quarks) are confined by an effective central interaction with intensity and equal expressions for scalar and vector components. We consider the Fermi-Dirac distribution for quarks in this model, the probability density for a quark system with energy levels and temperature T, with appropriate chemical potentials, related to the light quarks up (u) and down (d), to give the correct neutron and proton normalizations. The difference between the interactions of quarks u and d is supposed to come from instanton contributions, that are spindependent of the constituents, implying in the mass difference of nucleon (n1/2) and 3/2 resonance. The model parameters are determined by the available experimental data. The temperature parameter T is adjusted by the value of the Gottfried sum rule violation, and the chemical potentials by the corresponding normalization of the valence quarks u and d in the nucleon. Moreover, to improve the model, we consider perturbative QCD processes of gluon emissions by the quarks, which split into quark-antiquark pairs (to which generates equal components of the sea). Also, as the quarks in the model are considered as having substructure, such quark and antiquark substructure are extracted from the pion structure function. Within this statistical model of quarks confined linearly we obtain the flavor asymmetry and corresponding structure function of the nucleon. We obtain the ratio and the difference of sea quark distributions in the nucleon, given by ¯ d/¯u, ¯ d-¯u, as well as the ratio and the difference of the structure functions of neutron and proton: Fn 2 /Fp 2 and Fp 2 -Fn 2 , which are compared with the experimental available results. We made an application of the model, calculating the content of strangeness in the sea of the... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Fisica nuclear, Quarks, Cromodinamica quantica, Nuclear physics, QCD (Nuclear physics)
Como citar
MIREZ TARRILLO, Carlos Alberto. A estrutura do nucleon na QCD e o modelo estatístico a Quarks. 2010. 188 f. Tese (doutorado) - Universidade Estadual Paulista, Instituto de Física Teórica, 2010.