We study a model for inclusive central particle production in pp and pp reactions based on parton model concepts and lowest-order QCD. In this picture, two-gluon fusion creates a heavy excited state (fireball) whose decay (described by statistical considerations) leads to the creation of light hadrons with low transverse momenta. Agreement with experimental data is found to be good. This first model is then embedded (providing energy dependence) in a two-component eikonal model used to study elastic diffraction and unifying parton model and impact parameter formulations. We discuss the inclusion of a real part for the elastic amplitude, the removal of multiple diffraction zeros and the behavior of this second model up to the multi-TeV energy range (the Froissart bound is not saturated). We find excellent agreement with a large body of experimental data.

The cross sections for muon pair production in antiproton-nucleus and pion-nucleus collisions have been measured using a 125 GeV/c beam incident on a tungsten target. Both cross sections agree well with data scaled from other beam energies. The measured cross section for antiproton produced pairs is a factor of K = 2.45 larger than the predictions of the Drell-Yan model using structure functions measured by deep inelastic lepton scattering experiments. / The Drell-Yan formula has been inverted and the antiproton and pion valence structure functions have been extracted from the data. The shape of the antiproton structure function agrees well with the shape of the proton structure function measured by deep inelastic scattering experiments. The shape and magnitude of both the antiproton and the pion structure functions agree well with measurements made by other muon pair experiments.

Thesis (Ph. D.)--Florida State University, 2006. / Advisor: Susan K. Blessing, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Sept. 22, 2006). Document formatted into pages; contains xiv, 138 pages. Non-Latin script record Includes bibliographical references.

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Copies of author's earlier publications inserted. / Bibliography: leaves 129-137. / 137 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The subject of this thesis is the application of the MIT bag model to nuclear and particle physics. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1997

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matermáticas. Programa de Pós-graduação em Física, Florianópolis, 2016. / Made available in DSpace on 2016-09-20T05:06:05Z (GMT). No. of bitstreams: 1 340358.pdf: 834249 bytes, checksum: f7763d5869e3f7424956104ed9ab2028 (MD5) Previous issue date: 2016 / O estudo da fenomenologia de colisões hadrônicas apresentou um crescimento espetacular em qualidadee quantidade nos últimos anos com o surgimento dos aceleradores de partículas modernos,notadamente com o LHC. Isso permitiu a observação de novos fenômenos físicos, entre os quais temosas interações multi-partônicas (MPI), onde destacamos o espalhamento duplo de pártons (DPS).Nesta dissertação, nós estudamos a contribuição do DPS com base no processo gg ! gg nos níveisde energia do LHC. O processo DPS, que pode ser descrito como sendo um processo perturbativopode ocorrer quando dois pares de pártons interagem entre si em uma mesma colisão próton - próton.Após fazermos uma breve introdução no Cap. 1, no Cap. 2 apresentamos os aspectos básicos da QCDperturbativa, das partículas fundamentais e das interações elementares da natureza. No Cap. 3, o espalhamentoprofundamente inelástico é revisto, bem como as interações de espalhamento simples depártons (SPS) e de DPS são abordadas. O Cap. 4 é dedicado à análise da seção de choque total, bemcomo de alguns modelos teóricos já existentes. No Cap. 5, os resultados reproduzidos e calculadossão apresentados e discutidos. Encontrou-se a razão entre as constantes dos termos dominantes dasseções de choque calculadas via SPS e DPS, diferindo por um fator bem definido. No Cap. 6 está aconclusão deste estudo e as perspectivas de trabalho são discutidas, incluindo a análise do significadodo fator encontrado e o desenvolvimento de resultados teóricos para a seção de choque total.<br> / Abstract: The study of the phenomenology of hadron collisions presented a spectacular growth in quality and quantity in the last years with the appearance of modern particle accelerators, specially, the LargeHadron Collider. This allowed the observation of new physical phenomena, among which we have the multi-parton interactions (MPI), where we highlight the double parton interactions (DPS). In this dissertation, we study the contribution of the DPS from the process gg-gg at the energy levels of LHC. The DPS process, that can be described as a perturbative process, can occur when two pairs of partons interact themselves in a same proton-proton collision. After we make a brief introduction in Ch. 1, in Ch. 2, we show the basics aspects of the perturbative Quantum Chromo Dynamics (QCD),the fundamental particles and the elementary interactions of the Nature. In the Ch. 3, the deeply inelastic scattering is revisited, as well single parton scattering (SPS) and DPS interactions. Ch. 4 is devoted to the total cross section analysis, as well some existing theoretical models. In the Ch. 5, there produced and calculated results are shown and discussed. The ratio between the constants of the dominant terms in SPS and DPS cross sections was found, it is a well defined factor. In Ch. 6 theconclusion of this work is presented and future work is discussed, including analysing the meaning of the factor found and developing theoretical results for the total cross section.

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Orientador: Adriano Antonio Natale / Banca: Juan Carlos Montero Garcia / Banca: Márcio José Menon / Resumo: Discutiremos alguns modelos fenomenológicos baseados na QCD perturbativa que tentam descreve a seção de choque total hadrônica. Falaremos sobre as principais características dos espalhamentos hadrônicos, como o crescimento da seção de choque total com a energia devido ao aumento no número de jatos, e o decrescimento da seção de choque total a baixas energias. Mostraremos a inviabilidade do tratamento perturbativo de QCD para o cálculo da seção de choque total hadrônica. Estudaremos alguns espalhamentos hadrônicos no limite de baixas energias utilizando informações não-perturbativas das propriedades do sistema, tal como o fato do gluon adquirir massa dinâmica nesta região. Averiguando propriedades e modelos que procuram descrever a seção de choque total hadrônica, obteremos idéias suficientes para propor um modelo que descreva a seção de choque total hadrônica real / Abstract: We discuss some phenomenological models based on perturbative QCD, that try to describe the total hadronic cross section. We comment on peculiarities of hadronic scattering, as the increase of cross section at high energies, as well as its decrease in low energies. Some of the problems of perturbative QCD to deal with the total cross section calculation are discussed. We discuss how non-perturbative QCD properties, as the generation of a dynamical gluon mass, can be introduced in the low energy limit of the total cross section calculation. Finally we propose a phenomenological way to modify the total hadronic cross section calculation with these non-perturbative information / Mestre

A computer program that symbolically generates and evaluates all Feynman diagrams required for scattering amplitude for exclusive processes is tested, corrected, extended, and brought to operational status. The sensitivity of perturbative QCD predictions for the nucleon form factors, ψ → pp̅, and 𝛾𝛾 → pp̅, to the theoretical uncertainties of the nucleon wave function and the form of the running coupling constant is investigated. A new prediction for the cross-section for 𝛾𝛾 → Δ++ Δ̅++ with sum-rule wave functions is presented. As a product of the development of the computer program, the quark amplitudes for meson-baryon scattering are obtained. Integrations of the quark amplitudes over wave functions are carried out by cutting off singularities. The numerical reliability of the integration and its sensitivity to the cut-off’s and the choice of wave function are investigated. / Ph. D. / incomplete_metadata