Bibliography: p. 159-166. / There is a short introduction to the ideas of lattice theory, followed by an equally brief look at pure gauge QCD on the lattice. More details for either of these may be found in the references cited in each section, as well as in [143]. The bulk of this work deals with the problems encountered in placing fermions on to the lattice, and the techniques used for this purpose. The Nielsen-Ninomiya theorem is introduced, with a detailed treatment thereof relegated to an appendix. The two main fermion techniques, due to Wilson (1974); and Kogut and Susskind (1975) are dealt with in some detail. This is followed by a discussion of the construction of hadrons on the lattice, using either Wilson or Kogut-Susskind fermions. There is a chapter covering the algorithms used in numerical simulations of lattice QCD, with some examples illustrating them. The thesis concludes with a discussion of the results obtained thus far on the hadron spectrum, in both the quenched approximation as well as those obtained using dynamical quarks.

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The retention of quantum numbers in hadron jets was studied, and a model was constructed to infer the quantum numbers of the leading quark and antiquark in the the reaction e⁺e⁻ → qoqo → hadrons, from the quantum numbers of the final state particles. The method used involved taking a weighted average of the quantum numbers of the hadrons in the jet, with the weight assigned to each particle dependent on its kinemat-ical variables. The model was tested using the Lund Monte Carlo JETSET 7.1 at 80 GeV. It was found that in two jet events, it was possible to determine the sign of the charge of the leading partons with SO percent accuracy overall, and with greater than 94 percent accuracy in 41 percent of the events (using cuts on the weighted average to select the events). In light quark events (dd, uu, and ss), it was found that the quark jet and its flavour could be determined with about 48 percent precision and heavy quark tagging of cc and bb could be achieved in 38 and 63 percent of events respectively. In 15 percent of the light quark events, selected by consistency between the two back to back jets, successful determination of the quark jet and its flavour were obtained in 85 percent of events, with heavy quark contamination reduced to 12 and 6 percent of cc and bb events respectively. The model was also run on three jet events at 80 GeV. Although it was possible to identify one jet as a non-gluon jet (in particular the jet which subtends the largest angle with the other two jets) in 90 percent of events, it was not possible to determine which of the two remaining jets was the gluon jet. The sign of the electric charge of the non-gluon jet could be determined in 70 percent of events overall, and in 90 percent of a smaller group of 20 percent of events again using cuts on the weighted charge for the jets. The flavour of the non-gluon jet could be determined in 42 percent of events overall, and in 65 percent of a smaller group of 18 percent of events using consistency between the non-gluon jet and the other two jets, although heavy quark contamination was more significant. Finally, the accuracy with which the sign of the electric charge and flavour could be determined in two jet events at energies in the range 20 to 100 GeV was studied. It was found that as the centre of mass energy increased, the precision with which these properties could be inferred showed a marked increase. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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Reproduction de : Thèse de doctorat : Physique des particules : Lyon 1 : 2008. / Titre provenant de l'écran titre. Bibliogr. p. 229-233.

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

During the summer 2014, the HADES collaboration had the opportunity to measure pion collisions with different nuclei. These measurements were done with two objectives. The first being the investigations of hadrons with strange quarks and their behaviour at normal nuclear density. The analysis of this will concentrate specifically on φ meson and Λ baryon production. The focus on properties of baryonic resonances in the region of N(1520) and N(1535) formed the second objective. Special emphasis is put on beam line detectors which use different particle detection techniques. In particular, the scintillator based Hodoscope and diamond based Start detector will be discussed. There is also presented the analysis of π + p elastic scattering which is important for normalisation of the cross section of the reactions of interest. The measured elastic scattering yields are compared with dedicated simulations and previously published data. 1