O principal objetivo deste trabalho foi obter a produção das partículas estranhas K0, e em colisões entre íons pesados relativísticos para ÖsNN = 62.4 GeV, bem como estudar o comportamento sistemático dessa produção em função da energia. Para isso, utilizamos os dados provenientes da colisão de íons pesados relativísticos obtidos pelo experimento STAR do RHIC. O objetivo deste trabalho também foi o de estudar dois estágios específicos da evolução do fireball formado nessas colisões: os chamados freeze-out químico e térmico. Estes estágios (ou fases) foram estudadas a partir das razões entre diversas partículas e da distribuição de momento transversal das mesmas, comparando os resultados com previsões e ajustes de modelos térmicos, a fim de avaliar possíveis efeitos da formação de um Plasma de Quarks e Gluons (QGP) em equilíbrio térmico sobre os hádrons medidos pelo experimento. O freeze-out químico foi estudado a partir das razões entre abundâncias de partículas produzidas na colisão, que foram comparadas a ajustes de um modelo térmico que trata o fireball como um gás de hádrons em equilíbrio (THERMUS) e aos resultados de um modelo que não assume esse equilíbrio (SHM). Com essa abordagem, verificamos que o modelo THERMUS ajusta bem os dados experimentais para uma ampla faixa de energias de colisão, principalmente para 62.4 GeV. Os parâmetros termodinâmicos obtidos foram estudados em função da energia para verificarmos se há um comportamento suave do sistema ou mudanças abruptas. O estudo indicou que esse comportamento é suave com a energia. Ainda neste estudo do freeze-out químico, comparamos os resultados do modelo THERMUS com os resultados do modelo que considera o não ? equilíbrio químico, o SHM. Nesta comparação, a razão apresentou um comportamento interessante, sugerindo que a energias mais baixas o sistema se comporta conforme a prescrição do modelo SHM, enquanto que o modelo que considera o fireball como um gás de hádrons em equilíbrio, novamente, demonstrou melhor compatibilidade a energias mais altas, reafirmando aqui a indicação de uma possível formação de um sistema termalizado. O freeze-out cinético/térmico foi estudado com os espectros de momento transversal, considerando um modelo fenomenológico inspirado na hidrodinâmica. Os resultados mostram que eventos mais centrais apresentam uma velocidade de expansão maior e uma temperatura menor, condizente com uma fonte que tem um gradiente de pressão maior. Também foi observado que a partícula ? apresenta sempre uma temperatura maior que as outras partículas (p, ?, ?) indicando um desacoplamento anterior dessas partículas em relação às outras. Finalmente, estudamos a utilização do SVT para a reconstrução de V0s, procurando compreender a maneira correta de se utilizar este detector na análise. Os resultados mostram que a utilização desse detector pode levar a uma melhora na eficiência e na pureza durante a reconstrução dessas partículas. / The main goal of this work was to measure the production of the singly strange particles, such as K0, and in Au+Au collisions at ?sNN = 62.4 GeV, inserting these results in a systematic energy scan study. The data were obtained from the STAR detector, one of the RHIC experiments. In addition, we have used the particle production in these collision to study two specific stages of the fireball evolution: the chemical and kinetic freeze-outs. These two stages were studied comparing the ratio between different particles (strange or not) and also the transverse momentum distribution with thermal models fits in order to check possible effects of equilibrated Quark Gluon Plasma (QGP) in the hadron production. The chemical freeze-out was studied comparing the ratios between particles produced in the collision with two different thermal models: one which assumes a equilibrated hadron gas (THERMUS) and another one which assumes a possible non-equilibrated system (SHM). The experimental data were well described by the THERMUS model fit in a great range of energy collisions, mainly at 62.4 GeV. The thermodynamic parameters had been studied as function of the energy in order to verify if it has a smooth or abrupt behavior. The result indicated that this behavior is very smooth with energy. We also compared these results with SHM\'s predictions and, in this comparison, the ratio presented an interesting behavior, suggesting that at low energies the fireball consists of a non-equilibrated system, such as described by SHM model, whereas the model that considers the fireball as a equilibrated hadron gas. The kinetic freeze-out was studied with the transverse momentum spectra using a hydrodynamics inspired model. The results indicate that for the most central events there is a higher expanding velocity and a lower freeze-out temperature. It was also observed that for the particle, the freeze-out temperature is higher than the one for other particles (?, K, p) indicating an earlier decoupling of these particles from the fireball. Finally, we have studied the inclusion for the SVT in the V0 reconstruction analysis, trying to optimize this detector usage in the analysis. The results show that the inclusion of this detector in the analysis can improve the efficiency and purity of the V0 reconstruction in the STAR experiment.

The aim of relativistic heavy-ion collisions is to investigate the properties of the Quark-Gluon Plasma (QGP) phase, that is achieved at high-enough temperatures and/or densities. In this context, light on heavy-ion collisions (e. g. p-Pb) are used to assess Cold Nuclear Matter effects (CNM), while elementary hadronic collisions (e. g. proton-proton) provide tests for QCD (Quantum Chromodynamics) based calculations and baseline for studies with heavy- ions. Heavy quarks, i. e. charm and beauty, are very convenient in the characterization of the QGP. They are produced via initial hard parton-parton scatterings at the early stages of the collision and, therefore, they are a self-generated probe for the system created in the reaction. In this work the angular correlation between electrons from heavy-flavour hadron decays and charged particles was studied in pp (2.76 and 7 TeV) and p-Pb (5.02 TeV) collisions at the CERN Large Hadron Collider, using the ALICE detector. The correlation strengths were evaluated as a function of multiplicity in p-Pb collisions. In pp collisions the relative beauty (and charm) contribution to the total heavy-flavour decay electron yield was estimated using the measured correlation distribution and Monte Carlo templates. / O próposito de colisões entre íons pesados relativísticos é investigar as propriedades do plasma de quarks e gluons (QGP, do inglês Quark-Gluon Plasma). A transição de fase, de um estado hadrônico para o QGP, ocorre em regimes onde a temperatura e/ou densidade atingem um valor suficientemente alto. Neste contexto, colisões entre íons pesados e leves (por exemplo, p-Pb) permitem acessar efeitos devido à matéria nuclear fria (CNM, do inglês Cold Nuclear Matter) e colisões elementares (por exemplo, próton-próton) são usadas como referência para estudos com íons pesados, além de proporcionarem testes para cálculos de QCD perturbativa. Quarks pesados, isto é charm e bottom, são ferramentes muito convenientes no estudo e caracterização do QGP. Essas partículas são produzidas através de espalhamento duro nos instantes iniciais da colisão e, portanto, elas atuam como uma sonda externa para o sistema criado na reação. Esse trabalho consiste no estudo da correlação angular entre elétrons oriundos de quarks pesados e partículas carregadas, em colisões pp (2.76 e 7 TeV) e p-Pb (5.02 TeV), no acelerador LHC (do inglês Large Hadron Collider) do CERN, usando o detector ALICE (do inglês A Large Ion Collider Experiment). A distribuição angular mencionada foi medida em função da multiplicidade do evento, no caso de colisões p-Pb. Em colisões pp, a contribuição relativa de quarks charm e bottom para o total de elétrons provenientes de quarks pesados foi estimada usando a função de correlação obtida.

Neste trabalho são reportadas medidas realizadas no detector PHENIX do RHIC sobre J/Psi em colisões p+p e Au+Au a s^(1/2) = 200 GeV na região de rapidez central e Psi\' em colisões p+p nas mesmas condições. As medidas incluem a dependência com o momento transverso da produção de charmônio e o fator de modificação nuclear de J/Psis para vários regimes de centralidade de colisão. / This work reports measurements done by the PHENIX detector at RHIC about J/Psi in p+p and Au+Au collisions at s^(1/2) = 200 GeV in the mid-rapidity range and Psi\' in p+p collisions in the same conditions. The measurements include the transverse momentum dependence of charmonium production and J/Psi nuclear modification factor in different centrality regimes.

O plasma de quarks e glúons é um assunto que vem sendo muito estudado nos últimos anos, devido ao advento dos colisores de partículas modernos e os avanços nas pesquisas relacionadas a estrelas compactas. Assim, nesta tese tivemos como objetivo principal o estudo deste plasma. Para isto, aprimoramos uma equação de estado desenvolvida pelo nosso grupo, na qual foi adicionada a interação com um campo magnético constante. De posse desta nova equação de estado, que é formulada a partir da técnica de aproximação de campo médio, fizemos diversas aplicações. Em particular, no estudo de propagação de ondas lineares e não lineares, com o objetivo de verificar se a causalidade e estabilidade são respeitadas. Resolvemos a equação de Tolman-Oppenheimer-Volkoff para obter o diagrama massa-raio para uma estrela de quarks compacta. Estudamos como é a evolução temporal do Universo primordial resolvendo as equações de Friedmann e a evolução temporal de bolhas do plasma de quarks e glúons no gãs de hádrons (e também de bolhas de gás de hádrons no plasma de quarks e glúons) utilizando a equação de Rayleigh-Plesset relativística. / The quark gluon plama is a subject that has been actively studied in recent years, due to the advent of modern particle colliders and advances in research related to compact stars. Thus, in this thesis we had as main goal the study of this plasma. For this, we improved an equation of state developed by our group, where an interaction with a constant magnetic field was added. With this new equation of state, which is formulated from the mean field approximation technique, we made several applications. As in the study of propagation of linear and non-linear waves, with the goal of verifying whether the causality and stability are respected. We solved the Tolman-Oppenheimer-Volkoff equation to obtain the mass-radius diagram for a compact quark star. We study how the temporal evolution of the primordial Universe by solving Friedmanns equations and the temporal evolution of bubbles of quark gluon plasma in a hadrons gas (and also of bubbles of hadrons gas in a quark gluon plasma) using the relativistic Rayleigh-Plesset equation.

L'expérience ALICE, qui utilise les collisions d'ions lourds ultra-relativistes produites par le LHC au CERN, est dédiée à l'étude d'un nouvel état de la matière nucléaire, qui pourrait se présenter sous la forme d'un plasma de quarks et de gluons (QGP). Parmi les sondes portant des informations sur les propriétés de ce milieu, celles relatives à la production des jets de grande impulsion transverse sont particulièrement intéressantes. L'analyse présentée dans cette thèse s'intéresse aux évènements photon-jet, qui comportent un photon de grande impulsion transverse avec un jet émis dans la direction opposée. Ce dernier est issu de la fragmentation d'un parton, une fois qu'il a traversé le QGP. La thèse comprend une étude des observables pertinentes pour la mesure des corrélations photon-hadron ainsi qu'une analyse des premières données du LHC en collisions proton-proton. Des résultats préliminaires sur l'impulsion transverse des partons incidents et la fonction de corrélation ont ainsi été obtenus.

<p>Ultrarelativistic heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) are thought to have produced a state of matter called the Quark-Gluon-Plasma (QGP). The QGP forms when nuclear matter governed by Quantum Chromodynamics (QCD) reaches a temperature and baryochemical potential necessary to achieve the transition of hadrons (bound states of quarks and gluons) to {it deconfined} quarks and gluons. Such conditions have been achieved at RHIC, and the resulting QGP created exhibits properties of a near perfect fluid. In particular, strong evidence shows that the QGP exhibits a very small shear viscosity to entropy density ratio &eta/s, near the lower bound predicted for that quantity by Anti-deSitter space/Conformal Field Theory (AdS/CFT) methods of &eta/s = $hbar$/ 4 &pi $k_B$ where $hbar$ is Planck's constant and $k_B$ is Boltzmann's constant. As the produced matter expands and cools, it evolves through a phase described by a hadron gas with rapidly increasing $eta/s$.</p><p>This thesis presents robust calculations of $eta/s$ for hadronic and partonic media as a function of temperature using the Green-Kubo formalism. An analysis is performed for the behavior of $eta/s$ to mimic situations of the hadronic media at RHIC evolving out of chemical equilibrium, and systematic uncertainties are assessed for our method. In addition, preliminary results are presented for the bulk viscosity to entropy density ratio $zeta/s$, whose behavior is not well-known in a relativistic heavy ion collisions. The diffusion coefficient for baryon number is investigated, and an algorithm is presented to improve upon the previous work of investigation of heavy quark diffusion in a thermal QGP. </p><p>By combining the results of my investigations for $eta/s$ from our microscopic transport models with what is currently known from the experimental results on elliptic flow from RHIC, I find that the trajectory of $eta/s$ in a heavy ion collision has a rich structure, especially near the deconfinement transition temperature $T_c$. I have helped quantify the viscous hadronic effects to enable investigators to constrain the value of $eta/s$ for the QGP created at RHIC.</p> / Dissertation

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 115-121).

We study particle production and its density evolution and equilibration in hot dense medium, such as hadronic gas after quark gluon plasma hadronization and relativistic electron positron photon plasma. For this study we use kinetic momentum integrated equations for particles density evolution with Lorentz invariant reaction rates. We extend these equations, used before for two-to-two particles reactions (1 + 2 ↔ 3 + 4), to the case of two-to-one and backward reactions (1 + 2 ↔ 3). One type of hot dense medium, which we study, is hadronic gas produced at quark gluon plasma hadronization in heavy ions collisions in SPS, RHIC and LHC experiments. We study hadron production at quark gluon plasma hadronization and their evolution in thermal hadronic gas phase. We consider non-equilibrium hadronization model, for which the yields of the light quark hadrons are defined by entropy conservation. Yields of hadrons containing heavier (strange, charm, bottom) quarks are mainly controlled by flavor conservation. We predict yields of charm and bottom hadrons within this non-equilibrium statistical hadronization model. Then we use this non-equilibrium hadronization as the initial condition in the study of hadronic kinetic phase. During this time period some hadronic resonances can be produced in lighter hadrons fusion. This reaction is opposite to resonance decay. Production of resonances is dominant over decay if there is non-equilibrium excess of decay products. Within this model we explain apparently contradictory experimental results reported in RHIC experiments: ∑(1385) yield is enhanced while ∧(1520) yield is suppressed compared to the statistical hadronization model expectation obtained without kinetic phase. We also predict Δ(1232) enhancement. The second type of plasma medium we consider is the relativistic electron position photon plasma (EP³) drop. This plasma is expected to be produced in decay of supercritical field created in ultrashort laser pulse. We study at what conditions this plasma drop is opaque for photons and therefore may reach thermal and chemical equilibrium. Further we consider muon and pion production in this plasma also as a diagnostic tool. Such heavy particles can be diagnostic tool to study the properties of EP³ plasma, similar to the role taken by heavy hadrons production in heavy ions collisions. Finally all these theoretical developments can be applied to begin a study of particles evolution in early universe in temperatures domain from QGP hadronization (160 MeV) to nucleosynthesis (0.1 MeV). The first results on pion equilibration are presented here.

<p>Cutting edge research problems require the use of complicated and computationally expensive computer models. I will present a practical overview of the design and analysis of computer experiments in high energy nuclear and astro phsyics. The aim of these experiments is to infer credible ranges for certain fundamental parameters of the underlying physical processes through the analysis of model output and experimental data.</p><p>To be truly useful computer models must be calibrated against experimental data. Gaining an understanding of the response of expensive models across the full range of inputs can be a slow and painful process. Gaussian Process emulators can be an efficient and informative surrogate for expensive computer models and prove to be an ideal mechanism for exploring the response of these models to variations in their inputs.</p><p>A sensitivity analysis can be performed on these model emulators to characterize and quantify the relationship between model input parameters and predicted observable properties. The result of this analysis provides the user with information about which parameters are most important and most likely to affect the prediction of a given observable. Sensitivity analysis allow us to identify what model parameters can be most efficiently constrained by the given observational data set.</p><p>In this thesis I describe a range of techniques for the calibration and exploration of the complex and expensive computer models so common in modern physics research. These statistical methods are illustrated with examples drawn from the fields of high energy nuclear physics and galaxy formation.</p> / Dissertation

Techn. Univ., Diss., 2002--Darmstadt