Azimuthal jet flavor tomography with CUJET2.0 of nuclear collisions at RHIC and LHC

A perturbative QCD based jet tomographic Monte Carlo model, CUJET2.0, is presented to predict jet quenching observables in relativistic heavy ion collisions at RHIC/BNL and LHC/CERN energies. This model generalizes the DGLV theory of flavor dependent radiative energy loss by including multi-scale running strong coupling effects. It generalizes CUJET1.0 by computing jet path integrations though more realistic 2+1D transverse and longitudinally expanding viscous hydrodynamical fields contrained by fits to low $p_T$ flow data. The CUJET2.0 output depends on three control parameters, $(\alpha_{max},f_E,f_M)$, corresponding to an assumed upper bound on the vacuum running coupling in the infrared and two chromo-electric and magnetic QGP screening mass scales $(f_E \mu(T), f_M \mu(T))$ where $\mu(T)$ is the 1-loop Debye mass. We compare numerical results as a function of $\alpha_{max}$ for pure and deformed HTL dynamically enhanced scattering cases corresponding to $(f_E=1,2, f_M=0)$ to data of the nuclear modification factor, $R^f_{AA}(p_T,\phi; \sqrt{s}, b)$ for jet fragment flavors $f=\pi,D, B, e$ at $\sqrt{s}=0.2-2.76$ ATeV c.m. energies per nucleon pair and with impact parameter $b=2.4, 7.5$ fm. A $\chi^2$ analysis is presented and shows that $R^\pi_{AA}$ data from RHIC and LHC are consistent with CUJET2.0 at the $\chi^2/d.o.f< 2$ level for $\alpha_{max}=0.23-0.30$. The corresponding $\hat{q}(E_{jet}, T)/T^3$ effective jet transport coefficient field of this model is computed to facilitate comparison to other jet tomographic models in the literature. The predicted elliptic asymmetry, $v_2(p_T;\sqrt{s},b)$ is, however, found to significantly underestimated relative to RHIC and LHC data. We find the $\chi^2_{v_2}$ analysis shows that $v_2$ is very sensitive to allowing even as little as 10\% variations of the path averaged $\alpha_{max}$ along in and out of reaction plane paths.Comment: 87 pages, 32 figures; v3: typos corrected, new references and discussions included; accepted by JHE

Jet quenching in Quark Gluon Plasma: flavor tomography at RHIC and LHC by the CUJET model

A new jet tomographic model and numerical code, CUJET, is developed in this thesis and applied to the phenomenological study of the Quark Gluon Plasma produced in Heavy Ion Collisions

Jet Flavor Tomography of Quark Gluon Plasmas at RHIC and LHC

A new Monte Carlo model of jet quenching in nuclear collisions, CUJET1.0, is applied to predict the jet flavor dependence of the nuclear modification factor for fragments {\it $f=\pi,D,B,e^-$} from quenched jet flavors {\it $g,u,c,b$} in central collisions at RHIC and LHC. The nuclear modification factors for different flavors are predicted to exhibit a novel level crossing pattern over a transverse momentum range $5< p_T< 100$ GeV which can test jet-medium dynamics in quark gluon plasmas.Comment: 4 pages, 3 figure

Estudo da influência dos ciclos térmicos na microestrutura e propriedades mecânicas de juntas soldadas por fricção axial com anel rotativo utilizando tubos API 5L X65

Os dutos rígidos usados na indústria do petróleo são geralmente unidos por processos de soldagem a arco elétrico de forma automática, semiautomática ou manual. Porém, a soldagem por fricção pode ser uma alternativa potencial aos processos baseados na fusão dos materiais, por se tratar de um processo de soldagem no estado sólido e apresentar diversas vantagens no que diz respeito às propriedades metalúrgicas. Sendo assim, o foco principal deste trabalho é a aplicação do processo de soldagem por fricção axial com anel rotativo para união de tubos API 5L X65. A utilização desta técnica de união atendeu boa parte dos requisitos normativos, porém, foi observado o crescimento de grão austenítico e formação de microconstituintes que favoreceram a fratura por clivagem, associada a baixa energia absorvida em ensaios de tenacidade ao impacto. As regiões próximas à interface de soldagem foram expostas às temperaturas mais elevadas durante o ciclo termomecânico da soldagem, sendo mais criticamente afetadas. Como consequência, visando o completo entendimento dos mecanismos que levaram à redução da tenacidade, foi realizada uma avaliação criteriosa dos aspectos microestruturais que compõem as diferentes regiões da solda. Em um primeiro momento foi avaliada a influência do ciclo térmico da soldagem por fricção com diferentes condições de aportes térmicos, resultantes de combinações de parâmetros de soldagem definidas com o suporte da simulação numérica por elementos finitos. Posteriormente, foi testada a adoção de um tratamento térmico pós-soldagem visando elevar a tenacidade e qualificar a união soldada. A caracterização do material dos tubos e das juntas soldadas foi realizada por meio de ensaios de tração, tração a quente em Gleeble e de tenacidade ao impacto Charpy. Além de análises microestruturais em microscópio ótico, microscópio eletrônico de varredura (MEV), pela técnica de electron backscatter diffraction (EBSD) e fractografias. Observou-se que a redução no aporte térmico da soldagem contribui para mitigar o crescimento de grão e ocorrência de textura cristalográfica em regiões que apresentaram baixa tenacidade. Porém, apenas a partir do tratamento térmico de normalização realizado após a soldagem foi possível alcançar os requisitos mínimos para a qualificação técnica da união soldada.Pipelines currently used in the oil and gas industry are joined by automatic, semi-automatic, or manual arc welding processes. However, it is known that friction welding can be a potential alternative to these processes because it is a solid-state welding process and shows several advantages for the metallurgical properties. Therefore, this work aims to employ pipeline girth friction welding for joining a couple of API 5L X65 pipes and evaluate the thermo-mechanical influence of the process on the welded joint’s properties. Previous results revealed that the use of the abovementioned joining technique in high-strength and low-alloy steels is viable and partially complies with the standard requirements for welded joint properties, such as minimum tensile strength, upper and lower hardness limits, and defect-free joints. However, the performance of some specimens in impact toughness tests showed a tendency to form fragile and susceptible microstructures, lowering the fracture energy in regions close to the weld interface. Consequently, these results made necessary a more careful analysis of the microstructural characteristics that make up the welded region, for a full understanding of the issues that cause the impact toughness decrease in some critical regions a careful analysis of the microstructural characteristics. First, aimed to evaluate the influence of different heat input conditions of friction welding process, employing welding parameters established with the support of numerical simulation by finite elements. In addition, the influence of a post-welding heat treatment was evaluated. The analyses was carried out through mechanical tests used in the technical qualification of welded joints employing API 5L X65 pipes, and microstructural analyzed by optical microscope, Scanning Electronic Microscope (SEM), Electron Backscatter Diffraction (EBSD) and fractographies, in welds and pipe material. Through these analyses, it was observed that a reduced heat input condition mitigated the excessive grain growth, and occurrence of crystallographic texture in regions that showed a reduced toughness. However, the technical qualification according to normative recommendations was reached by application of a post-weld heat treatment

Quarkonium Results in PbPb Collisions at CMS

We summarize the results from the study of charmonium and bottomonium via the dimuon decay channel in PbPb collisions with the CMS experiment. We discuss the observation of sequential suppression of the Upsilon states. We present preliminary results of prompt J/psi and psi' production, as well as of non-prompt J/psis coming from the weak decay of b-quarks. This latter measurement is sensitive to b-quark energy loss. We discuss the results and compare to model predictions.Comment: 8 pages, 4 figures. Proceedings of 29th Winter Workshop on Nuclear Dynamic