O objetivo deste artigoé introduzir alguns conceitos físicos utilizados no maior colisor de partículas do mundo (LHC) e demonstrar que esse equipamento não oferece risco algumà Terra. Esses conceitos serão tratados a partir de conteúdos abordados no Ensino Médio, servindo, desse modo, como incentivo as práticas docentes no ensino de física básica. Os tópicos abordados serão: raios cósmicos, mini-buracos negros, campos magnéticos, detectores de partículas, luminosidade, partícula de Higgs, cavidades de RF (rádio frequência), energia armazenada em diferentes formas e o modelo padrão das partículas elementares. Os cálculos apresentados aqui são apenas aproximações pois, na maioria destes, foram desconsiderados os efeitos relativísticos. Palavras-chave: física de partículas, aceleradores de partículas, ensino de física.The goal of this article is to introduce some physical concepts used in the largest particle collider in the world (LHC) and demonstrate that this equipment does not offer any risk to Earth. These concepts will be treated from content covered in high school, thus serving as an incentive to teaching practices in the basic Physics teaching. Topics covered will be: cosmic rays, mini-black holes, magnetic fields, particle detectors, luminosity, Higgs particle, RF (radio frequency) cavities, energy stored in different ways and the Standard Model of elementary particles. The calculations presented here are only approximations because, in most of these, were disregarded relativistic effects.

Neste artigo, vamos estudar alguns conceitos fundamentais em física de partículas através do estudo detalhado de um processo específico da Eletrodinâmica Quântica (QED): o espalhamento Bhabha em ordem dominante (Leading Order -LO). Este ocorre na interação entre um elétron e sua antipartícula, o pósitron, sendo um dos processos básicos da QED. Nossa escolha em trabalhar este processo deve-se a riqueza de detalhes proporcionada pelas duas possibilidades (canais) de interação, que servem para ilustrar o cálculo da interferência entre as possibilidades. Além disso, esse processo é utilizado para determinar a luminosidade de um determinado colisor, o que garante maior precisão nas medidas de outras grandezas relevantes para a análise das interações entre partículas. Finalmente, comparamos a predição da QED com os resultados do experimento DESY-PETRA-TASSO. Palavras-chave: física de partículas, processos elementares, eletrodinâmica quântica.In this article, we will look at some fundamental concepts in Particle Physics through the detailed study of a specific process of Quantum Electrodynamics (QED): the Bhabha scattering. It occurs in the interaction between an electron and its antiparticle, the positron, one of the basic QED processes. Our choice for work this process is due to the wealth of details provided by the two possibilities (channels) of interaction which serve to illustrate the calculation of interference between possibilities. Furthermore, this process is used to determine the luminosity of a particular collider, which ensures greater accuracy in measurements of other relevant quantities for the analysis of interactions between particles. Finally, comparing the QED prediction with the experimental results of the DESY-PETRA-TASSO experiment. Keywords: particle physics, elementary processes, quantum electrodynamics. IntroduçãoA divulgação científica de física de partículas, apesar das notícias apresentadas pela mídia nacional e internacional da descoberta do Bóson de Higgs pelo CERN, ainda não possui muitos livros em português. O que dificulta um pouco o interesse de alunos de graduação por tal tema. No entanto, há dois livros de divulgação científica, em português, de pesquisadores nesta área: "O Discreto Charme das Partículas Elementares"da Professora Maria Cristina Batoni Abdalla, destinado a pessoas leigas em física. E "O Cerne da Matéria"do Professor Rogério Rosenfeld, o qual relata toda a trajetória dos físicos e experimentos que culminaram na descoberta do Bóson de Higgs noticiada no dia 4 de Julho de 2012 pelo CERN. O livro deste professor é recomendado tanto para físicos de outras áreas quanto propriamente para pesquisadores desta área. Assim, a principal motivação deste artigo é fornecer um material em português bem como os có-digos e scripts necessários para reproduzir os valores e gráficos aqui apresentados. Por isso, direcionamos este texto para estudantes de graduação, nos primeiros anos, * Endereço de correspondência: fabio.kopp@ufrgs.br. que tenham interesse em aprofundar conhecimentos na fí...

The cooling mechanisms of a neutron star (hereafter referred to as NS) have the potential to reveal important features of superdense matter. The values of the surface temperatures are known for a good sample of NSs aged [Formula: see text] years and, with some exceptions, can be explained through standard cooling mechanisms (neutrinos and photons emissions without internal heating), as confirmed in our study. However, for older objects the surface temperatures are in some cases higher than expected, and it is necessary to consider some kind of internal heating to explain these results. With this objective, we revisit in this paper the kinetic mechanisms of heating in NSs considering fermionic dark matter (DM) heating, rotochemical heating and magnetic field decay. Our results indicate that NSs older than [Formula: see text] years, such as some “Black Widows” (BW — a subset of binary systems in which only the upper bounds of surface temperatures are known) and old pulsars, in contrast to younger NSs, exhibit much higher surface temperatures than the values predicted by these three heating mechanisms. Furthermore, by restricting the DM heating parameters to the current values that were fitted and/or measured for the local DM density, masses and NS radii, the models studied here also do not reproduce the upper limits of the temperatures from the surface of BWs or the actual temperatures of other ancient pulsars. We conclude that if the upper limits for BWs are close to real temperatures, dark heating will not represent a convincing explanation of these results, indicating that rotochemical mechanisms may be favored.

In this contribution, we study the nature of the quantum chromodynamics (QCD) phase transition in hybrid compact stars. In our approach, we consider a microscopic hadron-quark hybrid equation of state (EoS) to describe the structure of compact stars composed of a quark core and a hadronic shell assuming a structural first-order phase transition at their interface. Our primary purpose in this contribution is to delineate, for a hybrid compact star, the relevant ingredients of their EoSs that simultaneously have the required stiffness and satisfy the constraints of thermodynamics (stability conditions on the free energy, accordance with the laws of thermodynamics and Gibbs' criteria for phase equilibrium). The quark matter structural description is based on the standard MIT bag model, and for the hadron phase modeling, we consider a statistical model for the EoS, which consists of an ensemble of interacting nucleons in statistical equilibrium. In the calculations, the relativistic mean field approximation is used, and the parameters of the approach are taken from experimental data and from nuclear structure calculations. Moreover, exclusion volume effects are implemented in a thermodynamically consistent way so that the transition to uniform nuclear matter can be described in a physically coherent way. We investigate the implications on the structure of a compact hybrid star of considering a Bag constant dependence on the nuclear density, as well as subsidiary aspects of the nature of QCD phase transition as the Gibbs and Maxwell construction realizations of the first-order deconfinement phase transition inside a compact star and observational signals. K E Y W O R D Shybrid star, mean field theory, neutron star, nuclear force