Mecanismos de reaquecimento interno em estrelas de nêutrons

Neste trabalho revisitamos inicialmente, de maneira crítica, quatro modelos da literatura que descrevem estrelas compactas contendo quarks como sua composição primordial. Mais precisamente, consideramos neste estudo os modelos MIT, vMIT, CFL, CSS (que corresponde a uma parametrização de matéria de quarks) e CDQP, com vistas a construirmos, de uma forma consistente, equações de estado que descrevem estrelas de quarks e estrelas híbridas, bem como transições de fase e que reproduzam os resultados mais recentes da relação massa-raio e da massa máxima estelar. Como resultado deste estudo identificamos, à luz dos resultados observacionais mais recentes, pontos de convergência e de divergência entre os modelos abordados, visando com isto, em estudos futuros, o aprimoramento dos tratamentos formais abordados. Posteriormente, estudamos estrelas compactas híbridas, e em particular as estrelas gêmeas (caracterizadas por massas idênticas e raios distintos), cuja composição contempla uma crosta nuclear composta por hádrons e um núcleo central composto por quarks. Na descrição da parte hadrônica usamos a parametrização NL3 do modelo HDQ-II, que é acrescida de termos não lineares envolvendo acoplamentos do méson isoescalar-escalar σ. Na parte interna central, para a matéria de quarks, consideramos uma descrição baseada nos modelo MIT, vMIT, CFL, CDQP e a parametrização CSS, no âmbito da construção de Maxwell e, como novidade, ajustes e parametrizações cuja consistência formal supera ou questiona algumas das limitações encontradas na literatura. Os resultados obtidos nesta tese para a massa máxima e para a relação massa-raio de estrelas híbridas e estrelas gêmeas estão em bom acordo com os dados obervacionais. Finalmente, com o intuito de obter previsões para as temperaturas limite de estrelas de nêutrons antigas, incluindo estrelas do tipo Viúva Negra, apresentamos um estudo original que compara três modelos de reaquecimento interno, envolvendo contribuições cinéticas e de aniquilação de matéria escura e decaimento do campo magnético. Para estrelas de nêutrons jovens, esses mecanismos mostram-se pouco relevantes para descrever suas temperaturas limites. No entanto, para estrelas mais antigas, descobrimos que o processo rotoquímico é o melhor candidato para explicar as temperaturas de superfície dessas estrelas maduras, uma vez que o decaimento do campo magnético implica em uma diminuição, de maneira constante, nos valores da temperatura na superfície estelar, Ts. De outra feita, os resultados de nosso trabalho para a luminosidade estelar são consistentes com uma temperatura de superfície aproximadamente constante. Demonstramos, por fim, que as previsões dos modelos para a temperatura estelar de superfície mostram-se expressivas, — de até três ordens de magnitude. As diferenças mais dramáticas são encontradas no caso das estrelas do tipo Viúva Negra: todos os mecanismos de aquecimento abordados nesta tese mostram-se limitados para descrever suas temperaturas de superfície, mesmo que estas temperaturas estivessem bem abaixo dos limites superiores atuais, e que as idades estelares excedessem poucos giga-anos.In this work, we initially revisit, in a critical way, four models from the literature that describe compact stars containing quarks as their primordial composition. More precisely, in this study we consider the MIT, vMIT, CFL, CSS (which corresponds to a parameterization of quark matter) and CDQP models in order to build, in a consistent way, equations of state that describe quark stars and hybrid stars , as well as phase transitions and that reproduce the most recent results of the mass-radius ratio and the maximum stellar mass. As a result of this study, we identified, in the light of the most recent observational results, points of convergence and divergence between the approached models, aiming with this, in future studies, the improvement of the formal treatments approached. Subsequently, we studied hybrid compact stars, and in particular twin stars (characterized by identical masses and different radii), whose composition includes a nuclear crust composed of hadrons and a central core composed of quarks. In the description of the hadronic part we use the NL3 parameterization of the HDQ-II model, which is added by non-linear terms involving couplings of the isoscalar-scalar meson σ. In the central internal part, for the matter of quarks, we consider a description based on the MIT model, vMIT, CFL, CDQP and the CSS parameterization, within the framework of Maxwell’s construction and, as a novelty, adjustments and parameterizations whose formal consistency overcomes or questions some limitations found in the literature. The results obtained in this thesis for the maximum mass and for the mass-radius ratio of hybrid stars and twin stars are in good agreement with the observational data. Finally, in order to obtain predictions for the surface temperatures of ancient neutron stars, including Black Widow stars, we present an original study that compares three models of internal reheating, involving kinetic and annihilation contributions from dark matter and field decay magnetic. For young neutron stars, these mechanisms are not very relevant to describe their temperature limits. However, for older stars, we found that the rotochemical process is the best candidate to explain the surface temperatures of these mature stars, since the decay of the magnetic field implies a constant decrease in the stellar surface temperature values, Ts. Otherwise, the results of our work for stellar luminosity are consistent with an approximately constant surface temperature. Finally, we demonstrate that the model predictions for the real stellar surface temperature are expressive, — of up to three orders of magnitude. The most dramatic differences are found in the case of Black Widow stars: all heating mechanisms addressed in this thesis are limited to describe their surface temperatures, even if these temperatures were well below the current upper limits, and that the ages stars exceeded a few giga-years

Central exclusive χc,bproduction at high energy colliders and gluon saturation approach

The central exclusive production of χcand χbat the LHC, RHIC and Tevatron energies is analyzed, using the recent unintegrated parton distribution (UGDs) functions available in the package TMDlib. Comparison with data is performed, which tests the underlying assumptions basing the theoretical approach and it can constrain the unintegrated gluon distribution function at the small-xregion. Predictions for LHC energies using recent UGDs based in CCFM formalism are provided. It is explored the underlying uncertainties on this production as the choice for the unintegrated gluon distribution and factorization scale is done. Moreover, based on the parton saturation model for the gluon distribution, analytical expressions for the rapidity distributions are proposed. The prompt production of J/ψ+γand Υ+γis computed for the first time for LHC energies within the very same formalism used for χproductio

Photoproduction of upsilon states in ultraperipheral collisions at the CERN Large Hadron Collider within the color dipole approach

The exclusive photoproduction of upsilon state ϒð1SÞ and its radially excited states ϒð2S; 3SÞ is investigated in the context of ultraperipheral collisions at the LHC energies. Predictions are presented for their production in proton-proton, proton-nucleus, and nucleus-nucleus collision at the energies available at the LHC Run 2. The rapidity and transverse-momentum distributions are shown, and the robustness of the model is tested against the experimental results considering ψð1S; 2SÞ and ϒð1SÞ states. The theoretical framework considered in the analysis is the light-cone color dipole formalism, which includes consistently parton saturation effects and nuclear shadowing corrections

Soft diffraction within the QCD color dipole picture

In this work we consider the QCD parton saturation models to describe soft interactions at the high energy limit. The total and elastic cross sections, as well as the elastic slope parameter, are obtained for proton-proton and pion-proton collisions and compared to recent experimental results. The analyses are done within the color dipole formalism, taking into account saturation models which have been tested against deep inelastic scattering data. The main point is that the matching between soft and hard interaction occurs in the saturation region which can be described by high density QCD approaches. Discussion is performed on the main theoretical uncertainties associated with calculations

Coherent and incoherent production of vector mesons in ultraperipheral collisions of xenon ions within the QCD parton saturation approach

In this paper, we analyze the exclusive vector meson photoproduction in the recent run using xenon ions at energy of 5.44 TeV performed by the Large Hadron Collider. We focus on the ultraperipheral collisions and provide theoretical predictions for coherent and incoherent cross sections within the color dipole approach and gluon saturation framework. The rapidity distribution is investigated in both cases and comparison to other approaches available in the literature is completed. We show that the expected yields are enough to perform reliable cross section measurements for light mesons as ρ0 and ϕ

Coherent and incoherent production of vector mesons in ultraperipheral collisions of xenon ions within the QCD parton saturation approach

In this paper, we analyze the exclusive vector meson photoproduction in the recent run using xenon ions at energy of 5.44 TeV performed by the Large Hadron Collider. We focus on the ultraperipheral collisions and provide theoretical predictions for coherent and incoherent cross sections within the color dipole approach and gluon saturation framework. The rapidity distribution is investigated in both cases and comparison to other approaches available in the literature is completed. We show that the expected yields are enough to perform reliable cross section measurements for light mesons as ρ0 and ϕ

Coherent and incoherent Upsilon production in ultraperipheral collisions at the Large Hadron Collider

The exclusive photoproduction of ϒðnSÞ states was calculated in ultraperipheral collisions for coherent and incoherent process in PbPb at sNN p ¼ 5.5 TeV. Different dipole models were compared in the theoretical framework of light-cone color dipole formalism. Moreover, we calculated the differential cross section for the Upsilon states and their total cross section for two intervals of rapidity: jyj ≤ 4 4 and 2 ≤ y ≤ 4.5. A systematic study is done on the theoretical uncertainties associated to the production, and predictions are presented for the first time for the incoherent cross section of the radially excited states

Coherent and incoherent Upsilon production in ultraperipheral collisions at the Large Hadron Collider

The exclusive photoproduction of ϒðnSÞ states was calculated in ultraperipheral collisions for coherent and incoherent process in PbPb at sNN p ¼ 5.5 TeV. Different dipole models were compared in the theoretical framework of light-cone color dipole formalism. Moreover, we calculated the differential cross section for the Upsilon states and their total cross section for two intervals of rapidity: jyj ≤ 4 4 and 2 ≤ y ≤ 4.5. A systematic study is done on the theoretical uncertainties associated to the production, and predictions are presented for the first time for the incoherent cross section of the radially excited states

Central exclusive χc,bproduction at high energy colliders and gluon saturation approach

The central exclusive production of χcand χbat the LHC, RHIC and Tevatron energies is analyzed, using the recent unintegrated parton distribution (UGDs) functions available in the package TMDlib. Comparison with data is performed, which tests the underlying assumptions basing the theoretical approach and it can constrain the unintegrated gluon distribution function at the small-xregion. Predictions for LHC energies using recent UGDs based in CCFM formalism are provided. It is explored the underlying uncertainties on this production as the choice for the unintegrated gluon distribution and factorization scale is done. Moreover, based on the parton saturation model for the gluon distribution, analytical expressions for the rapidity distributions are proposed. The prompt production of J/ψ+γand Υ+γis computed for the first time for LHC energies within the very same formalism used for χproductio

Photoproduction of upsilon states in ultraperipheral collisions at the CERN Large Hadron Collider within the color dipole approach

The exclusive photoproduction of upsilon state ϒð1SÞ and its radially excited states ϒð2S; 3SÞ is investigated in the context of ultraperipheral collisions at the LHC energies. Predictions are presented for their production in proton-proton, proton-nucleus, and nucleus-nucleus collision at the energies available at the LHC Run 2. The rapidity and transverse-momentum distributions are shown, and the robustness of the model is tested against the experimental results considering ψð1S; 2SÞ and ϒð1SÞ states. The theoretical framework considered in the analysis is the light-cone color dipole formalism, which includes consistently parton saturation effects and nuclear shadowing corrections