We analyze the hadronic phase of QCD using effective thermal field theory techniques. Our goal is to investigate the medium created in heavy ion collisions by calculating the electromagnetic emissivity of strongly interacting matter in the hadronic phase. We proceed through examining the vector meson properties in a thermal bath where the temperature reaches deconfinement and chiral symmetry is restored. In particular we observe the behavior of the rho spectral function in thermal medium and use it as a probe to examine the thermal environment generated in the collision.

No description available.

We study the hadronic phase of Quantum Chromodynamics within a formalism that uses strongly interacting resonances in the Regge theory approach. Our aim is to investigate the properties of the medium created in a relativistic nucleus-nucleus collision, using the electromagnetic decays of vector mesons as probe. To do so, we first layout the foundations of Regge theory, which is then used to calculate the in-medium properties of vector mesons. This methodology will be used to calculate for the first time the properties of the &phis; meson in a hadronic medium. The properties are contained within the imaginary part of the propagator (IMPP). Since it is related to electromagnetic decay via vector meson dominance, the IMPP is a probe of strongly interacting hadron gas created in the collision.

No description available.

Aiming at a systematic inclusion of pseudoscalar and vector mesons as active degrees of freedom in an effective Lagrangian, studies have been performed in this thesis concerning the foundations of such an effective Lagrangian as well as tree-level and beyond-tree-level calculations. Hereby, vector mesons are described by antisymmetric tensor fields. First, an existing power counting scheme for both pseudoscalar and vector mesons is extended to include the pseudoscalar-meson singlet in a systematic way. Based on this, tree-level calculations are carried out which are in good agreement with the available experimental data and several processes are predicted. In particular, the ω-π0 transition form factor is in better agreement with experimental data than the prediction done in the vector-meson-dominance model. Furthermore, a Lagrangian with vector mesons is used together with the leading contributions of chiral perturbation theory in order to calculate tree-level reactions in the sector of odd intrinsic parity. It turns out that both the Lagrangian with vector mesons and the Lagrangian of chiral perturbation theory are needed to describe experimental data. Additionally, a feasibility check for one-loop calculations with pseudoscalar and vector mesons in the loop is performed. Thereby, only a limited number of interaction terms in the Lagrangian with vector mesons is used. The results are used to both renormalise the low-energy constants of chiral perturbation theory up to chiral order Q4 and to determine the influence of loops with vector mesons on masses and decay constants of pseudoscalar mesons.

No description available.

No description available.

Este trabalho é dedicado ao estudo da fotoprodução de mésons vetoriais em colisões ultra-periféricas. Este estudo foi realizado por meio do código de Monte Carlo CRISP, o qual recebeu atualizações e implementações a fim de permitir o cálculo das colisões. Foi elaborado um modelo para a geração do espectro de energia dos fótons equivalentes que deve interagir com o alvo, bem como foram introduzidos novos canais de foto-absorção para a fotoprodução de múltiplos píons, os quais são essenciais à reprodução dos fenômenos nucleares em altas energias. Ao todo 84 canais foram introduzidos. Foi estudada, em particular, a produção do méson J/$\\psi$ em colisões Pb-Pb a $\\sqrt = 2.76$ TeV e em colisões Au-Au a $\\sqrt = 200$ GeV. / This work is dedicated to the study of the photoproduction of vector mesons in ultra-peripheral collisions. This study was accomplished by means of the Monte Carlo code CRISP which gained updates and implementations in order to allow the calculation of the collisions. A model for the generation of the spectrum of equivalent photons that interact with the target was designed. Also, new photo-absorption channels for the multipion photoproduction were introduced in the code. They are essential to the description of the nuclear environment at high energies. Altoghether, 84 channels were implemented. In particular, the production of the J/$\\psi$ vector meson in Pb-Pb collision at $\\sqrt = 2.76$ TeV and in Au-Au collisions at $\\sqrt = 200$ GeV was studied.

Thesis (M.S.)--Mississippi State University. Department of Physics and Astronomy. / Title from title screen. Includes bibliographical references.

Este trabalho é dedicado ao estudo da fotoprodução de mésons vetoriais em colisões ultra-periféricas. Este estudo foi realizado por meio do código de Monte Carlo CRISP, o qual recebeu atualizações e implementações a fim de permitir o cálculo das colisões. Foi elaborado um modelo para a geração do espectro de energia dos fótons equivalentes que deve interagir com o alvo, bem como foram introduzidos novos canais de foto-absorção para a fotoprodução de múltiplos píons, os quais são essenciais à reprodução dos fenômenos nucleares em altas energias. Ao todo 84 canais foram introduzidos. Foi estudada, em particular, a produção do méson J/$\\psi$ em colisões Pb-Pb a $\\sqrt = 2.76$ TeV e em colisões Au-Au a $\\sqrt = 200$ GeV. / This work is dedicated to the study of the photoproduction of vector mesons in ultra-peripheral collisions. This study was accomplished by means of the Monte Carlo code CRISP which gained updates and implementations in order to allow the calculation of the collisions. A model for the generation of the spectrum of equivalent photons that interact with the target was designed. Also, new photo-absorption channels for the multipion photoproduction were introduced in the code. They are essential to the description of the nuclear environment at high energies. Altoghether, 84 channels were implemented. In particular, the production of the J/$\\psi$ vector meson in Pb-Pb collision at $\\sqrt = 2.76$ TeV and in Au-Au collisions at $\\sqrt = 200$ GeV was studied.