NUCLEAR REACTION AND DISPERSION

Author: Ricciardi Maria Valentina.
Year: 2004.
University: SANTIAGO DE COMPOSTELA [www.usc.es].
Place of defense: Universidad de Santiago de Compostela.
Place of preparation: Universidade de Santiago de Compostela.

Summary: The experimental technique has been used very precise measurements of the isotopic composition and timing of longitudinal all residual nuclei produced in these reactions with a value of the atomic number between 7 and 37. This has been used espectómetro magnetic FRS of GSI. These measures have led to four key results:-It has been revealed the existence of an effect par-impar in the isotopic distribution of light nuclei produced in the reaction 238U (1 A GeV) + Ti. This effect has been explained on the basis of the statistical model desexcitacíon nuclear includes a transicíon between the nuclear apareada (superfluída) and the nuclear field where nucleons are not matched. The isotopic distributions and velocities of light waste produced in the reaccíon 238U (1 A GeV) + p indicate that the mechanism reaccíon dominant is fission. Therefore, the energy induced in this reaccíon is not enough to induce a process of multifragmentación which is interpreted as a transitional phase between the nuclear field and matter hadrónica. - The observed excess neutrons in the nuclei residual light produced in the reaction 238U (1 A GeV) + Ti has been interpreted as a result of a glut in the temperature reached in this reaction that corresponds to the image of multifragmentación nuclear and therefore the transition phase between the nuclear field and matter hadrónica. - The speed of light nuclei produced in the reaction 238U (1 A GeV) + Ti show an acceleration that has been interpreted as the response of the nucleus spectator to the explosion of the participant. This observation is evidence of dependence on nuclear field half the time.

Author: ALBERTUS TORRES CONRADO.
Year: 2005.
University: GRANADA [www.ugr.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS - UNIVERSIDAD DE GRANADA.

Summary: This thesis has developed a variational method for studying the properties of the ground state systems hadrónicos three bodies. We have incorporated key ingredients and dynamic symmetries paroximadas which facilitate the treatment of these problems. Among the results of this work are: We have shown that by including half a correction is possible to describe the experimental masses of hipernúcleos Lambda-Lambda. The series RPA has allowed us to deduce a potential Lambda-Lambda cash, built from an interaction type Bonn-JÃ ¼ lich adjusted data dissemination barión-barión in free space, taking into account uncertainties theoretical and experimental, describes the masses of hipernúcleos double Lambada of I, and be bo. It has conducted a study of the disintegration piónica of hipernúcleos Lambda. It has improved the description of certain details of the underlying nuclear structure in the process, and we have also implemented a layered model in continuing to describe the contributions which the nucleon of the disintegration of hiperón Lambda, it is not caught by the residual core. It has developed a variational scheme to study the spectrum and some static properties of baryons that contain a quark co b. We have calculated masses and wave functions from variational principle applied to a family of Jastrow type functions, which are designed from restrictions symmetry quqrk heavy (HQS) to the dominant order. Thanks to HQS wave functions are simpler and more manageable than those achieved by solving the equations of Fadeev, are easy to use in other contexts, to be easily parameterized. We have identified significant shortcomings of the studies of the decay semileptónicas of baryons Lambda-by Xi-b model-based non-relativistic quark constituents. We have provided solutions to these problems, and so we have imposed relations between the form factors offset by HQS, and proposed a new development of electroweak current operator, retaining all orders soon transferred. This analysis leads to a joint reliable and accurate description of the form factors in the collapse semileptónica of baryons Lambda-by Xi-be. We have identified the role of Isgur-Wise corrected in terms of order 1/mQ, which governs these processes and, given the value of parameters Vcb. We have also calculated asymmetry parameters that determine the angular distribution of disintegration. We have highlighted the limitations of a valence quark model to describe the decay semileptónicas B-largest pi, D-and D-largest pi major K. As a first correction we have included in each case, the contribution of resonance pole vector heavy -- slightly closer to q2 maximum. We also deducted a dispersion type Omnés for f + multi subtractions, which significantly reduces dependence on the results of the behavior of the scattering amplitudes of elastic B-pi high energies. Using this representation Omnés we calculate the form factor f + wide range of values explored in greater disintegration B-pi, can thus evaluate the overall width. It was also estimated the theoretical uncertainties that affect all our predictions, and in particular we found Vub = 0.0034 + / -0.0003 (Exp.) + / -0.0007 (Teo.), in good agreement with the determination of the experimental collaboration Cleopatra . In the case of the decay semileptónicas D-largest largest D-K and pi our results for f +, which includes the contribution of valence quarks and the pole of the resonances D * D * s, are in good agreement with those of the collaboration Fermilab-MILC-HPQCD obtained from a simulation of the lattice QCD with three flavors dynamic.

Author: FERNÁNDEZ RAMÍREZ CÉSAR.
Year: 2005.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: UNIVERSIDAD COMPLUTENSE DE MADRID.

Summary: Although the Cromodinámica Quantum (QCD) is regarded as the correct theory of the strong interaction, in the range of energies of the nucleon and the resonances nucleónicas approach perturbativo inherent in QCD is not adequate. So it has to rely on an effective approach if we are interested to know the properties of resonances nucleónicas and the process in which they are involved, principally production Inns, which is the dominant channel. In this thesis develops a model of totoproducción of piones in free nucleons, which has been proven as the best mechanisms for the study of the nucleon and its resonances and to study the role of pión and resonances in the nuclei . The model fotoproducción is based on an approach to lagrangianos troops that includes seven resonances nucleónicas addition to the terms of Born and exchange Inns vector. The model incorporates a modern treatment of the resonances of spín 3 / 2 that prevents diseases present in previous models. Other important features of the model are chiral symmetry, invariance and gauge symmetry exchange. I use the model combined with modern techniques of optimization based on genetic algorithms to establish the parameters of the resonances based on the global database of multipolos electromagnetic. The thesis presents results for multipolos electromagnetic effective differential sections, asymmetries and totals for all sections efficient production processes of a pió of nucleons free. It gets a good global adjustment from the threshold to 1 GeV energy in the system's reference laboratory.

Author: DÒ¶ring Michael Ulrich.
Year: 2006.
University: VALENCIA [www.uv.es].
Place of defense: Facultad de Física.
Place of preparation: Universidad de Valencia.

Summary: The description of theoretical physics hadrónica to low and intermediate energy continues to pose a major challenge. The richness of the phenomenology is reflected in the large number of resonances in the sectors mesón-mesón and mesón-barión. Arrojar new light on specific issues in this field is the objective of this thesis. The chiral unitary theory (UChPT) allows extend chiral perturbation theory (ChPT) at higher energies using techniques that meet the unitaridad exact channels trailers and matches the results of ChPT at low energies. We studied the interaction pión-nucleón in the doorway and near the same. In this context the unitarización the amplitude pión-nucleón is interesting because it generates diagrams multiple collision in which the interaction isovector repeatedly leads to a contribution isoscalar. The novelty of this study is the consideration of those terms of higher orders and their impact near the doorway. To isolate this effect must perform work nothing trivial in relation to the problem of collisions of three bodies in deuterium piónico. In a global adjustment we have to consider all the data and get a good description of the threshold to intermediate energies. With that precise amplitude at our disposal, we apply the model in the context of the "lack of revulsion." The model of vacuum previously served input for the calculation of the means of nuclear weapons. In the following studies we deal with applications more genuine UChPT. Following the unitarización appear poles at the complex energy invariant collision. It is clear that higher energy, the resonances performance an important role. To study the structure of the mechanisms of taste gamma p --> pi pi N, the problem should be addressed with an open mind, in other words, we should take into consideration the production of two inns that are not necessarily piones. Thanks to the theoretical progress in that direction, we now have the requesitos required for a realistic model: many resonances are described as either dynamically generated and under formalism coupled channel can be predicir many links in SU (3). In meritadas reactions N (1535) occupies a prominent role, however, as the main source of contribution, identify another resonance also considers dynamically generated, the Delta (1700) and their furtes links to channel eta-Delta (1232 ) and KSigma (1385). As we have found the Delta (1700) of special relevance, studying in almost a dozen different reactions induced by photons and piones. Sections effective different reactions can be distinguished among them case by two orders of magnitude. However, the model provides a good description for all global reactions without introducing new parameters. That supports the theory that the Delta (1700) is generated dynamically. So after studying the fotoproducción two inns, it is necessary to investigate resonances dynamically generated by radiative decay. We focus on the same radiative decay of the Lambda (1520). We show that the radiative decay can be used to facilitate understanding of the mixture of dynamically generated part of the wave function and the small part genuine. Including the channel pión-nucleón wave d, calculate the radiative decay of the Delta (1700) and we found good agreement with the disintegration radiative abservada, which amounts to corroborate the Delta (1700) as resonance dynamically generated. The reduction of load fluctuations due to the breaking load quarks in the Quark-Gluon-Plasma (QGP), could demonstrate that QGP. In this thesis the interaction is given by the exchange of rho inn. Fluctuations load is calculated by autoenergía of photon up to the level of two loops. We demonstrate explicitly conservation burden in this method. We also former 8 tended 317 formalism development virial to include statistics correctly states asintóticos the collision.