Thèses sur le sujet « Mesens »

Two decay channels of the ω(782) meson, into π+π-π0 and π+π-, are studied. The dynamics of the three-pion channel is represented using a two-dimensional distribution, called a Dalitz plot. A high-statistics Dalitz plot distribution is needed to test theoretical predictions and increase understanding of the decay mechanism. The isospin-breaking two-pion decay gives insight into the ρ-ω mixing. The ω→π+π- decay has previously been studied in π+π- spectra in high statistics e+e- experiments and with lower statistics in hadroproduction experiments. The collected evidence indicates that the resulting interference pattern strongly depends on the production reaction. In 2011 an experiment to investigate ω hadronic decays in pd→3Heω reaction was performed with the WASA detector. Two studies based on the collected data are included in this thesis. In the first, the dominant decay channel ω→π+π-π0 is selected and two experimental Dalitz plot distributions are created. Each distribution corresponds to one of the two incident beam energies used in the experiment. A fit to the Dalitz plots is performed using a parametrisation including the expected P-wave shape. The result indicates an onset of the intermediate ρ in the two-pion channel, as predicted by theoretical models. The efficiency corrected Dalitz plot bin contents are reported to facilitate comparison to theoretical predictions by direct fits to the experimental data. In the second study, the ω→π+π- decay channel is selected. For events with a 3Heπ+π- final state, the 3He missing mass is constructed in search for the ρ-ω interference pattern in pd production. No significant deviations around the ω mass position was found. Dedicated studies using experimental data to estimate background contribution and to extract signal acceptance shows that the background is too large to observe the expected signal with the collected data sample. The last part of the thesis presents pre-studies for using data collected at the KLOE detector for an ω→π+π-π0 Dalitz plot analysis. Since the ω mesons are produced in the e+e-→ωπ0 reaction, the study focuses on the impact of the π0-π0 interference.

The mechanism of the isospin violating η→π+π−π0 decay is studied in a high precision experiment using a Dalitz plot analysis. The process is sensitive to the difference between up and down quark masses. The measurement provides an important input for the determination of the light quark masses and for the theoretical description of the low energy strong interactions. The measurement was carried out between 2004 and 2005 using the KLOE detector at the DAΦNE e+e− collider located in Frascati, Italy. The data was collected at a center of mass energy corresponding to the φ-meson peak (1019.5 MeV) with an integrated luminosity of 1.6 fb−1. The source of the η-mesons is the radiative decay of the φ-meson: e+e−→φ→ηγ, resulting in the world’s largest data sample of about 4.7·106 η→π+π−π0 decay events. In this thesis, the KLOE Monte Carlo simulation and reconstruction programs are used to optimize the background rejection cuts and to evaluate the signal efficiency. The background contamination in the final data sample is below 1%. The data sample is used to construct the Dalitz plot distribution in the normalized dimensionless variables X and Y. The distribution is parametrized by determining the coefficients of the third order polynomial in the X and Y variables (so called Dalitz plot parameters). The statistical accuracy of the extracted parameters is two times better than any of the previous measurements. In particular the contribution of the X2Y term is found to be different from zero with a significance of approximately 3σ. The systematic effects are studied and found to be of the same size as the statistical uncertainty. The contribution of the terms related to charge conjugation violation (odd powers of the X variable) and the measured charge asymmetries are consistent with zero. The background subtracted and acceptance corrected bin contents of the Dalitz plot distribution are provided to facilitate direct comparison with other experiments and with theoretical calculations.

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.

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xiii, 131 p.; also includes graphics. Includes bibliographical references (p. 128-131). Available online via OhioLINK's ETD Center

Al llarg dels últims anys, s'han observat nombroses senyals que suggereixen l'existència de Física més enllà del Model Estàndard en desintegracions semi-leptòniques de mesons B, mediades per transicions del tipus b --> sll. Més concretament, l'experiment LHCb, juntament amb altres experiments al LHC i col·laboracions externes com Belle, han trobat desviacions en les mesures experimentals de diferents observables d'important rellevància respecte les seves prediccions teòriques en el Model Estàndard. Parcialment, aquesta situació no es sorprenent, ja que en un conjunt gran de dades un sempre espera tenir un subconjunt en tensió amb les seves prediccions. No obstant, la importància de les observacions actuals és que totes aquestes tensions formen un patró coherent apuntant cap a "una direcció privilegiada". Per aquesta raó, els anàlisis globals d'aquestes dades mostren una discrepància general de més de 5sigmes respecte el Model Estàndard Per estudiar aquestes tensions de manera consistent, treballem des del marc del Hamiltonià efectiu que descriu la dinàmica de les transicions b --> sll. Aquesta descripció, conceptualment senzilla, ens permet descriure qualsevol desintegració d'un mesó B, que procedeixi a través de l'anterior transició, en base a un conjunt reduït de paràmetres. Precisament, aquest fet és el fa possible analitzar la totalitat dels observables on s'observen tensions de manera eficient per mitjà de fits globals. En aquesta Tesi, presentem la última versió dels anàlisis globals esmentats. Primer, descrivim el context teòric general que ens serveix de base per tots els nostres càlculs, fent especial èmfasi en l'estimació dels errors corresponents. I després, exposem els nostres resultats amb tota profunditat de detalls, així com comentem també les seves possibles implicacions.
Recientemente, el campo de las desintegraciones electro-débiles de mesones B ha observado la aparición de numerosas señales que indican la existencia de Física más allá del Modelo Estándar, siendo los procesos mediados por transiciones b --> sll el contexto habitual de dichas señales. Más en detalle, el experimento LHCb, junto con otros de los experimentos en el LHC y otras colaboraciones como Belle, han encontrado desviaciones en los valores experimentales de distintos observables, relevantes en la caracterización de las transiciones b --> sll, con respecto sus predicciones teóricas en el marco del Modelo Estándar. En parte, esta situación no es sorprendente, puesto que uno se espera encontrar varias medidas en tensión con sus predicciones en un conjunto grande de datos. No obstante, lo que es muy destacable es que estas tensiones forman un patrón de desviaciones con coherencia interna y parece que apuntan todas "en la misma dirección". Por esta razón, al evaluar la importancia global del conjunto de tensiones mediante un análisis global, el resultado indica una discrepancia general de los datos con respecto del Modelo Estándar de más de 5sigmas. Para estudiar dichas tensiones de forma consistente utilizamos un Hamiltoniano efectivo, dónde se codifica la dinámica de las transiciones b --> sll. Esta simple herramienta nos permite describir cualquier desintegración de un mesón B, que opere a través de dicha transición, a través de un conjunto reducido de parámetros, hecho que posibilita poder analizar un conjunto numeroso de datos por medio de fits globales. En esta Tesis presentamos la última versión de los citados análisis globales. Primero, describimos el contexto teórico general que sirve de base para todos nuestros cálculos, prestando especial atención a los métodos utilizados para estimar la incertidumbre asociada a nuestras predicciones, para después mostrar todos los detalles de nuestro análisis así como sus implicaciones.
In the recent years, intriguing hints of New Physics (NP) have been accumulated in semileptonic B-meson decays, mostly involving neutral-current transitions b --> sll. The LHCb collaboration, other collaborations at the LHC and the Belle experiment have reported deviations from the Standard Model expectations in several observables measuring the aforementioned transition. These are commonly referred to in the literature as B-anomalies. Not surprisingly, some of these measurements show deviations from the SM predictions by a few standard deviations. More interesting is the fact that several of these deviations from the SM appear to be "in the same direction", in such a way that when quantified by a global fit the discrepancy with the SM is over the 5sigma level. In order to assess the significance of these anomalies and to treat them consistently, we propose a model-independent analysis based on an Effective Hamiltonian encoding the dynamics of the underlying quark level transition. This has the advantage of providing a simple systematic framework where all possible processes, mediated by the same transition, can be described with the same set of parameters, allowing for global fits of large numbers of observables defined in several channels. This Thesis presents our most updated global analyses of b --> sll data. First, we describe the general framework used to compute the different types of observables, paying special attention to the treatment of the uncertainties involved. And then, we discuss both our analytical approach and the implications of the most significant results obtained from our fits.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.
Includes bibliographical references (leaf 22).
We present the P-matrix, an alternative method to parameterize the S-matrix, which is particularly useful for low energy meson-meson scattering. We discuss its basic properties and use it to analyze the isospin 0 and 2 s-wave [pi] [pi] scattering. We construct the S-matrix from our analysis and discuss the physical relevance of its poles. Further details of P for more general cases are provided in the appendices.
by Fethi̇ Mübi̇n Ramazanoğlu.
S.B.

The purpose of this thesis has been to study the S=-1 meson-baryon interaction in S-wave employing an effective chiral SU(3) lagrangian up to NLO and implementing unitarization in coupled channels. Such a study requires fixing the NLO coefficients of the lagrangian which are not well established yet. In general, the low energy constants of an effective lagrangian are obtained from fitting procedures to the experimental available data. These parameters have been constrained to a large set of experimental K^- p scattering data into πΣ,K ̅N, πΛ channels, to γ, R_n and R_c branching ratios, and to the precise SIDDHARTA value of the energy shift and width of kaonic hydrogen. The novelty of our work is the inclusion of the scattering data from K^- p⟶K^+ Ξ^-,K^0 Ξ^0 reactions in the fitting procedure, since they become especially sensitive to higher order terms, as they cannot proceed with the WT term of the lagrangian, except indirectly via unitarization contributions. We have paid a special attention to the effects that a systematic inclusion in the lagrangian of the NLO and Born terms has on the low energy constants, particularly on the NLO coefficients. The main difference among the models we get from the fits is reflected in the isospin components of the total cross sections of the reactions we study. To check the reliavility of these models, we have performed new fits which take into account data from isospin filtering reactions. The stability and accuracy of the parameters have been tested by including phenomenological resonant contributions to the scattering amplitudes of the reactions that are especially sensitive to the NLO corrections. These resonant terms have been useful to reach better agreement with the experimental data. In order to explore other processes that take place at higher energies and can provide more information of the NLO parameters, we have studied the Λ_b decay into states containing a J/ψ and meson-baryon pairs. Furthermore, the Λ_b⟶J/ψ ηΛ process has allowed us to study the implications of observing a possible strange partner of the hidden charm pentaquark state P_c (4450). The conclusions and analysis of each chapter are summarized below. The second chapter is devoted to study the role played by NLO and Born terms, as well as the relevance of certain reactions in obtaining a more reliable parametrization for the NLO coefficients. We started by comparing different fitting procedures consisting of unitarized calculations employing a kernel in which we include or not the NLO term and which take into account or not the scattering data of the K^- p⟶KΞ reactions. From the results of all these combinations, and particularly from the successful reproduction of the experimental data reached by the WT+NLO model, we have shown for the first time that the NLO order terms of the chiral Lagrangian are absolutely necessary to reproduce the K^- p⟶KΞ reaction data. In this way, the sensitivity of the NLO lagrangian to such reactions has been clearly established. Given this sensitivity and the fact that the existing K^- p⟶KΞ scattering data are limited and suffer from large uncertainty, more accurate data are required before giving a more definitive answer about the values of the NLO coefficients. Next, contrary to the assumption we made about the little effect of the Born terms in the earlier stage, we have proved that they become non-negligible in the K^- p⟶KΞ reactions. The parametrization of the new fit (WT+NLO+Born) has confirmed the expectations of obtaining significant changes in the NLO coefficients compared to those of the WT+NLO model. Despite this, we do not get any improvement neither in accuracy of the parameters nor in the χ_(d.o.f)^2. This fact has led us to an interesting finding that allows us to understand how such different parametrization could give so similar agreement with the experimental data: the inclusion or non inclusion of the Born terms can seriously modify the isospin decomposition of the K^- p⟶KΞ cross sections due to their sensitivity to the higher order terms. Such differences in the isospin components point to the need of constraining the models with experimental data from reactions that proceed through I=0 or I=1, thus providing more reliable parameters of the meson-baryon lagrangian. Most of the data employed in our fits are coming from antikaon-proton scattering and therefore contain contributions from both isospin I=0 and I=1 components; being the only exceptions the π^0 Σ^0,πΛ channels, which select I=0 and I=1 respectively. We then have widened the number of experimental observables used in the fits including scattering data from K^- p⟶ηΛ,ηΣ^0 reactions, which are of pure isospin 0 and 1 respectively. These efforts culminated in the WT+NLO+Born (η chan) model that, as far as we know, is the only chiral model in the literature which reproduces K^- p scattering data into all possible S=-1 channels with good agreement. Regarding the parametrization related to this model, the inclusion of these new experimental data has been crucial for obtaining a very homogeneous and accurate set of NLO coefficients, as well as natural sized values for all the subtraction constants. This leads us to think that the inclusion of more experimental data from isospin filtering processes could favor more reliable values for the low energy constants. The proposed measurement of the K_L^0 p⟶K^+ Ξ^0 reactions in I=1 with a secondary K_L^0 beam at Jlab would complement the information one can obtain from K^- p scattering data to constrain the theoretical models. We have presented our prediction for this reaction employing some of our models, concluding that, as more contributions are taken into account in the interaction kernel and more data are included in the fit, the predicted values are closer to the only two available experimental points of this reaction. None of these two data points have been used in any fitting procedure. This prediction seems to point out towards the reliability of our parametrizations, particularly the WT+NLO+Born (η chan) one, which we consider our best pure chiral model. In order to improve the description of the experimental K^- p⟶KΞ and K^- p⟶ηΛ scattering data, it is also possible to considerate the inclusion of high-spin resonances in such processes. Since they are the most sensitive reactions to the NLO terms, this could also lead to modifications of the NLO parameters. In this way, we can study the stability and accuracy of the parameters present in the models. This is performed in the third chapter of this thesis. We first allowed for the explicit contribution of the high spin hyperon resonances Σ(2030) and Σ(2250) to the K^- p⟶KΞ amplitudes, aiming at establishing an appropriate amount for the background, which in this work is associated to the chiral contributions, and, hence, obtaining more reliable values of the associated low energy constants. The resonant amplitude has been calculated by applying the Rarita-Schwinger method while the chiral amplitude has been obtained employing a lagrangian with a WT and NLO contribution giving rise to the NLO+RES model. Since the resonant terms introduce an angular dependence in the amplitudes, we also attempt the description of the KΞ differential cross sections. We find the resonant terms to have a double benefit. On the one hand, they allow for a reasonable overall description of the scattering data, including the total and the differential cross sections of the KΞ production reactions. On the other hand, by absorbing certain structures of the cross section, the inclusion of resonant contributions permit finding a more stable solution and therefore more precise values of the low energy constants of the chiral unitary model. Then, we have performed a similar study for WT+NLO+Born (η chan) model, which we consider our best chiral model. In contrast to the study carried out previously, this model has been constrained with additional data (K^- p⟶ηΣ^0,ηΛ cross-section data), meaning that, since the K^- p⟶ηΛ reaction is also very senstive to the NLO terms, the corresponding NLO coefficients are more reliable. This makes the analysis of stability acquire a more decisive character. Aiming for this, we have extended the resonant contributions to the K^- p⟶ηΛ process, particularly we have taken into account the contribution of the Λ(1890) resonance which has also been incorporated to the K^- p⟶KΞ amplitudes, in addition to the Σ(2030) and Σ(2250) resonances. The results obtained confirm the previous findings: there is a notable improvement of the agreement with the experimental data and the parameters take similar values to the ones corresponding to the model without resonances. This stability is specially marked for most of the NLO coefficients. Having proved the effects of the isospin filtering processes on the NLO coefficients, in Chapter 4 we have shown that the Λ_b⟶J/ψ ηΛ decay and, particularly, the Λ_b⟶J/ψ KΞ one provide very valuable information concerning the meson-baryon interaction in the S=-1 and isospin I=0 sector. The dynamics of the reaction, where the light quarks of the Λ_b play a spectator role, is such that it filters I=0 in the final state. This is so because the "u" and "d" quarks in the Λ_b baryon necessarily couple to I=0 and the weak decay favors the b⟶cc ̅s transition, so there is an s-quark at the end of the weak process, which together with the "ud" pair in I=0 gives a total isospin I=0. Thus, these decays may offer complementary information to that obtained from K^- p⟶KΞ scattering data, where both isospin 0 and 1 contributions combine to give the final results. Our study is based on the models WT+NLO (Model 1) and WT+NLO+Born (η chan) (Model 2) developed in this thesis to describe the K^- p scattering. Both models produce quite different invariant mass distributions for the decay of the Λ_b into KΞ and ηΛ states, which are in turn quite different also from phase space, indicating the sensitivity of these processes to the strong internal dynamics. The differences between models are more visible in the Λ_b⟶J/ψ KΞ decay process. The reason stems from the fact that the decay into ηΛ can proceed at tree level, while the selectivity of the Λ_b decay processes producing the J/ψ does not allow the formation of a KΞ pair in a primary step. This is only produced through rescattering of the K ̅N and ηΛ primary components. Thus the Λ_b⟶J/ψ KΞ reaction is directly proportional to the meson-baryon scattering amplitude, concretely to the ηΛ⟶KΞ and K ̅N⟶KΞ components in I=0, which can lead to a marked pattern of interferences. These models also predict sizable differences for the Λ_b decay in the energy region of KΞ and ηΛ production, reflecting that the I=0 component of the meson-baryon interaction, which is the one playing a role in the Λ_b decay processes studied here, is not very well constrained by the fitting to K^- p⟶KΞ data. The recent finding of two structures in the J/ψ p invariant mass distribution of the Λ_b⟶J/ψ K^- p decay, associated to two pentaquark states, together with its plausible explanation in terms of a previously predicted hidden charm baryon molecular state, prompted us to study the decay of the Λ_b into J/ψ ηΛ final states. The Λ_b⟶J/ψ ηΛ decay, being a coupled channel of the Λ_b⟶J/ψ K^- p one, will occur with similar strength and one could observe, in the J/ψ Λ invariant mass spectrum, possible strange partners of the two non-strange pentaquark states reported by LHCb collaboration. We recall that when the hidden charm N^* resonances were theoretically predicted as molecular states in several unitary approaches, some partner hidden charm strange Λ^* states were also found. We have taken advantage of this finding and have predicted what signal should one of these states leave in the ηΛ and J/ψ Λ invariant mass distributions of the Λ_b⟶J/ψ ηΛ reaction. We have found that, taking the values of the couplings of the hidden charm Λ^* state to the D ̅^(0*) Ξ_c^' and J/ψ Λ channels obtained in the unitary approaches, one should observe clear and sizable peaks in the J/ψ Λ mass distribution of the Λ_b⟶J/ψ ηΛ decay. We have studied the dependence of our results on reasonable changes in the parameters of the models involved in our description of the process, as well as on the unknown properties of the speculated hidden charm strange pentaquark. We have observed that, while there appear changes in the position of the peak and in the shapes of the distributions, a resonance signal in the J/ψ Λ invariant mass spectrum is clearly seen in all the cases. This gives us confidence that such an experiment should result into a successful proof of the existence of this new state and we encourage the experimental analysis of this decay channel, for which our theoretical study predicts a similar strength than for the Λ_b⟶J/ψ K^- p reaction already analyzed by LHCb. The present work is our first step toward building a more complete chiral model in S=-1 sector to help analyze the forthcoming more precise data in the KΞ production. In addition, the findings and the features observed in this study indicate that the actual measurement of the complementary observables analyzed here would provide valuable information, novel so far, that would enrich our knowledge of the meson-baryon interaction and help us make progress in our understanding of hadron dynamics.
En esta tesis se ha estudiado la interacción mesón-barión en onda S en el sector de extrañeza -1 empleando un lagrangiano de SU(3) hasta segundo orden, implementando la unitarización en canales acoplados. La condición indispensable para llevar a cabo un estudio de este tipo, forzosamente, pasa por fijar el valor de los coeficientes presentes en los términos de segundo orden, los cuales no poseen un valor bien determinado. Generalmente, las constantes de baja energía de los lagrangianos efectivos se obtienen mediante procesos de ajuste a los datos experimentales disponibles. Tradicionalmente, en este sector de extrañeza, dichos parámetros se ajustaban a los datos experimentales de la dispersión K^- p a los canales πΣ, K ̅N, πΛ, así como a las razones entre secciones eficaces en el umbral de producción K^- p: γ, R_n y R_c; y a los precisos valores del corrimiento y la anchura parcial del estado 1s del hidrógeno kaónico obtenido por la colaboración SIDDHARTA. Lo novedoso en nuestra tesis es la inclusión de datos experimentales procedentes de la reacción de dispersión K^- p⟶K^+ Ξ^-,K^0 Ξ^0 en los procesos de ajuste. La motivación para ello se debe a la especial sensibilidad de estas reacciones a los términos de órdenes superiores, ya que estas reacciones no proceden de manera directa mediante el término WT que es el dominante a primer orden. A esto se le suma el hecho que las contribuciones que provienen de la redispersión de los canales acoplados no son capaces de reproducir adecuadamente los datos experimentales. Dado lo anterior, nos centramos en estudiar los efectos producidos por la inclusión sistemática en el lagrangiano de los términos de segundo orden ("NLO") y los de Born sobre las constantes de baja energía, particularmente sobre los coeficientes de "NLO". La principal diferencia entre los modelos que se obtienen de los ajustes se refleja en las componentes de isospín de la sección eficaz total de las reacciones que aquí se estudian. Así pues, para comprobar la fiabilidad de estos modelos, se llevaron a cabo nuevos ajustes teniendo en cuenta datos experimentales procedentes de reacciones de filtrado de isospín. Adicionalmente, se han estudiado la estabilidad y la precisión de los parámetros obtenidos de los ajustes añadiendo contribuciones resonantes de manera fenomenológica a aquellas amplitudes de dispersión asociadas a las reacciones que son especialmente sensibles a las correcciones de segundo orden. Debe destacarse que las contribuciones resonantes han proporcionado una mejora del acuerdo entre los modelos teóricos y los datos experimentales. La desintegración de Λ_b dando lugar a estados que contienen una partícula J/ψ junto con un par mesón-barión resulta ser un proceso muy interesante para extraer información sobre los parámetros de "NLO" a energías más altas. Además, el proceso Λ_b⟶J/ψ ηΛ nos ha permitido estudiar las implicaciones que tendría la posible existencia de un homólogo extraño del pentaquark con encanto escondido P_c (4450). Las conclusiones y el análisis de cada capítulo están descritos en los párrafos siguientes. El Capítulo 2 está dedicado al estudio del papel que juegan los términos de "NLO" y los de Born, así como la relevancia de ciertas reacciones para obtener parametrizaciones más fiables de los coeficientes de "NLO". Al principio, comparamos diferentes ajustes que se basaban en cálculos unitarizados empleando núcleos de interacción que incluían o no los términos de "NLO" y para los cuales se tenían en cuenta o no los datos experimentales de la reacción de dispersión K^- p⟶KΞ. Fruto de los resultados obtenidos de todas estas posibles combinaciones, y más particularmente de la excelente reproducción de los datos experimentales lograda por el modelo WT+NLO, se mostró por vez primera que los términos de "NLO" del lagrangiano quiral son absolutamente necesarios para reproducir los datos experimentales de las reacciones K^- p⟶KΞ. De este modo, se evidenció la sensibilidad del segundo orden del lagrangiano a dichas reacciones. Dada esta sensibilidad junto con el hecho que los datos existentes de la reacción de dispersión K^- p⟶KΞ son limitados y que tienen asociada una gran incertidumbre, para poder dar una respuesta definitiva sobre los valores de los parámetros de "NLO" se requerirían datos experimentales más precisos. Después, contrariamente a lo que se asumió a cerca del efecto negligible de los términos de Born, demostramos que estas contribuciones no pueden menospreciarse en las reacciones K^- p⟶KΞ. Las significativas diferencias en los coeficientes de "NLO" entre la nueva parametrización obtenida para el modelo WT+NLO+Born y la que se obtuvo para el modelo WT+NLO confirmaron el hecho anterior. A pesar de esto, no se apreció ninguna mejora en la precisión de los parámetros ni en el χ_(d.o.f)^2. Este resultado nos permitió entender cómo dos parametrizaciones tan diferentes pueden tener una bondad del ajuste tan similar: la inclusión o no de los términos de Born puede modificar notablemente la descomposición en componentes de isospín de la sección eficaz total de la reacción K^- p⟶KΞ debido a su sensibilidad a los términos de orden superior. Tales diferencias entre las componentes de isospín nos llevan a pensar que si nuestros modelos se ajustan a datos experimentales procedentes de reacciones que actúan como selectores de isospín podremos extraer valores más realistas para los parámetros presentes en el lagrangiano. La mayoría de los datos experimentales empleados en nuestros ajustes vienen de la dispersión protón-antikaón y, consecuentemente, contienen contribuciones tanto de componentes de isospín I=0 como de I=1 siendo las únicas excepciones los canales π^0 Σ^0,πΛ, que filtra isospín 0 y 1 respectivamente. Así pues, se decidió ampliar el número de observables empleados en los ajustes añadiendo datos experimentales de las reacciones de dispersión K^- p⟶ηΛ,ηΣ^0, las cuales tienen solamente una única componente de isospín para sus secciones eficaces, i. e., isospín 0 y 1 respectivamente. Todos estos esfuerzos culminaron con la obtención del modelo WT+NLO+Born (η chan) que, hasta donde sabemos, es el único capaz de reproducir razonablemente bien los datos de la dispersión K^- p a todos los posibles canales del sector S=-1. Respecto a los parámetros de este modelo, se puede destacar el papel relevante de estos nuevos datos experimentales a la hora de obtener unos valores muy homogéneos y precisos para las constantes de "NLO" junto con unas constantes de substracción cuyos valores se acercan más a los valores naturales. A la vista de estos resultados, la inclusión en los ajustes de nuevas reacciones donde se filtre el isospín podría favorecer la obtención de valores más realistas para las constantes de baja energía. La propuesta para medir la reacción K_L^0 p⟶K^+ Ξ^0 en I=1 empleando el haz secundario de K_L^0 en Jlab podría suponer una fuente de información complementaria a la dispersión K^- p. Se ha presentado una predicción para esta reacción empleando algunos de nuestros modelos de la cual se concluye que, cuantas más contribuciones se tienen en cuenta en el núcleo de interacción y más datos experimentales se incluyen en los ajustes, más cerca estamos de reproducir los dos únicos puntos disponibles para esta reacción. Hay que remarcar que ninguno de estos puntos se ha utilizado en los ajustes. A la luz de estos resultados, parece que nuestros parámetros toman cada vez valores más confiables, particularmente los del modelo WT+NLO+Born (η chan), al cual consideramos nuestro mejor modelo quiral puro. Con la intención de mejorar la descripción de los datos experimentales de las reacciones K^- p⟶KΞ y K^- p⟶ηΛ, se incluyeron resonancias de spin alto en estos procesos. Como estas reacciones son las más sensibles a los términos de "NLO", este hecho podría inducir modificaciones en los valores de los coeficientes de "NLO". De este modo, podemos estudiar la estabilidad y precisión de los parámetros presentes en los modelos. Este estudio se llevó a cabo en el Capítulo 3. La primera parte de este estudio consistió en la inclusión explícita de los hyperones de spin alto Σ(2030) y Σ(2250) en la amplitud de dispersión K^- p⟶KΞ, con la intención de fijar una contribución quiral con la cual los términos resonantes puedan interferir para reproducir adecuadamente las estructuras mostradas por los datos experimentales sin tener que forzar a los parámetros de "NLO" a tomar valores sobrestimados. Para calcular la amplitud resonante, hemos utilizado el método de Rarita-Schwinger, mientras que la amplitud quiral se ha calculado empleando un lagrangiano con los términos WT y NLO dando lugar a un nuevo modelo, NLO+RES. Como los términos resonantes introducen una dependencia angular en las amplitudes, se decidió aprovechar este hecho para reproducir los datos experimentales de la sección eficaz diferencial con un acuerdo razonable dadas las limitaciones del modelo para ello. De aquí se puede concluir que la inclusión de términos resonantes cumple una doble función. Por un lado, nos permite obtener una mejora global en la descripción de los datos de dispersión, tanto los de las secciones eficaces totales como los de las diferenciales en las reacciones de producción KΞ. Por otro lado, absorbiendo ciertas estructuras de las secciones eficaces, la inclusión de términos resonantes permite encontrar mínimos más estables y, por consiguiente, valores más precisos de las constantes de baja energía del modelo quiral unitario. Seguidamente, realizamos un estudio similar para el modelo WT+NLO+Born (η chan). Comparado con el anterior, este modelo ha sido ajustado a datos experimentales adicionales (datos de las secciones eficaces K^- p⟶ηΣ^0,ηΛ). Como esta última reacción también es sensible a las contribuciones de "NLO", sus correspondientes coeficientes serán más confiables. Esto hace que el estudio de la estabilidad adquiera un carácter más decisivo. Con esta motivación, se han extendido las contribuciones resonantes a los procesos K^- p⟶ηΛ, teniendo en cuenta para este caso particular solo la contribución de la resonancia Λ(1890). Esta última resonancia ha sido también incorporada, junto con las ya empleadas Σ(2030) y Σ(2250), a las amplitudes de dispersión K^- p⟶KΞ. Los resultados obtenidos confirman lo que ya se había observado con anterioridad: hay una notable mejora en la reproducción de los datos experimentales y los parámetros adquieren valores similares a los del correspondiente modelo sin resonancias. Esta estabilidad es especialmente remarcable para la mayoría de los coeficientes de "NLO". Habiendo demostrado los efectos de los procesos que filtran isospín sobre los coeficientes de "NLO", en el Capítulo 4 se muestra que la desintegración Λ_b⟶J/ψ ηΛ y, particularmente, la Λ_b⟶J/ψ KΞ proporcionan una información interesante relativa a la interacción mesón-barión en el sector S=-1 y I=0. La dinámica de esta reacción, en la cual los quarks ligeros que conforman la Λ_b actúan como espectadores, es tal que filtra el I=0 en los estados finales. Esto es así, ya que los quarks "u" y "d" en el barión Λ_b se acoplan necesariamente a isospín 0 y la desintegración débil favorece la transición b⟶cc ̅s; quedando, por lo tanto, un quark "s" al final del proceso débil, el cual tiene isospín 0 que junto al anterior par "ud" darán un isospín total I=0. Así pues, estas desintegraciones podrían ofrecer información complementaria a la que se obtiene de los datos de la reacción de dispersión K^- p⟶KΞ cuyas componentes de isospín I=0 y I=1 se combinan para dar los resultados finales. Basamos nuestro estudio en los modelos WT+NLO (Model 1) y WT+NLO+Born (η chan) (Model 2) que han sido desarrollados en esta tesis para describir la dispersión K^- p. Las distribuciones de masa invariante producidas por ambos modelos son diferentes para las desintegraciones de Λ_b a los estados KΞ y ηΛ, siendo a su vez bastante diferentes respecto al espacio fásico, indicando la sensibilidad de estos procesos a la dinámica interna de la interacción fuerte en los estados finales. La diferencia entre modelos es mucho más apreciable en el proceso de desintegración Λ_b⟶J/ψ KΞ. La razón se deriva del hecho que la desintegración en ηΛ puede proceder de manera directa ("tree level"), mientras que para la desintegración de Λ_b que da lugar a una J/ψ no permite una formación del par KΞ directamente, a no ser que este se produzca vía la redispersión de los componentes primarios K ̅N y ηΛ. Por tanto, la reacción Λ_b⟶J/ψ KΞ es directamente proporcional a la amplitud de dispersión mesón-barión, concretamente a las componentes de I=0 correspondientes a ηΛ⟶KΞ y K ̅N⟶KΞ cuya interferencia puede dar lugar a patrones muy marcados. Estos modelos también predicen diferencias notables para las desintegraciones Λ_b en las regiones de energía donde se producen los pares KΞ y ηΛ, poniendo de manifiesto que la componente de I=0 de la interacción mesón-barión, que es la única posible por provenir de la desintegración Λ_b, no está bien fijada por los ajustes a los datos experimentales de las reacciones K^- p⟶KΞ. Las dos estructuras halladas recientemente en la distribución de masa invariante J/ψ p de la desintegración Λ_b⟶J/ψ K^- p que han sido asociadas a dos estados de pentaquark, con su plausible explicación en términos de un estado molecular con un barión y un par cc ̅, nos llevaron a estudiar la desintegración de la Λ_b en los estados finales J/ψ ηΛ. La desintegración Λ_b⟶J/ψ ηΛ, que puede conectarse en canales acoplados a la desintegración Λ_b⟶J/ψ K^- p, podría tener lugar con la misma intensidad y sería posible observar, en su distribución de masa invariante J/ψ Λ, un posible compañero extraño de los dos estados de pentaquarks observados por la colaboración LHCb. Conviene tener presente que cuando las resonancias N^* de encanto escondido fueron teóricamente predichas como estados moleculares utilizando varios métodos basados en la unitarización, algunos compañeros extraños como los estados Λ_b fueron encontrados. Aprovechando esta información, hemos predicho qué tipo de señal dejarían estos estados en las distribuciones de masa invariante ηΛ y J/ψ Λ de la reacción Λ_b⟶J/ψ ηΛ. Hemos visto que tomando los valores de las constantes de acoplamiento del estado Λ^* de encanto escondido a los canales D ̅^(0*) Ξ_c^' y J/ψ Λ obtenidos por los métodos basados en la unitarización, uno observaría una señal clara y con un apreciable pico en la distribución de masa invariante J/ψ Λ de la desintegración Λ_b⟶J/ψ ηΛ. También se estudió la dependencia de nuestros resultados a cambios razonables en los parámetros que caracterizaban los modelos involucrados en nuestra descripción del proceso, así como la dependencia en las posibles propiedades de dicho pentaquark. En todos los tests que se realizaron, la señal resonante seguía siendo claramente visible en la distribución de masa invariante J/ψ Λ. Esto nos hace pensar que en el caso que se llevara a cabo tal experimento podría dar prueba de la existencia de este nuevo estado. Este trabajo ha sido un primer paso hacia la construcción de un modelo quiral más completo en el sector S=-1 que nos será útil para analizar los venideros datos más precisos de la producción KΞ. Además, los hallazgos y características observados en este estudio indican que la medida de observables analizados aquí proporcionaría una información valiosa, hasta ahora novedosa, que enriquecería nuestro conocimiento de la interacción mesón-barión y nos ayudaría a progresar en la comprensión de la dinámica de los hadrones.

Das Zusammenspiel von Hadronen und Modifikationen ihrer Eigenschaften auf der einen Seite und spontaner chiraler Symmetriebrechung und Restauration auf der anderen Seite wird untersucht. Es werden die QCD Summenregeln für D und B Mesonen in kalter Materie berechnet. Wir bestimmen die Massenaufspaltung von D - D-bar und B - B-bar Mesonen als Funktion der Kerndichte und untersuchen den Einfluss verschiedener Kondensate in der Näherung linearer Dichteabhängigkeit. Die Analyse beinhaltet ebenfalls D_s und D^*_0 Mesonen. Es werden QCD Summenregeln für chirale Partner mit offenem Charmfreiheitsgrad bei nichtverschwindenden Nettobaryonendichten und Temperaturen vorgestellt. Es wird die Differenz sowohl von pseudoskalaren und skalaren Mesonen, als auch von Axialvektor- und Vektormesonen betrachtet und die entsprechenden Weinberg-Summenregeln hergeleitet. Basierend auf QCD Summenregeln werden die Auswirkungen eines Szenarios auf das rho Meson untersucht, in dem alle chiral ungeraden Kondensate verschwinden wohingegen die chiral symmetrischen Kondensate ihren Vakuumwert behalten. Die komplementären Folgerungen einer Massenverschiebung und Verbreiterung der rho Mesonanregung werden diskutiert. Ein alternativer Zugang basierend auf gekoppelten Dyson-Schwinger- und Bethe-Salpeter-Gleichungen für Quarkbindungszustände wird untersucht. Zu diesem Zwecke wird die analytische Struktur des Quarkpropagators in der komplexen Ebene numerisch untersucht und die Möglichkeit getestet die Anwendbarkeit auf den Sektor der schwer-leicht Quark Systeme im skalaren und pseudoskalaren Kanal, wie dem D Meson, durch Variation des Impulsteilungsparameters zu erweitern. Die Lösungen der Dyson-Schwinger-Gleichung in der Wigner-Weyl-Phase der chiralen Symmetrie bei nichtverschwindenden Stromquarkmassen wird benutzt um den Fall einer expliziten Symmetriebrechung ohne spontane Symmetriebrechung zu untersuchen
The interplay of hadron properties and their modification in an ambient nuclear medium on the one hand and spontaneous chiral symmetry breaking and its restoration on the other hand is investigated. QCD sum rules for D and B mesons embedded in cold nuclear matter are evaluated. We quantify the mass splitting of D - D-bar and B - B-bar mesons as a function of the nuclear matter density and investigate the impact of various condensates in linear density approximation. The analysis also includes D_s and $D^*_0 mesons. QCD sum rules for chiral partners in the open-charm meson sector are presented at nonzero baryon net density or temperature. We focus on the differences between pseudo-scalar and scalar as well as vector and axial-vector D mesons and derive the corresponding Weinberg type sum rules. Based on QCD sum rules we explore the consequences of a scenario for the rho meson, where the chiral symmetry breaking condensates are set to zero whereas the chirally symmetric condensates remain at their vacuum values. The complementarity of mass shift and broadening is discussed. An alternative approach which utilizes coupled Dyson-Schwinger and Bethe-Salpter equations for quark-antiquark bound states is investigated. For this purpose we analyze the analytic structure of the quark propagators in the complex plane numerically and test the possibility to widen the applicability of the method to the sector of heavy-light mesons in the scalar and pseudo-scalar channels, such as the D mesons, by varying the momentum partitioning parameter. The solutions of the Dyson-Schwinger equation in the Wigner-Weyl phase of chiral symmetry at nonzero bare quark masses are used to investigate a scenario with explicit but without dynamical chiral symmetry breaking

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xiii, 141 p.; also includes graphics (some col.). Includes bibliographical references (p. 139-141). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--Ohio State University, 2003.
Title from first page of PDF file. Document formatted into pages; contains xi, 101 p.: ill. (some col.). Includes abstract and vita. Advisor: Klaus Honschied, Dept. of Physics. Includes bibliographical references (p. 99-101).

The present thesis describes two experiments performed in the storage ring CELSIUS at The Svedberg Laboratory in Uppsala. In the first experiment the importance of three - nucleon clustering in the six - nucelon system was investigated. The total cross section for the production of the ground state and the 3.56 MeV second excited state of 6Li in the 3He(3He,6Li)π+ reaction has been measured at two beam energies, 261.1 and 262.5 MeV, corresponding to center - of - mass energies 1.2 and 1.9 MeV above the production threshold for the 3.56 MeV state. For the ground state the result was 347 ± 84 ± 42 and 92 ± 84 ± 11 nb respectively. The result for the 3.56 MeV state, 104 ± 23 ± 12 and 56 ± 35 ± 7 nb respectively, is compared to the result of a previous study where the 3.56 MeV state was populated in the d(4He,6Li)π0 reaction. In the second experiment a clean sample of 5×105 eta mesons was prepared by means of the d(p,3He)η reaction. Eta production was tagged by the precise determination of the kinetic energy of the associated 3He ions. In the subsequent decay of eta mesons, channels with lepton - anti - lepton pairs were studied in the WASA detector. In a separate study properties of the WASA deuterium pellet target were investigated and in particular the effects on the beam of the beam - target interactions. In both sets of experiments the fused nuclear system was detected by means of a zero - degree spectrometer with a semiconductor detector telescope. Choosing the detectors to match the rather different requirements, precise information regarding the identity and the momentum of the detected ions could be obtained in both cases.

L'etude des transitions inclusives des mesons beaux vers les mesons charmes a pour objectif de sonder les processus lies a l'interaction forte dans les desintegrations faibles des mesons beaux. Mon travail propose une nouvelle methode de mesure du rapport d'embranchement de b en d#*#+. En meme temps, la largeur relative partielle de desintegration du boson z en une paire de quarks charmes est obtenue. La reconstruction du meson d#* en un kaon et trois pions est basee uniquement sur des criteres cinematiques bien maitrises dans la simulation. Ainsi l'efficacite de selection est estimee fidelement avec la simulation. La quantite de signal est calculee par un ajustement de la distribution de la masse reconstruite. Pour separer les deux sources de production du meson d#*, charme et beaute, le temps de vol, dont la distribution est connue, est prefere a l'impulsion dont la distribution est tres sensible a la modelisation de la fragmentation. Les formes en temps des signaux et du fond sont parametrisees respectivement sur les donnees simulees et reelles. Puis, ces parametres fixes ainsi que la proportion signal/bruit, la proportion charme/beaute est ajustee par un maximum de vraissemblance. Deux mesures sont ainsi obtenues, le taux de mesons d#* produits dans les evenements charmes et dans les evenements beaux. L'erreur statistique domine l'incertitude sur les resultats alors que la fragmentation intervient tres peu, l'erreur systematique principale etant l'incertitude sur la forme du temps de vol du fond. A partir des mesures connues du rapport d'embranchement du meson d#*, nous obtenons finalement le rapport d'embranchement inclusif du mesons b en mesons d#*#+ et la largeur relative partielle du boson z en quarks charmes.

Radiative Decays of the phi-meson to the scalar mesons f0(980) and a0(980) are investigated within the framework of charged kaon loop model for both point-like scalar mesons and for scalar mesons with extended structure. Then, the radiative phi-meson decay into neutral K-meson is studied via a two step mechanism in which the scalar mesons couple the final state to the phi-meson through the charged kaon loop. The branching ratio of this decay is calculated and it is shown that this reaction will not provide a significant background to the measurements of phi-meson into neutral K-meson states decay for testing CP violation.

Es werden Zerfallsbreiten des Omega Mesons im Vakuum und in kalter Kernmaterie im Rahmen eines aus Pionen und Rho Mesonen bestehenden hadronischen Modells untersucht. Ausgangspunkt ist eine störungstheoretische Entwicklung in Selbstenergiediagrammen. Im ersten Abschnitt der Arbeit wird die Lagrangedichte des Modells zusammengestellt. Zur Konstruktion der Wechselwirkung von Rho Meson und Pionen bzw. Photon wird das Eichkonzept benutzt. Dabei erhält das Rho Meson durch seine Pionwolke Beiträge zur Selbstenergie. Die starken Zerfälle des Omega Mesons im Vakuum ergeben sich aus der anomalen Brechung der axialen U(1)--Symmetrie. Im zweiten Teil dieser Arbeit werden Selbstenergiediagramme bis zur Zwei--Loop--Struktur ausgewertet. Bei gleichzeitiger Erklärung der Partialbreite im Omega --> Pi + Gamma Kanal führen die berechneten Beiträge zu 57% der experimentellen Partialbreite im 3 Pi--Kanal des Omega Mesons. Die weiteren berechneten semileptonischen Dalitz--Zerfallsbreiten des Omega Mesons können mit den experimentellen Daten in Übereinstimmung gebracht werden. Die Berechnung des mikroskopischen Formfaktors am Omega,Rho,Pi Vertex erlaubt Vergleiche mit experimentellen Daten und läßt auf weitere Beiträge zur Omega Selbstenergie von höheren Diagrammen schließen. Im dritten Teil der Arbeit wird das hadronische Modell des Omega Mesons auf kalte Kernmaterie angewendet. Ausgehend von den jeweiligen Medium--Modifikationen des Rho Mesons und Pions wird das Ein--Loop--Diagramm zur Omega Selbstenergie berechnet. Für ein bei einfacher Kerndichte ruhendes Omega Meson erhält man eine Breite von 60 MeV. Die Abhängigkeit der Breite vom Dreierimpuls des Omega Mesons ist mit einigen MeV gering. Außerdem ergibt sich eine relativ schnelle Sättigung der Breite mit Anwachsen der Kerndichte.

We study the masses of the low-lying charm and bottom mesons within the framework of heavy-hadron chiral perturbation theory. We work to third order in the chiral expansion, where meson loops contribute. In contrast to previous approaches, we use physical meson masses in evaluating these loops. This ensures that their imaginary parts are consistent with the observed widths of the D-mesons. The lowest odd- and even-parity, strange and non-strange mesons provide enough constraints to determine only certain linear combinations of the low-energy constants (LECs) in the effective Lagrangian. We comment on how lattice QCD could provide further information to disentangle these constants. Then we use the results from the charm sector to predict the spectrum of odd- and even-parity of the bottom mesons. The predicted masses from our theory are in good agreement with experimentally measured masses for the case of the odd-parity sector. For the even-parity sector, the $B$-meson states have not yet been observed; thus, our results provide useful information for experimentalists investigating such states. The near degeneracy of nonstrange and strange scalar $B$ mesons is confirmed in our predictions using $\mathrm{HHChPT}$. Finally,we show why previous approaches of using $\mathrm{HHChPT}$ in studying the mass degeneracy in the scalar states of charm and bottom meson sectors gave unsatisfactory results. Interactions between these heavy mesons are treated using effective theories similar to those used to study nuclear forces. We first look at a strongly-interacting channel which produces a bound or virtual state and a dimer state which couples weakly to a weakly-interacting channel to produce a narrow resonance. We also look at the short-range interactions in two channels. We consider two cases: two channels where one has a strong $s$-wave interaction which produces bound or virtual states, and a dimer state which couples weakly to weakly-coupled channels which in turn can produce narrow resonances. For each of these systems, we use well-defined power-counting schemes. The results can be used to investigate resonances in the charmonium and bottomonium systems. We demonstrate how the method can be applied to the $X(3872)$. The widths of the $X(3872)$ for decay processes to $\bar{D}^0 D^{*0}$ and $\bar{D}^0D^0\pi$ are calculated. We use these results to obtain the line shapes of the $X(3872)$ under different assumptions about the nature of this state.

Thesis (Ph. D.)--University of Oregon, 2008.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 117-118). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

Thesis (Ph. D.)--University of California, Riverside, 2009.
Includes abstract. Includes bibliographical references (leaves 104-105). Issued in print and online. Available via ProQuest Digital Dissertations.

La presente tesis se ha elaborado con la finalidad de elaborar alimentos homogenizados (papillas) salados y dulces para bebés entre los 6 y 12 meses de edad; ya que dicho periodo corresponde entre el inicio de la alimentación complementaria y el inicio en que el bebé empieza a ingerir una dieta similar a la del adulto. Con la finalidad de satisfacer la necesidad alimenticia de los bebés, se lanzará al mercado nuestro producto, que contendrá dos líneas de alimentos (salada y dulce), ambas altamente nutritivas, al contener cereales ricos en proteínas. Nuestros productos, serán ofrecidos para alimentar a bebés entre 6 y 12 meses de edad pertenecientes al NSE B y C, lo que significa un mercado potencial de 31,608 bebés, que deberían consumir, según la OMS 300 gramos diarios de alimentos complementario, lo que representa 3413 toneladas de alimentos complementarios al año. Inicialmente, tenemos como objetivo satisfacer el 3% del mercado potencial, lo que significaría alrededor de 102 toneladas anuales de alimento homogenizado.
Tesis

CP violation is a well established phenomenon for B and K mesons, but for D0 mesons, bound states made up of a quark-antiquark pair containing a charm quark, a conclusive answer to the question whether there is CP vio- lation or not, has yet to be determined. I show here the phenomenology of time-dependent CP asymmetries in charm decays, and discuss the implica- tions of experimental tests aimed at the measurement of CP violation in the interference between mixing and decays of charm mesons, in particular when studying the decay channels D0 ! h+h (h = K; ). The decay channels considered can also be used to constrain quantities that are poorly measured or still to be investigated, such as MIX and c;eff , provided that the e ects of penguin pollution are ignored. I considered correlated production of D0 mesons at the SuperB experiment and its planned asymmetric run at the charm threshold and performed a study of simulated events, nding that a boost factor = 0:28 would not be su cient to produce competitive re- sults; the desirable resolution on the decay vertex separation between two D mesons in an event can be obtained with = 0:9. Vertex detectors play the major role in this analysis and new vertex detectors with high granular- ity might help improving these studies. The reference pixels (25 25 m pixel sensors implementing a 4T architecture with a deep n-well implant) of the Cherwell sensor, studied within the ARACHNID Collaboration, might be a candidate as a vertexing/tracking system, in particular for the layers of an SVT which are just around the beam pipe. I show the results of a study performed with data collected during a test beam at CERN, where the Cherwell sensor has been irradiated with pion beams, in terms of the charge deposited in the pixels by the charged particles passing through it, and show that this is mostly collected by the eight pixels ring surrounding the pixel hit by the particle beam. This work culminates in the de nition of the clustering algorithm used by ARACHNID.

This thesis is dedicated to the study of radiative decays of B mesons at LHCb. At quark level, such decays are a b-sy transition and take place via a penguin loop and are sensitive to virtual contribution of New Physics, which can be indicated by an increase in the decay rates. These decays also offer the possibility to test the V-A structure of the Standard Model coupling in the processes mediated by loop penguin diagrams. In the decay Bs-ǿy, New Physics contribution can be probed by measuring the polarization of the photon in this decay. Systematic effects in the proper time reconstruction of the Bs in Bs-ǿy can bias the photon polarization measurement in this decay, which will reduce the sensitivity on the relevant New Physics parameter. The author studied those effects and developed ideas to calibrate them using Bd-K *y and Bs-J/ψǿ decays as control channels. These studies are mostly Monte Carlo based, due to a relatively small data set from the 2010 running. However, some studies and cross checks have indeed been performed with data. The author developed the trigger and stripping (another level of skimming the data, after the trigger) selections for Bs-ǿy and Bd-K*y decays, and made a major contribution to the selection of the first significant sample of Bd-K *y from the 2010 data set of LHCb.

This thesis introduces a representation of graphical data, progressive meshes, and its fields of usage. The main part of this work is mathematical representation of progressive meshes and the simplification algorithm, which leads to this representation. Examples of changes in progressive mesh representation are also part of this thesis, along with few examples. The result is an application that implements the calculation of the Progressive Meshes model representation

The scalar mesons have caused much debate amongst hadronic physicists for many years. Even today the number of scalars is hotly contested, and there is almost no agreement on the composition of any of the experimentally observed states, except perhaps for the K*(_0) (1430). This thesis attempts to shed light on both of these problems via the application of analyticity to two different quantities. Recently a number of authors have proposed the existence of a light, strange, scalar meson known as the k. We perform a direct search of the best available πK scattering data to determine whether or not this resonance exists. This is done by constructing contour integrals from these data and determining the number of poles present inside the contour. We do not need to model either the internal dynamics of the state nor the form of the background scattering. The number of poles found tells us the number of resonances present and their positions allow us to estimate the resonance parameters. We find that there is only one resonance in scalar πK scattering below 1800 MeV and this is identified with the established K*(_0)(1430). We find no evidence for the k. Secondly, applying Cauchy's Theorem to the vacuum polarisation function leads to a relation between experimental and theoretical integrals known as a Finite Energy Sum Rule (FESR). FESRs are used to explore the scalar, isoscalar non-strange current and allow us to determine which of the experimentally observed scalar, isoscalar mesons is most likely to be the uũ + dd state. We find that the lightest scalar, isoscalar uũ dd state is not the fo(980) as suggested by some authors, but is rather the light, broad object known as the fo(400 - 1200). We are also able to estimate the average light quark mass and find m(_q)(l GeV(^2)) = 4.7 ± 0.9 MeV which is consistent with the recent estimates of this quantity from unquenched lattice QCD.

xxvi, 199 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
The abundance of B mesons at B factories opens the door to the search in rare decays for physics outside of the Standard Model. Flavor-changing neutral current transitions proceed only via higher order in the Standard Model, resulting in a b [arrow right] s³y branching fraction of about 3 x 10 -4 , but hypothesized particles could alter the rate significantly. Decays of B mesons that proceed via this electroweak penguin diagram are an interesting example of flavor-changing neutral currents, due to the large number of accessible final states with observables that are sensitive to new processes. This dissertation describes the analyses of such decays B - [arrow right] p ³, B - [arrow right] £ 0 p ³, B - [arrow right] p and B - [arrow right] p using about 350 million B meson pairs recorded by the BABAR detector in the years 2001 through 2006. In addition to the decay rate, the distribution of the invariant mass of the baryon pair is presented, using a method for statistical unfolding. The analysis is the first of these decays at the BABAR experiment and lays the groundwork for future analyses of the branching fractions and angular correlations of b [arrow right] s decays containing A hyperons and other baryons at BABAR or higher luminosity B factories.
Adviser: James E. Brau