This Thesis presents measurements of the decays \Bm\to\Xi_c^0\bar{\Lambda}_c^-, \Bzb\to\Xi_c^+\bar{\Lambda}_c^- , \Bm\to\Lambda_c^+\bar{\Lambda}_c^-\Km, and \Bzb\to\Lambda_c^+\bar{\Lambda}_c^-\Kzb based on 228 million \upsbb decays collected with the \babar\ detector at the SLAC \pep2\ asymmetric-energy \B factory. The branching fraction of \Bm\to\Lambda_c^+\bar{\Lambda}_c^-\Km is measured to be $(1.22\pm0.16\pm 0.14\pm0.63)\times 10^{-3}$, and the branching fraction of $\Bz\to\Lambda_c^+\bar{\Lambda_c^-\Kzb$ is $(0.40\pm 0.33\pm 0.05 \pm 0.21)\times 10^{-3}$. The product $\BR(\Bm\to\Xi_c^0\bar{Lambda}_c^-)\times \BR(\Xi_c^0\to\Xi^-\pi^+)$ is measured to be $(2.04\pm0.59\pm0.26\pm0.53)\times 10^{-5}$, and $\BR(\Bzb\to\Xi_c^+\bar{\Lambda}_c^-)\times\BR(\Xi_c^+\to\Xi^-\pi^+\pi^+)$ is $(1.50\pm 1.07\pm 0.19 \pm 0.39)\times 10^{-5}$, where the uncertainties are statistical, systematic, and the uncertainty from the branching fraction $\BR(\Lambda_c^+\to\proton K^-\pi^+)$, respectively.

In the first part, the Compact Muon Solenoid (CMS) forward calorimeter design studies are presented. The forward calorimeter consists of quartz fibers embedded in a steel absorber. Radiation damage studies of the quartz fiber and the absorber as well as the results of the first pre-production prototype PPP-I are presented. In the second part the Ωc0 search studies at the SELEX (E781) experiment at FermiLab are presented. 107±22Ωc0 events were observed in three decay modes. The relative branching ratio Ωc0 → Ω−π−π+π+)/Β(Ωc0→ Ω−π+)$ is measured as 2.00 ± 0.45 (stat) ± 0.32 (sys).

In this thesis we have studied baryon resonances generated from the dynamical interaction of two hadrons. We are interested on this study as an alternative approach to explain the increasing number of observed charmed states which apparently do not fit into the traditional three quark picture of a baryon. In particular, we study baryon molecules with JP = ½ - which can be formed from the attractive interaction of a pseudoscalar meson (0-) and a ground state baryon (1/2+) in s-wave (L = 0). Therefore our aim is to contribute to the understanding of the observed charm baryon spectra by checking if the dynamical origin can explain those states which are candidates to be a baryon resonance with JP =1/2-. The important feature of our model is the description of the meson-baryon interaction in terms of the t-channel vector meson exchange which is fully solved without any approximation. The first part of the thesis is devoted to study these sort of baryon molecules in free space. In order to learn about the nature of a baryon it is important to study its different types of decays. For this reason, we will calculate the strong decays of dynamically generated resonances into meson-baryon components, as well as the electromagnetic transition of such hadron molecules into the lowest-lying ground states. In the second part of the thesis we have included medium and temperature effects on the formalism to study the properties of the charmed baryon resonant states in hot and dense matter. This will allow us as well to study the properties of charmed mesons (D, D, Ds and Ds) in the nuclear medium which will be simultaneously dressed in the self-consistent calculation for the first time. The behaviour of these mesons will influence the charmonium production whose suppression is connected with the possible formation of quark-gluon plasma at a dense matter and high temperature scenario. / En esta tesis se han estudiado las resonancias bariónicas generadas a partir de la interacción dinámica de dos hadrones. Estamos interesados en este estudio como un enfoque alternativo para explicar el creciente número de estados observados con quark encanto y que aparentemente no encajan en la imagen tradicional de tres quarks de un barión. En particular, se estudian las moléculas de bariones con JP = ½ - que pueden formarse a partir de la interacción atractiva de un mesón pseudoescalar (0-) y un barión del estado fundamental ( 1/2+) en onda s (L = 0). Por tanto, nuestro objetivo es comprobar si el origen dinámico puede explicar aquellos estados que son candidatos a ser una resonancia bariónica con JP =1/2-. La característica importante del modelo es la descripción de la interacción mesón-barión en términos del canal t de intercambio de mesones vectoriales, que está resuelto sin ningún tipo de aproximación.La primera parte de la tesis está dedicada a estudiar este tipo de moléculas en el espacio libre. Con el fin de aprender sobre la naturaleza de un barión es importante estudiar sus diferentes tipos de desintegración. Por esta razón, calculamos las desintegraciones fuertes de las resonancias en canales mesón-barión, así como la transición electromagnética a bariones de estado fundamental.En la segunda parte de la tesis se ha incluido en el formalismo los efectos del medio y de la temperatura para estudiar las propiedades de los estados de bariones encantados en materia caliente y densa. Esto nos permitirá también estudiar las propiedades de los mesones encantados (D, D, Ds y Ds) en el medio nuclear, que serán vestidos autoconsistentemente en el cálculo por primera vez. El comportamiento de estos mesones influirá en la producción de “charmonium”, cuya supresión está relacionada con la posible formación de plasma de quark-gluón en materia densa y caliente.