Analysis on the diffractive production of W's and dijets at the DESY HERA and Fermilab Tevatron colliders

Hadronic processes in which hard diffractive production takes place have been observed and analyzed in collider experiments for several years. The experimental rates of diffractive W's and dijets measured at the Tevatron and the cross sections of diffractively produced dijets recently obtained at the HERA experiment are the object of this analysis. We use the Pomeron structure function obtained from the HERA data by two different approaches to calculate the rates and cross sections for these processes. The comparison of theoretical predictions with the measured values reveals some discrepancies that make evident conceptual difficulties with such approaches. A new version of the Ingelman-Schlein model is proposed as an attempt to overcome such difficulties and make theory and data compatible.Comment: 31 pages, to be published in Phys. Rev. D. This version includes 6 corrected figure

On the choice of parameters in solar structure inversion

The observed solar p-mode frequencies provide a powerful diagnostic of the internal structure of the Sun and permit us to test in considerable detail the physics used in the theory of stellar structure. Amongst the most commonly used techniques for inverting such helioseismic data are two implementations of the optimally localized averages (OLA) method, namely the Subtractive Optimally Localized Averages (SOLA) and Multiplicative Optimally Localized Averages (MOLA). Both are controlled by a number of parameters, the proper choice of which is very important for a reliable inference of the solar internal structure. Here we make a detailed analysis of the influence of each parameter on the solution and indicate how to arrive at an optimal set of parameters for a given data set.Comment: 14 pages, 15 figures. Accepted for publication on MNRA

Teor de açúcar da água residuária do processamento do café.

A fermentação dos açúcares contidos na mucilagem da água residuária do café (ARC) possibilita obter álcool. Para se obter bom rendimento de álcool é necessário ajustar o teor de açúcar da ARC para 16° Brix. O trabalho teve como objetivo quantificar os teores de açúcar da ARC, após sucessivas reciclagens no processo de desmucilamento. Colocou-se água de torneira em amostras de café cereja descascado, das variedades Bourbon Vermelho e Bourbon Amarelo, e a mucilagem foi extraída, girando-se um bastão de vidro, por 3 minutos. Foram feitas até seis extrações, em seqüência, reciclando-se a ARC obtida. Os teores de açúcar da ARC aumentaram linearmente com o aumento do número de extrações realizadas. O teor de açúcar da ARC elevou-se de 3,1 para 9,3° Brix, após cinco extrações, e de 2,6 para 10,3° Brix, após seis extrações da mucilagem do cereja descascado, das variedades Bourbon Vermelho e Bourbon Amarelo, respectivamente

Experimental Determination of Thermal Entanglement in Spin Clusters using Magnetic Susceptibility Measurements

The present work reports an experimental observation of thermal entanglement in a clusterized spin chain formed in the compound Na$_2$Cu$_5$Si$_4$O$_{14}$. The presence of entanglement was investigated through two measured quantities, an Entanglement Witness and the Entanglement of Formation, both derived from the magnetic susceptibility. It was found that pairwise entanglement exists below $\sim 200$ K. Tripartite entanglement was also observed below $\sim 240$ K. A theoretical study of entanglement evolution as a function of applied field and temperature is also presented.Comment: Submited to Phys. Rev.