Combining exclusive semi-leptonic and hadronic B decays to measure |V_ub|

The Cabibbo-Kobayashi-Maskawa matrix element |V_ub| can be extracted from the rate for the semi-leptonic decay B -> pi + l + antineutrino_l, with little theoretical uncertainty, provided the hadronic form factor for the B -> pi transition can be measured from some other B decay. In here, we suggest using the decay B -> pi J\psi. This is a color suppressed decay, and it cannot be properly described within the usual factorization approximation; we use instead a simple and very general phenomenological model for the b d J\psi vertex. In order to relate the hadronic form factors in the B -> pi J\psi and B -> pi + l + antineutrino_l decays, we use form factor relations that hold for heavy-to-light transitions at large recoil.Comment: Latex, 7 pages, no figure

Origin and spectroscopic determination of trigonal anisotropy in a heteronuclear single-molecule magnet

W-band ({\nu} ca. 94 GHz) electron paramagnetic resonance (EPR) spectroscopy was used for a single-crystal study of a star-shaped Fe3Cr single-molecule magnet (SMM) with crystallographically imposed trigonal symmetry. The high resolution and sensitivity accessible with W-band EPR allowed us to determine accurately the axial zero-field splitting terms for the ground (S =6) and first two excited states (S =5 and S =4). Furthermore, spectra recorded by applying the magnetic field perpendicular to the trigonal axis showed a pi/6 angular modulation. This behavior is a signature of the presence of trigonal transverse magnetic anisotropy terms whose values had not been spectroscopically determined in any SMM prior to this work. Such in-plane anisotropy could only be justified by dropping the so-called 'giant spin approach' and by considering a complete multispin approach. From a detailed analysis of experimental data with the two models, it emerged that the observed trigonal anisotropy directly reflects the structural features of the cluster, i.e., the relative orientation of single-ion anisotropy tensors and the angular modulation of single-ion anisotropy components in the hard plane of the cluster. Finally, since high-order transverse anisotropy is pivotal in determining the spin dynamics in the quantum tunneling regime, we have compared the angular dependence of the tunnel splitting predicted by the two models upon application of a transverse field (Berry-phase interference).Comment: 13 pages, 9 figure

Coletânea de seminários técnicos 1986/88.

Estatística e informática, utilização do pacote SOC. Forrageiras e pastagens. Análises de laboratório visando a estimativa de qualidade das forrageiras. Avaliação da coleção de Panicum maximum no México e em Cuba. A biotecnologia de plantas no CNPGC: sofisticação dispensável ou inevitável. To Breed or not to Breed? um espaço para o melhoramento de plantas no CNPGC. Caracterização e avaliação do dano causado pelo adulto da cigarrinha-das-pastagens Zulia entreriana (Berg,1879) em Brachiaria decumbens Stapf cv. Basilisk. Citologia e modo de reprodução de oito gramíneas do gênero Brachiaria. Coleção de Brachiaria, processos na avaliação de germoplasma. O perfilhamento em gramíneas. Produção animal. Análise especial do gado de corte no Brasil. Avaliação da produção de carne em bovinos. Caracterização do Zebuíno de corte no Brasil; Estresse e produção animal. Modelo físico de produção - o caso do Campo experimental de Terenos-MS. Melhoramento e reprodução animal. Avaliação de reprodutores em Gado de corte, indução e sincronização do cio de fêmeas bovinas. Reações antígeno-anticorpo como instrumento de análise. Nutrição animal. Sinais indicativos de fluorose em bovinos suplementados com fosfato de rocha. Suplementação mineral em equinos. Uso potencial de fosfato natural como suplemento de fósforo para bovinos. Sanidade animal. E cruzando... que se ganha mais parasitas. Desenvolvimento de cepas vivas atenuadas de Babesia bovis e B. bigemina: teste reliminar. Epidemiologia da tristeza parasitária bovina e o diagnóstico sorológico. Epidemiologia e controle de helmintos gastrintestinais em bovinos de corte nos cerrados. Haematobia irritans, ecologia, importância e controle no Brasil. Investigações sobre a mortandade no rebanho bovino de Mato Grosso do Sul. Produção de cepas atenuadas de Babesia spp. E Anaplasma marginale para utilização na profilaxia da tristeza parasitária dos bovinos. Sorologia e epidemiologia de Anaplasma sp. e Babesia spp.bitstream/item/104712/1/Coletanea-de-seminarios.pd

Group Theory analysis of phonons in two-dimensional Transition Metal Dichalcogenides

Transition metal dichalcogenides (TMDCs) have emerged as a new two dimensional materials field since the monolayer and few-layer limits show different properties when compared to each other and to their respective bulk materials. For example, in some cases when the bulk material is exfoliated down to a monolayer, an indirect-to-direct band gap in the visible range is observed. The number of layers $N$ ($N$ even or odd) drives changes in space group symmetry that are reflected in the optical properties. The understanding of the space group symmetry as a function of the number of layers is therefore important for the correct interpretation of the experimental data. Here we present a thorough group theory study of the symmetry aspects relevant to optical and spectroscopic analysis, for the most common polytypes of TMDCs, i.e. $2Ha$, $2Hc$ and $1T$, as a function of the number of layers. Real space symmetries, the group of the wave vectors, the relevance of inversion symmetry, irreducible representations of the vibrational modes, optical selection rules and Raman tensors are discussed.Comment: 32 pages, 4 figure

Nonclassical correlation in NMR quadrupolar systems

The existence of quantum correlation (as revealed by quantum discord), other than entanglement and its role in quantum-information processing (QIP), is a current subject for discussion. In particular, it has been suggested that this nonclassical correlation may provide computational speedup for some quantum algorithms. In this regard, bulk nuclear magnetic resonance (NMR) has been successfully used as a test bench for many QIP implementations, although it has also been continuously criticized for not presenting entanglement in most of the systems used so far. In this paper, we report a theoretical and experimental study on the dynamics of quantum and classical correlations in an NMR quadrupolar system. We present a method for computing the correlations from experimental NMR deviation-density matrices and show that, given the action of the nuclear-spin environment, the relaxation produces a monotonic time decay in the correlations. Although the experimental realizations were performed in a specific quadrupolar system, the main results presented here can be applied to whichever system uses a deviation-density matrix formalism.Comment: Published versio

2DPHOT: A Multi-purpose Environment for the Two-dimensional Analysis of Wide-field Images

We describe 2DPHOT, a general purpose analysis environment for source detection and analysis in deep wide-field images. 2DPHOT is an automated tool to obtain both integrated and surface photometry of galaxies in an image, to perform reliable star-galaxy separation with accurate estimates of contamination at faint flux levels, and to estimate completeness of the image catalog. We describe the analysis strategy on which 2DPHOT is based, and provide a detailed description of the different algorithms implemented in the package. This new environment is intended as a dedicated tool to process the wealth of data from wide-field imaging surveys. To this end, the package is complemented by 2DGUI, an environment that allows multiple processing of data using a range of computing architectures.Comment: Accepted to PAS

NUMERICAL SIMULATION OF TEMPERATURE DISTRIBUTION ON METAL CASTING IN VERTICAL SOLIDIFICATION

The metals and alloys solidification can be defined as a transient heat transfer process. A liquid/solid transformation is followed by thermal energy liberation, with a movable boundary separating two phases with different thermophysical properties. The solidification is of great interest to mechanical and chemical engineers. It is a non-linear transient phenomenon, where heat transfer between the casting and the mold plays a important role. This paper aims to propose a study of heat flow from the casting to the mold using a numerical technique to compute the temperature history of all points inside the casting. The cooling process consists of water-cooled mold with heat being extracted only from the bottom, resulting in unidirectional vertical solidification. The ANSYS software was used to obtain the temperature distribution in the casting. Good agreement was obtained when the simulation results were compared with the experimental data