Longitudinal Target-Spin Asymmetries for Deeply Virtual Compton Scattering

A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6 GeV electron beam, a longitudinally polarized proton target, and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for ep. e\u27p\u27gamma. events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in Q(2), x(B), t, and phi, for 166 four-dimensional bins. In the framework of generalized parton distributions, at leading twist the t dependence of these asymmetries provides insight into the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. These results also bring important and necessary constraints for the existing parametrizations of chiral-even generalized parton distributions

Preliminary site report for the 2005 ICDP-USGS deep corehole in the Chesapeake Bay impact crater

First report for the ICDP-USGS 1.7-km-deep corehole drilled into the central part of the Chesapeake Bay impact crater during 2005

Design and Performance of SiPM-Based Readout of PbF\u3csub\u3e2\u3c/sub\u3e Crystals for High-Rate, Precision Timing Applications

We have developed a custom amplifier board coupled to a large-format 16-channel Hamamatsu silicon photomultiplier device for use as the light sensor for the electromagnetic calorimeters in the Muon g - 2 experiment at Fermilab. The calorimeter absorber is an array of lead-fluoride crystals, which produces short-duration Cherenkov light. The detector sits in the high magnetic field of the muon storage ring. The SiPMs selected, and their accompanying custom electronics, must preserve the short pulse shape, have high quantum efficiency, be non-magnetic, exhibit gain stability under varying rate conditions, and cover a fairly large fraction of the crystal exit surface area. We describe an optimized design that employs the new-generation of thru-silicon via devices. The performance is documented in a series of bench and beam tests

Fatores de caracterização da educação não formal: uma revisão da literatura

Resumo O presente artigo relata os resultados de uma investigação de caráter documental, na área da educação não formal. A educação não formal é uma área em expansão, à qual tem sido dada crescente atenção e importância. No entanto, é um setor do conhecimento, em geral, mal definido e ambíguo, no sentido em que os termos empregados são polissêmicos e não há consenso sobre seus usos e definições. Assim, com o objetivo de clarificar as definições das diferentes tipologias educativas, incluindo a educação não formal, perguntamos: que características têm estas tipificações educativas? Que critérios ou fatores são utilizados na literatura para defini-las? Com vista a responder a estas questões de pesquisa, realizamos uma revisão da literatura, analisando 28 documentos, entre literatura nacional e internacional, valendo-nos de técnicas de análise documental e análise de conteúdo. Apuramos que, na maioria da literatura nacional, a terminologia educação formal – não formal – informal é a mais utilizada. Confirmamos a dificuldade em se definir e estabelecer fronteiras entre as diferentes tipologias educativas e sublinhamos que as definições das mesmas envolvem um número elevado de fatores de diferentes naturezas. Investigamos 21 fatores usados nas caracterizações das diferentes tipologias educativas, divididos por quatro dimensões de análise: estrutura, processos, propósitos e conteúdos. Apuramos que, apesar da diversidade de fatores utilizados nas definições, há um núcleo adotado com mais frequência, associado principalmente a características estruturais, como localização, grau de planejamento ou duração da aprendizagem

A comparison of forward and backward pp pair knockout in 3He(e,e'pp)n

Measuring nucleon-nucleon Short Range Correlations (SRC) has been a goal of the nuclear physics community for many years. They are an important part of the nuclear wavefunction, accounting for almost all of the high-momentum strength. They are closely related to the EMC effect. While their overall probability has been measured, measuring their momentum distributions is more difficult. In order to determine the best configuration for studying SRC momentum distributions, we measured the $^3$He$(e,e'pp)n$ reaction, looking at events with high momentum protons ($p_p > 0.35$ GeV/c) and a low momentum neutron ($p_n< 0.2$ GeV/c). We examined two angular configurations: either both protons emitted forward or one proton emitted forward and one backward (with respect to the momentum transfer, $\vec q$). The measured relative momentum distribution of the events with one forward and one backward proton was much closer to the calculated initial-state $pp$ relative momentum distribution, indicating that this is the preferred configuration for measuring SRC.Comment: 8 pages, 9 figures, submitted to Phys Rev C. Version 2 incorporates minor corrections in response to referee comment