A comprehensive treatment of electromagnetic interactions and the three-body spectator equations

We present a general derivation the three-body spectator (Gross) equations and the corresponding electromagnetic currents. As in previous paper on two-body systems, the wave equations and currents are derived from those for Bethe-Salpeter equation with the help of algebraic method using a concise matrix notation. The three-body interactions and currents introduced by the transition to the spectator approach are isolated and the matrix elements of the e.m. current are presented in detail for system of three indistinguishable particles, namely for elastic scattering and for two and three body break-up. The general expressions are reduced to the one-boson-exchange approximation to make contact with previous work. The method is general in that it does not rely on introduction of the electromagnetic interaction with the help of the minimal replacement. It would therefore work also for other external fields

An introduction to the Generalized Parton Distributions

The concepts of Generalized Parton Distributions (GPD) are reviewed in an introductory and phenomenological fashion. These distributions provide a rich and unifying picture of the nucleon structure. Their physical meaning is discussed. The GPD are in principle measurable through exclusive deeply virtual production of photons (DVCS) or of mesons (DVMP). Experiments are starting to test the validity of these concepts. First results are discussed and new experimental projects presented, with an emphasis on this program at Jefferson Lab.Comment: 5 pages, 3 figures Proc. Int. Conf. on Quark Nuclear Physics (QNP2002), to be published in Eur. Phys. Jour.

Analyse de la mise en œuvre de la pédagogie Montessori dans deux écoles du primaire en Haïti

En Haïti, le système éducatif est en pleine réforme. En privilégiant l’Approche par Compétences (APC), les nouvelles politiques amènent les responsables des écoles et les enseignants à utiliser des méthodes pédagogiques actives. Les efforts sont réalisés dans ce sens en particulier par des établissements privés. Toutefois, les méthodes pédagogiques qui permettent l’application de l’APC dans les écoles primaires en Haïti restent méconnues ou mal connues. Cette étude évalue la mise en oeuvre de la pédagogie Montessori telle qu’utilisée par les enseignants au niveau du primaire. À travers la littérature nous avons pu dégager cinq principes que sont la liberté, le respect du rythme, la motivation intrinsèque, la manipulation et l’apprentissage coopératif ainsi que les pratiques pédagogiques. Nous avons élaboré deux questionnaires pour des entretiens semi-structurés et des grilles d’observation qui nous ont permis d’évaluer la compréhension des principes, leur mise en œuvre. Les résultats ont permis d’avancer que la plupart des pratiques des enseignants sont conformes à ce qui a été retenu dans le cadre théorique. Les pratiques et les modifications apportées dépendent de la compréhension du principe par l’enseignant, de l’emploi du temps et du contexte environnemental. Mots clés : pédagogie Montessori, mise en œuvre, pratiques enseignantes, Haïti, école primaireThe education system in Haiti is currently undergoing major reforms. The new policies favor the implementation of the Competency Based Approach, encouraging school leaders and teachers to use more proactive teaching methods. Efforts are already being made by some schools, private ones for the most part. However, those methods still remain fairly or poorly known by the teaching staff. This study aims to assess the implementation of Montessori pedagogy currently used by teachers at the primary level. Through the literature we were able to identify five principles that are freedom, respect for rhythm, intrinsic motivation, manipulation and cooperative learning and teaching practices. We developed two questionnaires for semi-structured interviews and observation grids that allowed us to assess the understanding of the principles and their implementation. The results suggested that most of the teachers' practices are in compliance with the principle of Montessori approaches. Adjustments were made to consider the teacher's understanding of the principle, the school schedule and environmental context. Keywords: Montessori pedagogy, implementation, teaching practices, primary school, elementary school, Hait

Introducing a rainfall compound distribution model based on weather patterns sub-sampling

This paper presents a probabilistic model for daily rainfall, using sub-sampling based on meteorological circulation. We classified eight typical but contrasted synoptic situations (weather patterns) for France and surrounding areas, using a "bottom-up" approach, i.e. from the shape of the rain field to the synoptic situations described by geopotential fields. These weather patterns (WP) provide a discriminating variable that is consistent with French climatology, and allows seasonal rainfall records to be split into more homogeneous sub-samples, in term of meteorological genesis. <br><br> First results show how the combination of seasonal and WP sub-sampling strongly influences the identification of the asymptotic behaviour of rainfall probabilistic models. Furthermore, with this level of stratification, an asymptotic exponential behaviour of each sub-sample appears as a reasonable hypothesis. This first part is illustrated with two daily rainfall records from SE of France. <br><br> The distribution of the multi-exponential weather patterns (MEWP) is then defined as the composition, for a given season, of all WP sub-sample marginal distributions, weighted by the relative frequency of occurrence of each WP. This model is finally compared to Exponential and Generalized Pareto distributions, showing good features in terms of robustness and accuracy. These final statistical results are computed from a wide dataset of 478 rainfall chronicles spread on the southern half of France. All these data cover the 1953–2005 period

Sensitivity of tensor analyzing power in the process d+p→d+Xd+p\to d+X to the longitudinal isoscalar form factor of the Roper resonance electroexcitation

The tensor analyzing power of the process $d + p \to d + X$, for forward deuteron scattering in the momentum interval 3.7 to 9 GeV/c, is studied in the framework of $\omega$ exchange in an algebraic collective model for the electroexcitation of nucleon resonances. We point out a special sensitivity of the tensor analyzing power to the isoscalar longitudinal form factor of the Roper resonance excitation. The main argument is that the $S_{11}(1535)$, $D_{13}(1520)$ and $S_{11}(1650)$ resonances have only isovector longitudinal form factors. It is the longitudinal form factor of the Roper excitation, which plays an important role in the $t-$dependence of the tensor analyzing power. We discuss possible evidence of swelling of hadrons with increasing excitation energy.Comment: 12 pages, 10 figure

Analytical Form of the Deuteron Wave Function Calculated within the Dispersion Approach

We present a convenient analytical parametrization of the deuteron wave function calculated within dispersion approach as a discrete superposition of Yukawa-type functions, in both configuration and momentum spaces.Comment: 3 pages, 2 figure; several minor corrections adde

Sources of short-lived bromocarbons in the Iberian upwelling system

Seawater concentrations of the four brominated trace gases dibromomethane (CH2Br2), bromodichloromethane (CHBrCl2), dibromochloromethane (CHBr2Cl) and bromoform (CHBr3) were measured at different depths of the water column in the Iberian upwelling off Portugal during summer 2007. Bromocarbon concentrations showed elevated values in recently upwelled and aged upwelled waters (mean values of 30 pmol L−1 for CHBr3), while values in the open ocean were significantly lower (7.4 pmol L−1 for CHBr3). Correlations with biological variables and marker pigments indicated that phytoplankton could be identified as a weak bromocarbon source in the open ocean. In upwelled water masses along the coast, halocarbons were not correlated to Chl-a, indicating an external source, overlapping the possible internal production by phytoplankton. We showed that the tidal frequency had a significant influence on halocarbon concentrations in the upwelling and we linked those findings to a strong intertidal coastal source, as well as to a transport of those halocarbon enriched coastal waters by westward surface upwelling currents. Coastal sources and transport can be accounted for maximum values of up to 185.1 pmol L−1 CHBr3 in the upwelling. Comparison with other productive marine areas revealed that the Iberian upwelling had stronger halocarbon sources than the phytoplankton dominated sources in the Mauritanian upwelling. However, the concentrations off the Iberian Peninsula were still much lower than those of coastal macroalgal influenced waters or those of polar regions dominated by cold water adapted diatom

Generalized parton distributions in the deuteron

We introduce generalized quark and gluon distributions in the deuteron, which can be measured in exclusive processes like deeply virtual Compton scattering and meson electroproduction. We discuss the basic properties of these distributions, and point out how they probe the interplay of nucleon and parton degrees of freedom in the deuteron wave function

The HPS electromagnetic calorimeter

The Heavy Photon Search experiment (HPS) is searching for a new gauge boson, the so-called “heavy photon.” Through its kinetic mixing with the Standard Model photon, this particle could decay into an electron-positron pair. It would then be detectable as a narrow peak in the invariant mass spectrum of such pairs, or, depending on its lifetime, by a decay downstream of the production target. The HPS experiment is installed in Hall-B of Jefferson Lab. This article presents the design and performance of one of the two detectors of the experiment, the electromagnetic calorimeter, during the runs performed in 2015–2016. The calorimeter's main purpose is to provide a fast trigger and reduce the copious background from electromagnetic processes through matching with a tracking detector. The detector is a homogeneous calorimeter, made of 442 lead-tungstate (PbWO4) scintillating crystals, each read out by an avalanche photodiode coupled to a custom trans-impedance amplifier