The improved nuclear parton distributions

In this paper we propose an improvement of the EKS nuclear parton distributions for the small x region of high energy processes, where the perturbative high parton density effects cannot be disregarded. We analyze the behavior of the ratios $xG_A/xG_N$ and $F_2^A/F_2^D$ and verify that at small x they are strongly modified when compared to the EKS predictions. The implications of our results for the heavy ion collisions in RHIC and LHC are discussed.Comment: 16 pages, 2 figure

Scaling violation and shadowing corrections at HERA

We study the value of shadowing corrections (SC) in HERA kinematic region in Glauber - Mueller approach. Since the Glauber - Mueller approach was proven in perturbative QCD in the double logarithmic approximation (DLA), we develop the DLA approach for deep inelastic structure function which takes into account the SC. Our estimates show small SC for $F_2$ in HERA kinematic region while they turn out to be sizable for the gluon structure function. We compare our estimates with those for gluon distribution in leading order (LO) and next to leading order (NLO) in the DGLAP evolution equations.Comment: 9pp,6 figures in eps file

Jpsi and dielectron photoproduction measurements with PHENIX

Jpsi and dielectron photoproduction measurements in ultra-peripheral Au+Au collisions at 200 GeV with the PHENIX experiment are presented. The triggered events correspond to those accompanied with forward neutron emission from the Au dissociation. Jpsi and high-mass dielectron cross sections and pT distributions are consistent with various theoretical calculations.Comment: 4 pages, figures updated - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Impact parameter dependent S-matrix for dipole-proton scattering from diffractive meson electroproduction

We extract the S-matrix element for dipole-proton scattering using the data on diffractive electroproduction of vector mesons at HERA. By considering the full t dependence of this process we are able to reliably unfold the profile of the S-matrix for impact parameter values b>0.3 fm. We show that the results depend only weakly on the choice of the form for the vector meson wave function. We relate this result to the discussion about possible saturation effects at HERA.Comment: 15 pages, 6 figure

Nuclear shadowing from exclusive quarkonium photoproduction at the BNL RHIC and CERN LHC

The photonuclear production of vector mesons in ultraperipheral heavy ion collisions is investigated within the collinear approach using different parameterizations for the nuclear gluon distribution. The integrated cross section and the rapidity distribution for the $AA \to V AA$ ($V = J/\Psi, \Upsilon$) process are computed for energies of RHIC and LHC. A comparison with the recent PHENIX data on coherent production of $J/\Psi$ mesons is also presented. We demonstrate that the study of the exclusive quarkonium photoproduction can be used to constrain the nuclear effects in the gluon distribution.Comment: 8 pages, 4 figures, 2 tables. Version to be published in Physical Review

A EDUCAÇÃO TUTORIAL NA PERSPECTIVA DA TEORIA HISTÓRICO CULTURAL DA ATIVIDADE

Neste trabalho apresento a proposta de utilizar a Teoria Histórico Cultural da Atividade como referencial teórico para compreender o processo de formação associado à Educação Tutorial como realizada no Programa de Educação Tutorial

O PROCESSO DE FORMAÇÃO DA FILOSOFIA DA AVALIAÇÃO DO PROGRAMA DE EDUCAÇÃO TUTORIAL

A filosofia da avaliação do Programa de Educação Tutorial é analisada a partir dos elementos que a constituíram quando da publicação do Manual de Orientações Básicas de 2002. A proposta de avaliação se constituiu a partir da combinação de dois fatores. Primeiro, os encaminhamentos sobre avaliação oriundos do GT de avaliação do VI ENAPET e, segundo, as características da avaliação institucional propostas pelo Programa de Avaliação Nacional Institucional das Universidades Brasileiras, o PAIUB. A confluência desses dois conjuntos de conceitos permitiu a construção de uma proposta de avaliação consistente com a filosofia do programa, com a construção contínua da identidade dos grupos e consistente com o binômio autonomia/avaliação. Concluo que a reafirmação da filosofia de avaliação do PET é fundamental para estabelecer o cenário sobre o qual deve ser construído o processo de avaliação nacional do programa

Scaling violation and shadowing corrections at HERA

We study the value of shadowing corrections (SC) in the HERA kinematic region in the Glauber{ Mueller approach. Since the Glauber{Mueller approach was proven in perturbative quantum chromodynamics (QCD) in the double-logarithmic approximation (DLA), we develop the DLA approach for the deep inelastic structure function which takes into account the SC. Our estimates show small SC for F2 in the HERA kinematic region while they turn out to be sizable for the gluon structure function. We compare our estimates with those for gluon distribution in leading order (LO) and next to leading order (NLO) in the DGLAP evolution equations