43 research outputs found
On the energy dependence of the D^+/D^- production asymmetry
In this paper we discuss the origin of the asymmetry present in D meson
production and its energy dependence. In particular, we have applied the meson
cloud model to calculate the asymmetries in D^-/D^+ meson production in high
energy p-p collisions and find a good agreement with recent LHCb data. Although
small, this non-vanishing asymmetry may shed light on the role played by the
charm meson cloud of the proton.Comment: 8 pages, 8 figures. arXiv admin note: text overlap with
arXiv:hep-ph/000927
Tetraquark Production in Double Parton Scattering
We develop a model to study tetraquark production in hadronic collisions. We
focus on double parton scattering and formulate a version of the color
evaporation model for the production of the and of the
tetraquark, a state composed by the quarks. We find that
the production cross section grows rapidly with the collision energy
and make predictions for the forthcoming higher energy data of the LHC.Comment: 13 pages, 3 figures. Corrections in the text and reference
Avaliação : princÃpio de uma aprendizagem de qualidade
Orientadora : Professora Ma. Simony Rafaeli QuirinoMonografia (especialização) - Universidade Federal do Paraná, Setor de ..., Curso de Especialização em Coordenação PedagógicaInclui referênciasResumo : Este artigo procura verificar o que pensam os alunos sobre a avaliação escolar. Para isso, foram aplicados questionários a dezoito alunos de uma turma do 9º ano do ensino fundamental de uma escola localizada no municÃpio de Siqueira Campos/Paraná. Verificou-se a partir das respostas dos alunos que a avaliação ainda é vista como excludente e classificatória, mas também fundamental para demonstrar o nÃvel de aprendizagem e o que de fato aprendemos, proporcionando para os alunos a interpretação de seus avanços escolares
Nuclear effects on the longitudinal structure function at small x
We discuss the longitudinal structure function in nuclear DIS at small .
We work within the framework of universal parton densities obtained in DGLAP
analyses at NLO. We show that the nuclear effects on the longitudinal structure
function closely follow those on the gluon distribution. The error analyses
available from newest sets of nuclear PDFs also allow to propagate the
uncertainties from present data. In this way, we evaluate the minimal
sensitivity required in future experiments for this observable to improve the
knowledge of the nuclear glue. We further discuss the uncertainties on the
extraction of off nuclear targets, introduced by the usual assumption
that the ratio is independent of the nuclear size. We focus on the
kinematical regions relevant for future lepton-ion colliders.Comment: LaTeX, 12 pages, 4 eps figures; v2: reference added; v3: comments and
references added, results and conclusions unchanged, final versio
Constraining the nuclear gluon distribution in processes at RHIC
A systematic determination of the gluon distribution is of fundamental
interest in understanding the parton structure of nuclei and the QCD dynamics.
Currently, the behavior of this distribution at small (high energy) is
completely undefined. In this paper we analyze the possibility of constraining
the nuclear effects present in using the inclusive observables which
would be measured in the future electron-nucleus collider at RHIC. We
demonstrate that the study of nuclear longitudinal and charm structure
functions allows to estimate the magnitude of shadowing and antishadowing
effects in the nuclear gluon distribution.Comment: 6 pages, 3 eps figure
A importância da aplicação sequencial no controle de Elephantopus mollis
Elephantopus mollis, popularly known as elephant paw or sussuaiá, is a species that has recently emerged as a weed affecting grain crops. This study aimed to evaluate the differential sensitivity of biotypes of E. mollis obtained from agricultural and nonagricultural areas and to determine the best combinations of herbicides applied at different stages of development for controlling this species. Three ex- periments were conducted. In the differential sensitivity experiment, 10 herbicides were used in 2 biotypes in 2 stages of development. The dose–response experiment was conducted using 8 doses of 7 herbicides. The field experiment was conducted in an area with weed issues to validate the results of previous experiments. The biotype from the agricultural area showed lower sensitivity to herbicides than the biotype from the nonagricultural area. The contact herbicides initially presented better control; however, the weed shortly showed re-growth due to the presence of buds in the plant crown. Isolated application of 2.4-D amine at doses between 1005 and 1675 g a.e. ha−1 demonstrated 25% control. When 2,4-D amine was followed by paraquat application (400 g a.i. ha−1), the control observed was between 51% and 68%. The best treatment for the control of completely developed weeds is 2,4-D amine + glyphosate mixture (1340 + 1080 g a.e. ha−1), followed by sequential paraquat application.Popularmente conhecida como pata de elefante ou sussuaiá, Elephantopus mollis, é uma espécie que recentemente surgiu como uma planta daninha em lavouras de cultivos de grãos. Objetivou-se com este estudo avaliar a sensibilidade diferencial de biótipos de E. mollis oriundos de áreas agrÃcolas e não agrÃcolas e determinar as melhores combinações de herbicidas aplicados em diferentes estádios de desenvolvimento para o controle desta espécie. Foram realizados três experimentos. No experimento de sensibilidade diferencial foram utilizados dez herbicidas em dois biótipos em duas fases de desenvolvimento. O experimento de dose resposta foi conduzido com oito doses de sete herbicidas. O experimento a campo foi realizado em uma área que apresenta problemas com a planta daninha para validar os resultados dos experimentos anteriores. O biótipo oriundo de área agrÃcola apresentou menor sensibilidade aos herbicidas quando comparado ao biótipo oriundo de área não agrÃcola. Os herbicidas de contato inicialmente apresentam controle superior, mas logo a planta apresenta rebrote em função de gemas presentes no colo da planta. A aplicação isolada de 2,4-D com doses entre 1005 e 1675 g e.a ha-1 possui controle de 25%. Quando o 2,4-D é seguido da aplicação de paraquat (400 g i.a ha-1) o controle passa a ser entre 51 e 68%. O melhor tratamento para o con- trole de plantas desenvolvidas é a mistura de 2,4-D + glyphosate (1340 + 1080 g e.a ha-1) com aplicação sequencial de paraquat
Exclusive processes in electron - ion collisions
The exclusive processes in electron-ion () interactions are an important
tool to investigate the QCD dynamics at high energies as they are in general
driven by the gluon content of the target, which is strongly subject to parton
saturation effects. In this paper we compute the cross sections for the
exclusive vector meson production as well as the deeply virtual Compton
scattering (DVCS) relying on the color dipole approach and considering the
numerical solution of the Balitsky-Kovchegov equation including running
coupling corrections (rcBK). The production cross sections obtained with the
rcBK solution and bCGC parametrization are very similar, the former being
slightly larger.Comment: 6 pages, 4 figure