374 research outputs found
Investigating the effects of the QCD dynamics in the neutrino absorption by the Earth's interior at ultrahigh energies
The opacity of the Earth to incident ultra high energy neutrinos is directly
connected with the behaviour of the neutrino - nucleon () cross
sections in a kinematic range utterly unexplored. In this work we investigate
how the uncertainties in due the different QCD dynamic models
modify the neutrino absorption while they travel across the Earth. In
particular, we compare the predictions of two extreme scenarios for the high
energy behaviour of the cross section, which are consistent with the current
experimental data. The first scenario considered is based on the solution of
the linear DGLAP equations at small- and large-, while the second one
take into account the unitarity effects in the neutrino - nucleon cross section
by the imposition of the Froissart bound behaviour in the nucleon structure
functions at large energies. Our results indicate that probability of
absorption and the angular distribution of neutrino events are sensitive to the
the QCD dynamics at ultra high energies.Comment: 6 pages, 3 figures. Improved version to be published in Physical
Review
Heavy Quark Production in Ultra High Energy Cosmic Ray Interactions
In this paper we present a comprehensive study of the heavy quark production
in ultra high energy cosmic ray interactions in the atmosphere considering that
the primary cosmic ray can be either a photon, neutrino or a proton. The
analysis is performed using a unified framework -- the dipole formalism --- and
the saturation effects, associated to the physical process of parton
recombination, are taken into account. We demonstrate that the contribution of
heavy quarks for cosmic ray interactions is in general non-negligible and can
be dominant depending of the process considered. Moreover, our results indicate
that new dynamical mechanisms should be included in order to obtain reliable
predictions for the heavy quark production in collisions at ultra high
cosmic ray energies.Comment: 8 pages, 5 figures. Enlarged version to be published in Astroparticle
Physic
Estimating nonlinear QCD effects in ultrahigh energy neutrino events at IceCube
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGSThe number of ultrahigh energy events at IceCube is estimated, for the first time, taking into account nonlinear QCD effects in the neutrino-hadron cross section. We assume that the extragalactic neutrino flux is given by Phi(v)(E-v) = Phi E-0(v)-2 and estimate the neutrino-hadron cross section using the dipole approach and a phenomenological model for the dipole-hadron cross section based on nonlinear QCD dynamics. We demonstrate that the nonlinear prediction is able to describe the current IceCube data and that the magnitude of the nonlinear effects is larger than 20% for visible energies of order of 2 PeV and increases with the neutrino energy. Our main conclusion is that the nonlinear QCD effects are non-negligible and should be taken into account in the analysis of the number of ultrahigh energy events.90515CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGSCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGSSem informaçãoSem informaçãoSem informaçã
Topical ophthalmic antimicrobials: unfulfilled demands and possibility of new investments in Brazil and in the United States
In general, topical ophthalmic drug products, especially those used for treating infections, present low effectiveness because of various reasons, from unfavorable drug physicochemical properties to physiological protective mechanisms of the eye. The fact is such group of products holds room for improvement, which could mean the development of better drugs or dosage forms. To achieve this, the knowledge of market composition is essential. The present work studied and compared the antimicrobial ophthalmic markets of Brazil and of the United States (US). Official databank of Brazilian Health Regulatory Agency and of US Food and Drug Administration were assessed for registered antimicrobial topical ophthalmic drug products. Brazilian market has registered greater number of drug products (119) than the US (94), but the latter involves more variety of substances and dosage forms. In both countries, non-innovative products registered as solutions of antibacterials, especially fluoroquinolones and aminoglycosides lead the market. Despite the clinical demand, the US has only one group of antimycotics (polyenes) registered, while in Brazil, there is not any ophthalmic antimycotic product marketed. This study evidences there is not only space for development of newer drugs and formulations but also a demand for already existing technologies and products in both countries
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