Performance of body fat and body mass index cutoffs in elevated blood pressure screening among male children and adolescents

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Age constraints and fine tuning in variable-mass particle models

VAMP (variable-mass particle) scenarios, in which the mass of the cold dark matter particles is a function of the scalar field responsible for the present acceleration of the Universe, have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and dark matter scale in the same way. We find that only a narrow region in parameter space leads to models with viable values for the Hubble constant and dark energy density today. In the allowed region, the dark energy density starts to dominate around the present epoch and consequently such models cannot solve the coincidence problem. We show that the age of the Universe in this scenario is considerably higher than the age for noncoupled dark energy models, and conclude that more precise independent measurements of the age of the Universe would be useful in distinguishing between coupled and noncoupled dark energy models.

A dynamical gluon mass solution in Mandelstam's approximation

We discuss the pure gauge Schwinger-Dyson equation for the gluon propagator in the Landau gauge within an approximation proposed by Mandelstam many years ago. We show that a dynamical gluon mass arises as a solution. This solution is obtained numerically in the full range of momenta that we have considered without the introduction of any ansatz or asymptotic expression in the infrared region. The vertex function that we use follows a prescription formulated by Cornwall to determine the existence of a dynamical gluon mass in the light cone gauge. The renormalization procedure differs from the one proposed by Mandelstam and allows for the possibility of a dynamical gluon mass. Some of the properties of this solution, such as its dependence on A(QCD) and its perturbative scaling behavior are also discussed.

Vacuum energy as a c-function for theories with dynamically generated masses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of the t(t)over-bar production cross section and top quark mass extraction using dilepton events in p(p)over-bar collisions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for high-mass resonances decaying into tau-lepton pairs in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of the dijet invariant mass cross section in p(p)over-bar collisions at root s=1.96 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

QCD effective charge and the structure function F-2 at small-x

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The small x behavior of the gluon strucutre function from total cross-sections

Within a QCD-based eikonal model with a dynamical infrared gluon mass scale we discuss how the small x behavior of the gluon distribution function at moderate Q(2) is directly related to the rise of total hadronic cross-sections. In this model the rise of total cross-sections is driven by gluon-gluon semihard scattering processes, where the behavior of the small x gluon distribtuion function exhibits the power law xg(x, Q(2)) = h(Q(2))x(-epsilon). Assuming that the Q(2) scale is proportional to the dynamical gluon mass one, we show that the values of h(Q(2)) obtained in this model are compatible with an earlier result based on a specific nonperturbative Pomeron model. We discuss the implications of this picture for the behavior of input valence-like gluon distributions at low resolution scales.

Chiral symmetry breaking in QCD-like gauge theories with a confining propagator and dynamical gauge boson mass generation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Combination of t(t)over-bar cross section measurements and constraints on the mass of the top quark and its decays into charged Higgs bosons

We combine measurements of the top quark pair production cross section in p (p) over bar collisions in the l + jets, ll, and tau l final states ( where l is an electron or muon) at a center of mass energy of root s = 1.96 TeV in 1 fb(-1) of data collected with the D0 detector. For a top quark mass of 170 GeV/c(2), we obtain sigma(t (t) over bar) = 8.18(-0.87)(+0.98) pb in agreement with the theoretical prediction. Based on predictions from higher order quantum chromodynamics, we extract a mass for the top quark from the combined t (t) over bar cross section, consistent with the world average of the top quark mass. In addition, the ratios of t (t) over bar cross sections in different final states are used to set upper limits on the branching fractions B(t -> H(+)b -> tau(+) vb) and B(t -> H(+)b -> c (s) over barb) as a function of the charged Higgs boson mass.

Pure spinor partition function and the massive superstring spectrum

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Inner satellites of Neptune: I the disturbing function

In this work, we focus our attention to the expansion of the disturbing function (R) which governs the dynamics of a satellite (natural or artificial) in the Neptune-Triton system. What makes this problem quite unusual, is the fact that a small inner satellite can be strongly disturbed by Triton which is moving in a highly inclined and retrograde orbit. These features are unique in our solar system. Although a lot of retrograde satellites are currently known, all of them have negligible mass and the), do not offer almost any perturbation on the others satellites. However, in the case of the inner satellites of Neptune, Triton is an interesting exception. In a highly inclined orbit, the perturbation it exerts on the neighbouring satellites of Neptune cannot be ignored even for the present scenario. However, in the future, this perturbation will be much more important because due to the tides, the orbit of Triton is contracting, whereas the semi major axes of the remaining inner satellites of Neptune will remain almost unaffected by the tides. In this work we first obtain the disturbing function in the retrograde case. After that, we generalize R for arbitrary inclination. Several numerical tests are presented and a possible future case of resonant configuration is briefly discussed as well. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

Modifications in the correlation function in poly(vinyl alcohol)/silica hybrid wet gels

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Persistence Length, Mass Fractal, and Branching in the Aggregating of Vinyltriethoxysilane-Derived Organic/Silica Hybrids

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)