Effects of quark family nonuniversality in SU(3)_c X SU(4)_L X U(1)_x models

Flavour changing neutral currents arise in the $SU(3)_c\otimes SU(4)_L\otimes U(1)_X$ extension of the standard model because anomaly cancellation among the fermion families requires one generation of quarks to transform differently from the other two under the gauge group. In the weak basis the distinction between quark families is meaningless. However, in the mass eigenstates basis, the Cabibbo-Kobayashi-Maskawa mixing matrix motivates us to classify left-handed quarks in families. In this sense there are, in principle, three different assignments of quark weak eigenstates into mass eigenstates. In this work, by using measurements at the Z-pole, atomic parity violation data and experimental input from neutral meson mixing, we examine two different models without exotic electric charges based on the 3-4-1 symmetry, and address the effects of quark family nonuniversality on the bounds on the mixing angle between two of the neutral currents present in the models and on the mass scales $M_{Z_2}$ and $M_{Z_3}$ of the new neutral gauge bosons predicted by the theory. The heaviest family of quarks must transform differently in order to keep lower bounds on $M_{Z_2}$ and $M_{Z_3}$ as low as possible without violating experimental constraints.Comment: 27 pages, 10 tables, 2 figures. Equation (19) and typos corrected. Matches version to appear in Phys. Rev.

Metodologia para utilização de aeromodelos em monitoramento aéreo.

O projeto ARARA (Aeronaves de Reconhecimento assistidas por Rádio e Autônomas), está centrado no desenvolvimento e uso de UAV's, de escala reduzida, para monitoramento aéreo. Seu principal objetivo é a substituição de aeronaves convencionais utilizadas na obtenção de fotografias aéreas, para monitoramento de áreas agrícolas e áreas sujeitas a problemas ambientais, por UAV's de pequeno porte que realizam missões pré-estabelecidas pelos usuários.bitstream/CNPDIA/8116/1/CiT15_2002.pd

Second order perturbations of a Schwarzschild black hole: inclusion of odd parity perturbations

We consider perturbations of a Schwarzschild black hole that can be of both even and odd parity, keeping terms up to second order in perturbation theory, for the $\ell=2$ axisymmetric case. We develop explicit formulae for the evolution equations and radiated energies and waveforms using the Regge-Wheeler-Zerilli approach. This formulation is useful, for instance, for the treatment in the ``close limit approximation'' of the collision of counterrotating black holes.Comment: 12 pages RevTe

Safira: sistema de análise de fibras e raízes.

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Monitoramento Agrícola a Partir de Imagens Aéreas e WebMapping .

bitstream/CNPDIA/10446/1/BPD08_2004.pd