1,421 research outputs found
Threshold production of meta-stable bound states of Kaluza Klein excitations in Universal Extra Dimensions
We study the formation and detection at the next linear e^+e^- collider of
bound states of level-1 quark Kaluza-Klein excitations B_KK within a scenario
of universal extra-dimensions (UED). The interactions of such Kaluza-Klein
excitations are modeled by an alpha_s driven Coulomb potential. In order to
obtain the threshold cross-section, we employ the Green function method which
is known to properly describe the peaks below threshold and to yield a net
increase in the continuum region (above threshold) relative to the naive Born
cross-section. We study such effect at different values of the scale (R^-1) of
the extra-dimensions with an explicit calculation of the mass spectrum as given
by radiative corrections. The overall effect is roughly 2.7 at R^-1=300 GeV and
goes down to 2.2 at R^-1=1000 GeV and a relatively large number of events is
expected from N_events ~ 2.5*10^4 at R^-1=300 GeV down to N_events ~ 10^3 at
R^-1=1000 GeV at the anticipated annual integrated luminosity of L_0= 100
fb^-1. We finally discuss some potentially observable signatures such as the
multilepton channels 2j + 2l + missing energy, and 2j + 4l + missing energy for
which we estimate statistical significance >~ 2 for R^-1 up to 600 ~ 700 GeV.Comment: Accepted for publication in Phys. Rev. D. Enhanced version. 13 pages,
5 figures, 2 table
Bound states of UED level-1 KK quarks at the Linear Collider
We study the formation and detection at the next linear collider of
bound states of level-1 quark Kaluza-Klein excitations within a
scenario of universal extra-dimensions (UED).Comment: 11 pages, 2 figures. Contributed paper to the proceedings of LC09:
e+e- physics at the TeV scale and the Dark Matter connection. 21-24 September
2009, Perugia, Ital
HYDROCRACKING OF FISCHER-TROPSCH PRODUCTS
The hydrocracking behavior the product of a Fischer-Tropsch synthesis consisting of a C4–C30 mixture of paraffins and olefins on a platinum/amorphous silica–alumina catalyst has been analyzed and optimized. The influence of temperature on the selectiveness of the hydrocracking has been investigated. Time and temperature optimization was performed in order to obtain the best operating conditions for the enhancement of gasoline and diesel cuts
Non-Commutative Geometry and Measurements of Polarized Two Photon Coincidence Counts
Employing Maxwell's equations as the field theory of the photon, quantum
mechanical operators for spin, chirality, helicity, velocity, momentum, energy
and position are derived. The photon ``Zitterbewegung'' along helical paths is
explored. The resulting non-commutative geometry of photon position and the
quantum version of the Pythagorean theorem is discussed. The distance between
two photons in a polarized beam of given helicity is shown to have a discrete
spectrum. Such a spectrum should become manifest in measurements of two photon
coincidence counts. The proposed experiment is briefly described.Comment: Latex, 13 pages, 3 figure
Crescimento e produção de matéria seca de mudas de dendezeiro em função do tempo de pré-viveiro e da percentagem de ocupação da bandeja pelos tubetes.
Este trabalho teve como objetivo verificar a influência do tempo de permanência das mudas no pré-viveiro e da percentagem de ocupação da bandeja pelos tubetes no crescimento e na partição de matéria seca de mudas de dendezeiro
Optimization of osmotic dehydration of papaya followed by air-drying
FERNANDES, Fabiano A. N. et al. Optimization of Osmotic Dehydration of Papaya of followed by air-drying. Food Research Internation, v. 39, p. 492-498, 2006.ABSTRACT: Papayas are a fragile fruit; characteristic that limits large-scale exportation from the producing centers to countries in temperate
regions. Loss of fruit ranges from 10% to 40% and could be reduced if papayas were dried. The process of osmotic dehydration followed
by air-drying was studied and modeled for papaya preservation, so it could be optimized. The developed model has been validated with
experimental data and simulations have shown how the operating conditions affect the process. An optimization was done using the
model in order to search for the best operation condition that would reduce the total processing time
Controls on the erosion of the continental margin of southeast Brazil from cosmogenic 10Be in river sediments
The Atlantic Ocean coast region of southeast Brazil contains two coast-parallel mountain ranges (the Serra do Mar and Serra da Mantiqueira) generated by tectonic activity pulses tens of millions years after the main continental rift event occurred around 120 Ma. Although the short-term erosion rates for the region are established, the relative importance of the factors controlling erosion is poorly constrained. We combine new and published catchment-averaged erosion rates (n = 48) using in situ-produced 10Be concentrations in quartz from river sediments to establish the regional erosion pattern. The river catchments are (i) escarpment topography, (ii) high-altitude low-relief and (iii) mixed topography, which record how escarpment fronts are migrating inland. Ocean-facing coastal escarpment catchments of the Serra do Mar (ε = 18–53 m/Ma) can be eroded approximately twice as fast as continent-facing escarpment catchments in the Serra do Mar and Serra da Mantiqueira (ε = 7–24 m/Ma). The correlation between the normalized channel steepness index (ksn) and slope angle indicates that river incision and hillslope erosion processes combine to maintain the high relief. The Serra do Mar catchments define a mean slope angle threshold indicating that landslides are the dominant erosional process when slope angles in excess of ~30°. Tectonic activity is low and plays no significant role in driving erosion. A first-order relationship between erosion rate and precipitation-temperature across the region implies that climate plays a key role in soil production, river incision and in triggering erosional processes. Although the high topographic relief is a pre-condition for the occurrence of significant erosion, the climatic condition is the outlining factor of the regional variation in erosion rates
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