13,587 research outputs found
Transverse parton momenta in single inclusive hadron production in annihilation processes
We study the transverse momentum distributions of single inclusive hadron
production in annihilation processes. Although the only
available experimental data are scarce and quite old, we find that the
fundamental features of transverse momentum dependent (TMD) evolution,
historically addressed in Drell-Yan processes and, more recently, in
Semi-inclusive deep inelastic scattering processes, are visible in annihilations as well. Interesting effects related to its non-perturbative
regime can be observed. We test two different parameterizations for the
dependence of the cross section: the usual Gaussian distribution and
a power-law model. We find the latter to be more appropriate in describing this
particular set of experimental data, over a relatively large range of
values. We use this model to map some of the features of the data within the
framework of TMD evolution, and discuss the caveats of this and other possible
interpretations, related to the one-dimensional nature of the available
experimental data
Flexible Parametrization of Generalized Parton Distributions: The Chiral-Odd Sector
We present a physically motivated parameterization of the chiral-odd
generalized parton distributions. The parametrization is an extension of our
previous one in the chiral-even sector which was based on the reggeized diquark
model. While for chiral even generalized distributions a quantitative fit with
uncertainty estimation can be performed using deep inelastic scattering data,
nucleon electromagnetic, axial and pseudoscalar form factors measurements, and
all available deeply virtual Compton scattering data, the chiral-odd sector is
far less constrained. While awaiting the analysis of measurements on
pseudoscalar mesons exclusive electroproduction which are key for the
extraction of chiral odd GPDs, we worked out a connection between the
chiral-even and chiral-odd reduced helicity amplitudes using Parity
transformations. The connection works for a class of models including
two-components models. This relation allows us to estimate the size of the
various chiral odd contributions and it opens the way for future quantitative
fits.Comment: 35 pages, 18 figures, text changes, corrected typos, added fig.
Viscosity and tribology of copper oxide nanofluids
Nanofluids, a term proposed by Choi in 1995 [1], are composites consisting of solid nanoparticles with sizes varying generally from 1 to 100 nm dispersed in a liquid. Numerous nanoparticles used as oil additives have been investigated in recent years [2-7]. Results show that they deposit on the rubbing surface and improve the tribological properties of the base oil, displaying good friction and wear reduction characteristics even at concentrations below 2%wt. Although the viscosity of the nanofluids is a property of crucial importance for film forming, and hence friction and wear reduction, which are characteristic of lubricants, only Hwang et al. [8] have studied thermal characteristics, kinematic viscosity and tribological properties of nanofluids simultaneously. In this paper, we present measurements of dynamic viscosity of nanofluids formed by copper oxide nanoparticles dispersed in a polyalphaolefin, for temperatures and concentrations varying from 20 to 60ÂșC and 0.5 to 2% wt., respectively. Dependence of the nanofluid viscosity to the solid fraction and temperature was compared with existing models and its influence on lubrication was also analysed
A linear filter to reconstruct the ISW effect from CMB and LSS observations
The extraction of a signal from some observational data sets that contain
different contaminant emissions, often at a greater level than the signal
itself, is a common problem in Astrophysics and Cosmology. The signal can be
recovered, for instance, using a simple Wiener filter. However, in certain
cases, additional information may also be available, such as a second
observation which correlates to a certain level with the sought signal. In
order to improve the quality of the reconstruction, it would be useful to
include as well this additional information. Under these circumstances, we have
constructed a linear filter, the linear covariance-based filter, that extracts
the signal from the data but takes also into account the correlation with the
second observation. To illustrate the performance of the method, we present a
simple application to reconstruct the so-called Integrated Sachs-Wolfe effect
from simulated observations of the Cosmic Microwave Background and of
catalogues of galaxies.Comment: 8 pages, 6 figures, accepted for publication in the IEEE Journal of
Selected Topics in Signal Processin
Sidebranching induced by external noise in solutal dendritic growth
We have studied sidebranching induced by fluctuations in dendritic growth.
The amplitude of sidebranching induced by internal (equilibrium) concentration
fluctuations in the case of solidification with solutal diffusion is computed.
This amplitude turns out to be significantly smaller than values reported in
previous experiments.The effects of other possible sources of fluctuations (of
an external origin)are examined by introducing non-conserved noise in a
phase-field model. This reproduces the characteristics of sidebranching found
in experiments. Results also show that sidebranching induced by external noise
is qualitatively similar to that of internal noise, and it is only
distinguished by its amplitude.Comment: 13 pages, 5 figure
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