47,504 research outputs found
Parton Distributions Functions of Pion, Kaon and Eta pseudoscalar mesons in the NJL model
Parton distributions of pseudoscalar pi,K and eta mesons obtained within the
NJL model using the Pauli-Villars regularization method are analyzed in terms
of LO and NLO evolution, and the valence sea quark and gluon parton
distributions for the pion are obtained at Q^2 = 4 GeV^2 and compared to
existing parametrizations at that scale. Surprisingly, the NLO order effects
turn out to be small compared to the LO ones. The valence distributions are in
good agreement with experimental analyses, but the gluon and sea distributions
come out to be softer in the high-x region and harder in the low-x region than
the experimental analyses suggest.Comment: (Latex, epsfig) 17 pages, 7 figure
Instability of Amorphous Ru-Si-O Thin Films under Thermal Oxidation
Ternary films about 200 nm thick of composition Ru20Si15O65 have been synthesized by reactive rf magnetron sputtering of a Ru1Si1 target in an argon-oxygen gas. As-deposited, the films are X-ray-amorphous. Their atomic density is 8.9 × 10^22/cm^3 (5.1 g/cm^3), and their electrical resistivity is in the range of 2 mOmega cm. After annealing in dry oxygen at 600°C for 30 min, micron-sized grains of RuO2 grow out of the film and volatile RuO4 escapes. The significance of these results is discussed
A Coverage Study of the CMSSM Based on ATLAS Sensitivity Using Fast Neural Networks Techniques
We assess the coverage properties of confidence and credible intervals on the
CMSSM parameter space inferred from a Bayesian posterior and the profile
likelihood based on an ATLAS sensitivity study. In order to make those
calculations feasible, we introduce a new method based on neural networks to
approximate the mapping between CMSSM parameters and weak-scale particle
masses. Our method reduces the computational effort needed to sample the CMSSM
parameter space by a factor of ~ 10^4 with respect to conventional techniques.
We find that both the Bayesian posterior and the profile likelihood intervals
can significantly over-cover and identify the origin of this effect to physical
boundaries in the parameter space. Finally, we point out that the effects
intrinsic to the statistical procedure are conflated with simplifications to
the likelihood functions from the experiments themselves.Comment: Further checks about accuracy of neural network approximation, fixed
typos, added refs. Main results unchanged. Matches version accepted by JHE
Data reduction in the ITMS system through a data acquisition model with self-adaptive sampling rate
Long pulse or steady state operation of fusion experiments require data acquisition and processing systems that reduce the volume of data involved. The availability of self-adaptive sampling rate systems and the use of real-time lossless data compression techniques can help solve these problems. The former is important for continuous adaptation of sampling frequency for experimental requirements. The latter allows the maintenance of continuous digitization under limited memory conditions. This can be achieved by permanent transmission of compressed data to other systems. The compacted transfer ensures the use of minimum bandwidth. This paper presents an implementation based on intelligent test and measurement system (ITMS), a data acquisition system architecture with multiprocessing capabilities that permits it to adapt the system’s sampling frequency throughout the experiment. The sampling rate can be controlled depending on the experiment’s specific requirements by using an external dc voltage signal or by defining user events through software. The system takes advantage of the high processing capabilities of the ITMS platform to implement a data reduction mechanism based in lossless data compression algorithms which are themselves based in periodic deltas
On a class of minimum contrast estimators for Gegenbauer random fields
The article introduces spatial long-range dependent models based on the
fractional difference operators associated with the Gegenbauer polynomials. The
results on consistency and asymptotic normality of a class of minimum contrast
estimators of long-range dependence parameters of the models are obtained. A
methodology to verify assumptions for consistency and asymptotic normality of
minimum contrast estimators is developed. Numerical results are presented to
confirm the theoretical findings.Comment: 23 pages, 8 figure
Structure of the lightest scalar meson from the 1/Nc expansion of Unitarized Chiral Perturbation Theory and Regge Theory
One-loop unitarized Chiral Perturbation Theory (UChPT) calculations, suggest
a different Nc behaviour for the sigma or f_0(600) and rho(770) mesons: while
the rho meson becomes narrower with Nc, as is expected for a q-qbar meson, the
sigma becomes broader, and its contribution to the total cross section is less
and less important. On the other hand, local duality requires a cancellation
between the sigma and rho amplitudes, but if there is a different Nc behaviour
for them, there is a possible contradiction between the Inverse Amplitude
Method (IAM) and local duality for large Nc. However, next to next to leading
order UChPT calculations suggested a subdominant q-qbar component for the sigma
with a mass around 1.2 GeV. In this work, we show that this subdominant q-qbar
component is indeed needed to ensure local duality.Comment: To appear in the Proceedings of the Hadron09 International
Conference. 29th Nov-4th Dec. 2009. Tallahassee, FL, USA. 5 page
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