927 research outputs found
Generalisation of DGLAP equations to massive partons
DGLAP evolution equations are modified in order to use all the quark families
in the full scale range, satisfying kinematical constraints and sumrules, thus
having complete continuity for the pdfs and observables. Some consequences of
this new approach are shown.Comment: 12 Pages and 5 Figure
A fast and precise method to solve the Altarelli-Parisi equations in x space
A numerical method to solve linear integro-differential equations is
presented. This method has been used to solve the QCD Altarelli-Parisi
evolution equations within the H1 Collaboration at DESY-Hamburg. Mathematical
aspects and numerical approximations are described. The precision of the method
is discussed.Comment: 18 pages, 4 figure
A new global analysis of deep inelastic scattering data
A new QCD analysis of Deep Inelastic Scattering (DIS) data is presented. All
available neutrino and anti-neutrino cross sections are reanalysed and included
in the fit, along with charged-lepton DIS and Drell-Yan data. A massive
factorisation scheme is used to describe the charm component of the structure
functions. Next-to-leading order parton distribution functions are provided. In
particular, the strange sea density is determined with a higher accuracy with
respect to other global fits.Comment: 51 pages, 18 figure
Error Estimates on Parton Density Distributions
Error estimates on parton density distributions are presently based on the
traditional method of least squares minimisation and linear error propagation
in global QCD fits. We review the underlying assumptions and the various
mathematical representations of the method and address some technical issues
encountered in such a global analysis. Parton distribution sets which contain
error information are described.Comment: Latex, 12 pages, 5 figures. Needs iopart.cls and iopart12.clo.
Presented at New Trends in HERA Physics 2001, Ringberg Castle, Tegernsee,
Germany, June 17-22, 200
Combined HERA Deep Inelastic Scattering Data and NLO QCD Fits
Previously published data on inclusive neutral and charged current e+p and
e-p deep inelastic scattering from HERA have been combined. The new,
model-independent method of combining the measured cross sections takes full
account of correlated systematics in a coherent way, leading to significantly
reduced uncertainties in the combined measurement across the (x, Q^2) plane.
The combined cross section data have been used as the sole input for a new
next-to-leading order QCD fit to extract the parton distribution functions
(PDFs) of the proton. The PDFs extracted have greatly reduced experimental
uncertainties, compared to separate QCD analyses on data from H1 and ZEUS.
Model uncertainties, including those arising from the parameterisation
dependence, have also been carefully considered. The resulting HERA PDFs have
impressive precision.Comment: 11 pages, 6 figures, prepared for the proceedings of the Ringberg
Workshop on "New Trends in HERA Physics 2008", Ringberg Castle, Tegernsee,
Oct 5-10, 200
Transmission through quantum networks
We propose a simple formalism to calculate the conductance of any quantum
network made of one-dimensional quantum wires. We apply this method to analyze,
for two periodic systems, the modulation of this conductance with respect to
the magnetic field. We also study the influence of an elastic disorder on the
periodicity of the AB oscillations and we show that a recently proposed
localization mechanism induced by the magnetic field resists to such a
perturbation. Finally, we discuss the relevance of this approach for the
understanding of a recent experiment on GaAs/GaAlAs networks.Comment: 4 pages, 5 EPS figure
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