4,966 research outputs found
Total Cross-sections
We examine the energy dependence of total cross-sections for photon processes
and discuss the QCD contribution to the rising behaviourComment: 5 pages, LaTeX, 2 figures, talk presented by G. Pancheri at Photon -
2001, The International Conference on Structure and Interactions of Photons,
Ascona, Sept. 2-7,2001. To appear in the proceeding
Total Photonic and Hadronic Cross-sections
We discuss total cross-sections within the context of the QCD calculable
mini-jet model, highlighting its successes and failures. In particular we show
its description of and compare it with OPAL and L3
data. We extrapolate this result to total cross-sections and propose
a phenomenological ans\"atz for virtual photon cross-sections. We point out
that the good agreement with data obtained with the Eikonal Minijet Model
should not hide the many uncertainties buried in the impact parameter
distribution. A model obtained from Soft Gluon Summation is briefly discussed
and its application to hadronic cross-sections is shown.Comment: 10 pages, 5 figures, LaTeX, uses aipproc.sty. To appear in the
proceedings of Photon 2000, Ambelside, U.K., Aug 2000. The title, the number
of pages and the number of figures in the announcement were corrected to
correspond to the submitted pape
QCD and Total Cross-sections
We discuss models for total cross-sections, show their predictions for
photon-photon collisions and compare them with the recent LEP measurements. We
show that the extrapolations to high center of mass energies within various
models differ by large factors at high energies and discuss the precision
required from future measurements at the proposed Linear Collider which would
allow to distinguish between them.Comment: 7 pages, 4 figures, laTeX, requires sprocl.sty, added at the end. To
appear in the Proceedings of XXIX International Symposium on Mutliparticle
Dynamics, Brwon University, U.S.A., June 9
Total Cross Sections
A unified approach to total cross-sections, based on the QCD contribution to
the rise with energy, is presented for the processes , , . For proton processes, a discussion of
the role played by soft gluon summation in taming the fast rise due to
mini-jets is presented. For photon-photon processes, a comparison with other
models indicates the need for precision measurements in both the low and high
energy region, likely only with measurements at future Linear Colliders.Comment: 15 pages, 9 figures, LaTeX, uses hsproc.sty and art10.sty. Talk given
by G. Pancheri at 'International Hadron Structure-2000', October 1-6,
Staralesn
Total Cross-sections and Bloch-Nordsieck Gluon Resummation
The physics underlying the fall and eventual rise in various total
cross-sections at high energies has been investigated over a decade using a
model based on the Bloch-Nordsieck resummation in QCD. Here a brief review of
our latest results is presented and comparison made with experimental data on
, and total cross-sections.Comment: Presented by G. Pancheri at ISMD04, Sonoma State University. Under
publication in Acta Physica Polonica. LaTeX format, 10 *.eps files, 7 page
Total Cross-sections at very high energies: from protons to photons
A model for both proton and photon total cross-sections is presented and
compared with data. The model is based on the eikonal representation, with QCD
mini-jets to drive the rise and soft gluon kt-resummation into the Infrared
region to tame the excessive rise due to low-x perturbative gluons. We discuss
the effects of a singular but integrable expression for the Infrared gluon
spectrum on the high energy behaviour of the total cross-section expected in
this model.Comment: 13 pages, 4 figures, Tenth Workshop on Non-Perturbative Quantum
Chromodynamics at l'Institut Astrophysique de Paris, June 8-12, 200
Total cross sections and soft gluon resummation
We discuss a model for total hadronic and photonic cross-sections which
includes hard parton-parton scattering to drive the rise and soft gluon
resummation to tame it. Unitarity is ensured by embedding the cross-section in
the eikonal formalism. Predictions for LHC and ILC are presented.Comment: 9 pages, 2 figures, Presented at PLC2005, Kazimierz, September 2005,
requires appolb.cl
Predictions for the total cross-section in the TeV region: an update
In this talk we present an update of model predictions for the total cross-section in the TeV region. The update includes preliminary
results for cross-sections using the Bloch-Nordsieck model for
the overlap function of the partons in the transverse space, use of the CJLK
parametrisation of the photonic parton densities that has recently become
available and extension to the higher energies relevant to the
planned CLIC collider.Comment: Talk presented by A. De Roeck at the International Linear Collider
Workshop, Jeju Island, Aug. 26-30,2002. To appear in the proceedings. 10
pages, LaTeX file, requires A4.sty, four figure
Total cross-section at LHC from minijets and soft gluon resummation in the infrared region
A model for total cross-sections incorporating QCD jet cross-sections and
soft gluon resummation is described and compared with present data on and
cross-sections. Predictions for LHC are presented for different
parameter sets. It is shown that they differ according to the small x-behaviour
of available parton density functions.Comment: 10 pages, 3 figures, uses appolb.cls, LaTeX. Talk presented by G.
Pancheri at the EURIDICE Final Meeting, August 24-27th, 2006, Kazimierz,
Polan
Complex networks in brain electrical activity
We analyze the complex networks associated with brain electrical activity.
Multichannel EEG measurements are first processed to obtain 3D voxel
activations using the tomographic algorithm LORETA. Then, the correlation of
the current intensity activation between voxel pairs is computed to produce a
voxel cross-correlation coefficient matrix. Using several correlation
thresholds, the cross-correlation matrix is then transformed into a network
connectivity matrix and analyzed. To study a specific example, we selected data
from an earlier experiment focusing on the MMN brain wave. The resulting
analysis highlights significant differences between the spatial activations
associated with Standard and Deviant tones, with interesting physiological
implications. When compared to random data networks, physiological networks are
more connected, with longer links and shorter path lengths. Furthermore, as
compared to the Deviant case, Standard data networks are more connected, with
longer links and shorter path lengths--i.e., with a stronger ``small worlds''
character. The comparison between both networks shows that areas known to be
activated in the MMN wave are connected. In particular, the analysis supports
the idea that supra-temporal and inferior frontal data work together in the
processing of the differences between sounds by highlighting an increased
connectivity in the response to a novel sound.Comment: 22 pages, 5 figures. Starlab preprint. This version is an attempt to
include better figures (no content change
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