2,342 research outputs found
Heavy-ion physics at the LHC
A color-deconfined state of strongly interacting matter is expected to be formed in high-energy collisions of heavy nuclei. Lattice Quantum Chromodynamics (QCD) calculations predicts that, under the conditions of high-energy density
and temperature reached in these collisions, a phase transition to a Quark-Gluon Plasma (QGP) occurs. The main aim of the heavy-ion experimental programme at the LHC collider is to characterize and study the medium formed in such collisions. In this paper several observables and measurements performed by the LHC experiments studying heavy-ion collisions will be addressed, compared to results at lower energy and discussed
Measurement of the electromagnetic dissociation cross section of Pb nuclei at = 2.76 TeV
Electromagnetic dissociation of heavy nuclei in ultra-peripheral interactions
at high energies can be used to monitor the beam luminosity at colliders. In
ALICE neutrons emitted by the excited nuclei close to beam rapidity are
detected by the Zero Degree Calorimeters (ZDCs), providing a precise
measurement of the event rate. During the 2010 Pb run, a dedicated data taking
was performed triggering on electromagnetic processes with the ZDCs. These
data, combined with the results from a Van der Meer scan, allowed to measure
the electromagnetic dissociation cross-section of Pb nuclei at ~=~2.76~TeV. Experimental results on various cross-sections are presented
together with a comparison to the available predictions.Comment: 4 pages, 3 figure
Bulk Properties of Pb-Pb collisions at sqrt(sNN) = 2.76 TeV measured by ALICE
Global variables, such as the charged particle multiplicity and the
transverse energy are important observables to characterize Relativistic Heavy
Ion collisions and to constrain model calculations. The charged particle
multiplicity dNch/deta and transverse energy dET/deta are measured at sqrt(sNN)
= 2.76 TeV in Pb-Pb collisions as a function of centrality and in pp
collisions. The fraction of inelastic cross section seen by the ALICE detector
is calculated either using a Glauber model or the data corrected by simulations
of nuclear and electromagnetic processes, or data collected with a minimum bias
interaction trigger. The centrality, defined by the number of nucleons
participating in the collision, is obtained, via the Glauber model, by relating
the multiplicity distributions of various detectors in the ALICE Central Barrel
and their correlation with the spectator energy measured by the Zero-Degree
Calorimeters. The results are compared to corresponding results obtained at the
significantly lower energies of the BNL AGS, the CERN SPS, and the BNL RHIC,
and with models based on different mechanisms for particle production in
nuclear collisions. Particular emphasis will be given to a discussion on
systematic studies of the dependence of the centrality determination on the
details of the Glauber model, and the validity of the Glauber model at
unprecedented collision energies.Comment: Proceedings of the XXII International Conference on Ultrarelativistic
Nucleus-Nucleus Collisions Quark Matter 2011, submitted to J. Phys. G: Nucl.
Part. Phys. 8 pages, 7 (multi)figure
Channeler Ant Model: 3D segmentation of medical images through ant colonies
In this paper the Channeler Ant Model (CAM) and some results
of its applications to the analysis of medical images are described. The CAM is an algorithm able to segment 3D structures with different shapes, intensity and background.
It makes use of virtual ant colonies and exploits their natural capabilities to modify the environment and communicate with each other by pheromone deposition. Its performance has been validated with the segmentation of 3D artificial objects and it has been already used successfully in lung nodules detection on Computer
Tomography images. This work tries to evaluate the CAM as a candidate to solve the quantitative segmentation problem in Magnetic Resonance brain images: to evaluate the percentage of white matter, gray matter and cerebrospinal fluid in
each voxel
Study of dimuon production in Indium-Indium collisions with the NA60 experiment
The NA60 experiment at the CERN-SPS is devoted to the study of dimuon
production in heavy-ion and proton-nucleus collisions. We present preliminary
results from the analysis of Indium-Indium collisions at 158 GeV per nucleon.
The topics covered are low mass vector meson production, J/psi production and
suppression, and the feasibility of the open charm measurement from the dimuon
continuum in the mass range below the J/psi peak.Comment: Contribution at XXXXth Rencontres de Moriond, "QCD and High Energy
Hadronic Interactions
First results from the NA60 experiment at CERN
Since 1986, several heavy ion experiments have studied some signatures of the
formation of the quark-gluon plasma and a few exciting results have been found.
However, some important questions are still unanswered and require new
measurements. The NA60 experiment, with a new detector concept that vastly
improves dimuon detection in proton-nucleus and heavy-ion collisions, studies
several of those open questions, including the production of open charm. This
paper presents the experiment and some first results from data collected in
2002.Comment: Paper presented at the XXXVIII Rencontres de Moriond, QCD and High
Energy Hadronic Interactions, Les Arcs, March 22-29, 2003. 4 pages, 6 figure
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