206 research outputs found
Conservation Laws and Particle Production in Heavy Ion Collisions
We discuss the role of the conservation laws related with U(1) internal
symmetry group in the statistical model description of particle productions in
ultrarelativistic heavy ion collisions. We derive and show the differences in
particle multiplicities in the canonical and the grand canonical formulation of
quantum number conservation. The time evolution and the approach to chemical
equilibrium in the above ensembles is discussed in terms of kinetic master
equation. The application of the statistical model to the description of
(multi)strange particle yields at GSI/SIS and the SPS energies is also
presented.Comment: Invited talk at International Symposium on Hadron and Nuclei, Seoul,
Korea, 20-22 Feb 200
Comparison of Chemical Freeze-Out Criteria in Heavy-Ion Collisions
One of the most remarkable results to emerge from heavy-ion collisions over
the past two decades is the striking regularity shown by particle yields at all
energies. This has led to several very successful proposals describing particle
yields over a very wide range of beam energies, reaching from 1 A GeV up to 200
A GeV, using only one or two parameters. A systematic comparison of these
proposals is presented here. The conditions of fixed energy per particle,
baryon+anti-baryon density, normalized entropy density as well as percolation
model are investigated. The results are compared with the most recent chemical
freeze-out parameters obtained in the thermal-statistical analysis of particle
yields. The sensitivity and dependence of the results on parameters is analyzed
and discussed. It is shown that in the energy range above the top AGS energy,
within present accuracies, all chemical freeze-out criteria give a fairly good
description of the particle yields. However, the low energy heavy-ion data
favor the constant energy per particle as a unified condition of chemical
particle freeze-out. This condition also shows the weakest sensitivity on model
assumptions and parameters.Comment: 15 pages 7 figures uses revte
Real-time Monitoring of High-speed Spindle Operations Using Infrared Data Transmission
AbstractHigh-performance cutting is carried out with high cutting and feed speeds. Particularly, the use of heavy cutting tools (e.g. in planing machines), it is important to monitor the clamping and balance condition of the mounted tool, as well as the process forces. Therefore, a real-time monitoring system for high-speed operations based on the IrDA protocol was developed. It could be shown that infrared data transmission systems allow shorter reaction times compared to conventional wireless LAN applications. The presented monitoring system provides a reaction time of 7.14 ms at a bandwidth of 42.5 kHz and a data rate of 4.1 MBit/s
Is soft physics entropy driven?
The soft physics, pT < 2 GeV/c, observables at both RHIC and the SPS have now
been mapped out in quite specific detail. From these results there is mounting
evidence that this regime is primarily driven by the multiplicity per unit
rapidity, dNch/deta. This suggests that the entropy of the system alone is the
underlying driving force for many of the global observables measured in
heavy-ion collisions. That this is the case and there is an apparent
independence on collision energy is surprising. I present the evidence for this
multiplicity scaling and use it to make some extremely naive predictions for
the soft sector results at the LHC.Comment: Proceedings of Hot Quarks 2006. 8 figures, 6 page
Strangeness, Charm and Beauty in Quark Matter: SQM 2007 Experimental Overview
This paper aims at providing an experimental overview of the Strangeness in
Quark Matter 2007 ConferenceComment: Proceedings of Strangeness in Quark Matter 2007, submitted to Journal
of Physics
Relativistic Nucleus-Nucleus Collisions: from the BEVALAC to RHIC
I briefly describe the initial goals of relativistic nuclear collisions
research, focusing on the LBL Bevatron/Bevalac facility in the 1970's. An early
concept of high hadronic density fireball formation, and subsequent isentropic
decay (preserving information as to the high density stage) led to an outline
of physics observables that could determine the nuclear matter equation of
state at several times nuclear ground state matter density. With the advent of
QCD the goal of locating, and characterizing the hadron-parton deconfinement
phase transformation suggested the need for higher , the research
thus moving to the BNL AGS and CERN SPS, finally to RHIC at BNL. A set of
physics observables is discussed where present data span the entire
domain, from Bevalac and SIS at GSI, to top RHIC energy. Referring,
selectively, to data concerning bulk hadron production, the overall
evolution of directed and radial flow observables, and of pion pair
Bose-Einstein correlation are discussed. The hadronization process is studied
in the grand canonical statistical model. The resulting hadronization points in
the plane T vs. converge onto the parton-hadron phase boundary
predicted by finite lattice QCD, from top SPS to RHIC energy. At lower
SPS and top AGS energy a steep strangeness maximum occurs at which the
Wroblewski parameter 0.6; a possible connection to the QCD
critical point is discussed. Finally the unique new RHIC physics is addressed:
high hadron suppression and jet "tomography".Comment: 19 pages, 11 figure
Chemical equilibration of strangeness
Thermal models are very useful in the understanding of particle production in
general and especially in the case of strangeness. We summarize the assumptions
which go into a thermal model calculation and which differ in the application
of various groups. We compare the different results to each other. Using our
own calculation we discuss the validity of the thermal model and the amount of
strangeness equilibration at CERN-SPS energies. Finally the implications of the
thermal analysis on the reaction dynamics are discussed.Comment: 23 pages, LaTeX (figures included); Talk given at the Int. Symposium
on Strangeness in Quark Matter 1997, Santorini (Greece), April 199
Strangeness Conservation in Hot Nuclear Fireballs
A constraint between thermal fireball parameters arises from the requirement
that the balance of strangeness in a fireball is (nearly) zero. We study the
impact of this constraint on (multi-)strange (anti-)baryon multiplicities and
compare the hadron gas and quark-gluon plasma predictions. We explore the
relation between the entropy content and particle multiplicities and show that
the data are compatible with the quark-gluon plasma hypothesis, but appear to
be inconsistent with the picture of an equilibrated hadron gas fireball. We
consider the implications of the results on the dynamics of evolution and decay
of the particle source.Comment: 35 pages, 11 postscript figures, report PAR/LPTHE/92--2
Genetic diversity in Tunisian horse breeds
This study aimed at screening genetic diversity and differentiation
in four horse breeds raised in Tunisia, the Barb, Arab-Barb, Arabian, and
English Thoroughbred breeds. A total of 200 blood samples (50 for each breed)
were collected from the jugular veins of animals, and genomic DNA was
extracted. The analysis of the genetic structure was carried out using a
panel of 16 microsatellite loci. Results showed that all studied
microsatellite markers were highly polymorphic in all breeds. Overall, a
total of 147 alleles were detected using the 16 microsatellite loci. The
average number of alleles per locus was 7.52 (0.49), 7.35 (0.54), 6.3 (0.44),
and 6 (0.38) for the Arab-Barb, Barb, Arabian, and English Thoroughbred
breeds, respectively. The observed heterozygosities ranged from 0.63 (0.03)
in the English Thoroughbred to 0.72 in the Arab-Barb breeds, whereas the
expected heterozygosities were between 0.68 (0.02) in the English
Thoroughbred and 0.73 in the Barb breeds. All FST values calculated by pairwise breed combinations were significantly different from zero
(p < 0.05) and an important genetic differentiation among breeds was
revealed. Genetic distances, the factorial correspondence, and principal
coordinate analyses showed that the important amount of genetic variation was
within population. These results may facilitate conservation programs for the
studied breeds and enhance preserve their genetic diversity
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