49 research outputs found
Jet Transport Coefficient at the Large Hadron Collider Energies in a Color String Percolation Approach
Within the color string percolation model (CSPM), jet transport coefficient,
, is calculated for various multiplicity classes in proton-proton and
for centrality classes in nucleus-nucleus collisions at the Large Hadron
Collider energies for a better understanding of the matter formed in
ultra-relativistic collisions. is studied as a function of final
state charged particle multiplicity, initial state percolation temperature and
energy density. The CSPM results are then compared with different theoretical
calculations from the JET collaboration those incorporate particle energy loss
in the medium. A good agreement is found between CSPM results and the JET
collaboration calculations.Comment: 8 pages and 7 figures, Submitted for publicatio
Formation of a Perfect Fluid in , -Pb, Xe-Xe and Pb-Pb Collisions at the Large Hadron Collider Energies
Isothermal compressibility () is an important thermodynamic
observable which gives information about the deviation of a fluid from a
perfect fluid. In this work, for the first time we have estimated the
isothermal compressibility of QCD matter formed in high energy hadronic and
nuclear collisions using color string percolation model (CSPM), where we
investigate the change in as a function of final state charged
particle multiplicity across various collision species. We have also estimated
the initial percolation temperature for different collision systems at
different collision energies, which helps us to have a better understanding of
the system at the initial phase of evolution. The comparison of the CSPM
results for isothermal compressibility with that for the well known fluids,
indicates that the matter formed in heavy-ion collisions might be the {\it
closest perfect fluid} found in nature. This estimation complements the
well-known observation of minimum shear viscosity to entropy density ratio for
a possible QGP medium created in heavy-ion collision experiments. Also, a
threshold of pseudorapidity density of charged particles, is found for a possible QGP formation at the LHC energies.Comment: Xe-Xe data are added to this versio
Searching for the Next Yukawa Phase of QCD
QCD predicts that the interactions between quarks and gluons change from a
confining to a screened Yukawa form above a critical temperature
MeV. In this talk, I review some of the key observables in heavy ion reactions
which are being used to search for this new partonic Yukawa phase at SPS and
RHIC. These include collective observables such as ,
meson interferometry, jet quenching, and suppression.Comment: 24 pages (PTPTex style files included) with 26 eps,ps figures using
epsf,psfig. To appear in Proc. of 14th Nishinomiya-Yukawa Memorial Symposium
Nov. 1999, Japan; updated with a critique of the CERN press release Feb. 8,
200
Particle Production in Heavy Ion Collisions
The status of thermal model descriptions of particle production in heavy ion
collisions is presented. We discuss the formulation of statistical models with
different implementation of the conservation laws and indicate their
applicability in heavy ion and elementary particle collisions. We analyze
experimental data on hadronic abundances obtained in ultrarelativistic heavy
ion collisions, in a very broad energy range starting from RHIC/BNL ( A GeV), SPS/CERN ( A GeV) up to AGS/BNL ( A GeV) and SIS/GSI ( A GeV) to test equilibration
of the fireball created in the collision. We argue that the statistical
approach provides a very satisfactory description of experimental data covering
this wide energy range. Any deviations of the model predictions from the data
are indicated. We discuss the unified description of particle chemical
freeze--out and the excitation functions of different particle species. At SPS
and RHIC energy the relation of freeze--out parameters with the QCD phase
boundary is analyzed. Furthermore, the application of the extended statistical
model to quantitative understanding of open and hidden charm hadron yields is
considered.Comment: Invited review for Quark Gluon Plasma 3, eds. R. C. Hwa and Xin-Nian
Wang, World Scientific Publishin
Heavy-flavour and quarkonium production in the LHC era: from proton-proton to heavy-ion collisions
This report reviews the study of open heavy-flavour and quarkonium production
in high-energy hadronic collisions, as tools to investigate fundamental aspects
of Quantum Chromodynamics, from the proton and nucleus structure at high energy
to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is
given to the lessons learnt from LHC Run 1 results, which are reviewed in a
global picture with the results from SPS and RHIC at lower energies, as well as
to the questions to be addressed in the future. The report covers heavy flavour
and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus
collisions. This includes discussion of the effects of hot and cold strongly
interacting matter, quarkonium photo-production in nucleus-nucleus collisions
and perspectives on the study of heavy flavour and quarkonium with upgrades of
existing experiments and new experiments. The report results from the activity
of the SaporeGravis network of the I3 Hadron Physics programme of the European
Union 7th Framework Programme
Phase transitions in the early and the present Universe
The evolution of the Universe is the ultimate laboratory to study fundamental
physics across energy scales that span about 25 orders of magnitude: from the
grand unification scale through particle and nuclear physics scales down to the
scale of atomic physics. The standard models of cosmology and particle physics
provide the basic understanding of the early and present Universe and predict a
series of phase transitions that occurred in succession during the expansion
and cooling history of the Universe. We survey these phase transitions,
highlighting the equilibrium and non-equilibrium effects as well as their
observational and cosmological consequences. We discuss the current theoretical
and experimental programs to study phase transitions in QCD and nuclear matter
in accelerators along with the new results on novel states of matter as well as
on multi- fragmentation in nuclear matter. A critical assessment of
similarities and differences between the conditions in the early universe and
those in ultra- relativistic heavy ion collisions is presented. Cosmological
observations and accelerator experiments are converging towards an
unprecedented understanding of the early and present Universe.Comment: 41 pages, 16 figures, to appear in Ann. Rev. Nucl. Part. Sci 2006.
Presentation improved, references adde