4,617 research outputs found
Multiplicities and Transverse Energies in Central AA Collisions at RHIC and LHC from pQCD, Saturation and Hydrodynamics
We compute the particle multiplicities and transverse energies at central and
nearly central AA collisions at RHIC and LHC. The initial state is computed
from perturbative QCD supplemented by the conjecture of saturation of produced
partons. The expansion stage is described in terms of hydrodynamics assuming
longitudinal boost invariance and azimuthal symmetry. Transverse flow effects,
a realistic list of hadrons and resonance decays are included. Comparison with
the data of the multiplicities at AGeV and 130 AGeV from RHIC is
done and predictions for the full RHIC energy and LHC energy are made for the
multiplicities and transverse energies. The reduction from the initially
released minijet transverse energy to the in the final state is less than
in the one-dimensional case but still dramatic: a factor of 2.7 at RHIC, and
3.6 at the LHC.Comment: The results for LHC have been correcte
Multiplicities for LHC Nuclear Collisions Using HERA Structure Functions
We compute in QCD perturbation theory the transverse energy carried by
gluons, quarks and antiquarks with GeV in Pb+Pb
collisions at GeV by using structure functions compatible
with the small- increase observed at HERA. This gives a perturbative
estimate for the energy and entropy density of the bulk system at times
fm. The predicted initial gluon entropy density gives a lower
limit of about 2200...3400 for the final charged multiplicity. Sources of
further entropy increase are discussed.Comment: HU-TFT-94-6, 7 pages, 3 PostScript figures included in the end of the
tex-fil
Transverse spectra of hadrons at RHIC
We present results on spectra of pions, kaons and (anti)protons from a study
of heavy ion collisions using the perturbative QCD + saturation model to
calculate the production of initial (transverse) energy and baryon number
followed by a hydrodynamic description of the expansion of produced matter. In
particular, we study how the hadron spectra and multiplicities depend on the
decoupling temperature \Tdec when the low temperature phase contains all
hadrons and and hadron resonances with mass below 2 GeV. We show that the
spectra and multiplicities of pions, kaons and (anti)protons measured at RHIC
in central Au+Au collisions with GeV can be obtained with a
single decoupling temperature 150160 MeV, common for both the chemical and
the kinetic freeze-out.Comment: 4 pages, 2 eps-figures, talk at Quark Matter '02, Nantes, France,
July 200
EPS09 - Nuclear PDFs and Their Uncertainties at NLO
In this talk, we present our recent next-to-leading order (NLO) nuclear
parton distribution functions (nPDFs), which we call EPS09. As an extension to
earlier NLO analyses, we supplement the deep inelastic scattering and Drell-Yan
dilepton data by inclusive midrapidity pion measurements from RHIC in order to
reduce the otherwize large freedom in the nuclear gluon densities. Our
Hessian-type error analysis leading to a collection of nPDF error sets, is the
first of its kind among the nPDF analyses.Comment: 4 pages, 4 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
Scaling of transverse energies and multiplicities with atomic number and energy in ultrarelativistic nuclear collisions
We compute how the initial energy density and produced gluon, quark and
antiquark numbers scale with atomic number and beam energy in ultrarelativistic
heavy ion collisions. The computation is based on the argument that the effect
of all momentum scales can be estimated by performing the computation at one
transverse momentum scale, the saturation momentum. The initial numbers are
converted to final ones by assuming kinetic thermalisation and adiabatic
expansion. The main emphasis of the study is at LHC and RHIC energies but it is
observed that even at SPS energies this approach leads to results which are not
unreasonable: what is usually described as a completely soft nonperturbative
process can also be described in terms of gluons and quarks. The key element is
the use of the saturation scale.Comment: 13 pages, includes 7 eps-figure
Centrality dependence of multiplicity, transverse energy, and elliptic flow from hydrodynamics
The centrality dependence of the charged multiplicity, transverse energy, and
elliptic flow coefficient is studied in a hydrodynamic model, using a variety
of different initializations which model the initial energy or entropy
production process as a hard or soft process, respectively. While the charged
multiplicity depends strongly on the chosen initialization, the p_t-integrated
elliptic flow for charged particles as a function of charged particle
multiplicity and the p_t-differential elliptic flow for charged particles in
minimum bias events turn out to be almost independent of the initial energy
density profile.Comment: 11 pages RevTex, including 10 postscript figures. Slightly modified
discussion of Figs. 5 and 6, updated references. This version to appear in
Nuclear Physics
Structure functions and parton distributions
In this talk, I review the status of theoretical understanding of nuclear
structure functions and parton distributions and discuss the constraints on
nuclear parton distributions from existing data and the global QCD analysis.Comment: Latex, 10 pages, to appear in the proceedings of QM200
High Energy Nuclear Collisions
Highlights of the results from ultrarelativistic heavy ion collisions at
CERN-SPS are reviewed. In particular, I discuss how the experimental results
indicate that a collective strongly interacting system has been produced, and
what are the implications towards the Quark Gluon Plasma. The physical ideas
behind measuring certain observables are introduced. The future program of high
energy nuclear collisions at BNL-RHIC and CERN-LHC/ALICE is also briefly
discussed.Comment: Plenary talk at the International Europhysics Conference on High
Energy Physics, EPS-HEP99, Tampere, Finland, July 1999; 21 page
Minijets in ultrarelativistic heavy ion collisions at future colliders
The role of minijet production as initial conditions for QGP production at
in nuclear collisions at the LHC and RHIC energies is
discussed.Comment: 15 pages, including 2 figures, an invited article to Comments on
Nuclear and Particle Physic
On predictions of the first results from RHIC
In this talk, I will discuss the predictions of the first results from RHIC:
the charged particle multiplicity , its centrality
dependence and the elliptic flow .Comment: A plenary review talk at Quark Matter 2001, Stony Brook, USA, January
2001, 10 page
- âŠ