1,093 research outputs found
Hadron multiplicities, pT-spectra and net-baryon number in central Pb+Pb collisions at the LHC
We compute the initial energy density and net baryon number density in 5%
most central Pb+Pb collisions at TeV from pQCD + (final state)
saturation, and describe the evolution of the produced system with
boost-invariant transversely expanding hydrodynamics. In addition to the total
multiplicity at midrapidity, we give predictions for the multiplicity of
charged hadrons, pions, kaons and (anti)protons, for the total transverse
energy and net-baryon number, as well as for the -spectrum of charged
hadrons, pions and kaons. We also predict the region of applicability of
hydrodynamics by comparing these results with high- hadron spectra
computed from pQCD and energy losses.Comment: 2 pages, 2 figures, to be presented at the workshop "Heavy Ion
Collisions at the LHC: Last Call for Predictions" at CERN 29 May - 2 Jun
The Effect of Shadowing on Initial Conditions, Transverse Energy and Hard Probes in Ultrarelativistic Heavy Ion Collisions
The effect of shadowing on the early state of ultrarelativistic heavy ion
collisions is investigated along with transverse energy and hard process
production, specifically Drell-Yan, , and production. We
choose several parton distributions and parameterizations of nuclear shadowing,
as well as the spatial dependence of shadowing, to study the influence of
shadowing on relevant observables. Results are presented for Au+Au collisions
at GeV and Pb+Pb collisions at TeV.Comment: Submitted to Phys. Rev.
Transverse Spectra of Hadrons in Central Collisions at RHIC and LHC from pQCD+Saturation+Hydrodynamics and from pQCD+Energy Losses
We study the transverse spectra of hadrons in nearly central collisions
at RHIC and LHC in a broad transverse momentum range Low- spectra are
calculated by using boost-invariant hydrodynamics with initial energy and
net-baryon densities from the EKRT pQCD+saturation model. High- spectra
are obtained from pQCD jet calculation including the energy loss of the parton
in the matter prior to its fragmentation to final hadrons.Comment: 4 pages, 2 figures, proceedings for Quark Matter 200
Nuclear corrections of parton distribution functions
We report global analysis results of experimental data for nuclear
structure-function ratios F_2^A/F_2^{A'} and proton-nucleus Drell-Yan
cross-section ratios sigma_{DY}^{pA}/sigma_{DY}^{pA'} in order to determine
optimum parton distribution functions (PDFs) in nuclei. An important point of
this analysis is to show uncertainties of the distributions by the Hessian
method. The results indicate that the uncertainties are large for gluon
distributions in the whole x region and for antiquark distributions at x>0.2.
We provide a code for calculating any nuclear PDFs at given x and Q^2 for
general users. They can be used for calculating high-energy nuclear reactions
including neutrino-nucleus interactions, which are discussed at this workshop.Comment: 1+6 pages, LaTeX, 10 eps files, espcrc2.sty, to be published in Nucl.
Phys. B Supplements, Proceedings of the Third International Workshop on
Neutrino-Nucleus Interactions in the Few GeV Region (NuInt04), Gran Sasso,
Italy, March 17-21, 2004. Nuclear PDF library is available at
http://hs.phys.saga-u.ac.jp/nuclp.htm
Black Hole Production at LHC: String Balls and Black Holes from pp and Lead-lead Collisions
If the fundamental planck scale is near a TeV, then parton collisions with
high enough center-of-mass energy should produce black holes. The production
rate for such black holes at LHC has been extensively studied for the case of a
proton-proton collision. In this paper, we extend this analysis to a lead-lead
collision at LHC. We find that the cross section for small black holes which
may in principle be produced in such a collision is either enhanced or
suppressed, depending upon the black hole mass. For example, for black holes
with a mass around 3 TeV we find that the differential black hole production
cross section, d\sigma/dM, in a typical lead-lead collision is up to 90 times
larger than that for black holes produced in a typical proton-proton collision.
We also discuss the cross-sections for `string ball' production in these
collisions. For string balls of mass about 1 (2) TeV, we find that the
differential production cross section in a typical lead-lead collision may be
enhanced by a factor up to 3300 (850) times that of a proton-proton collision
at LHC.Comment: Added some discussion, final version to appear in Phys. Rev. D (rapid
communications
Prompt Photon and Inclusive Production at RHIC and LHC
We present results for prompt photon and inclusive production in p-p
and A-A collisions at RHIC and LHC energies. We include the full
next-to-leading order radiative corrections and nuclear effects, such as
nuclear shadowing and parton energy loss. We find the next-to-leading order
corrections to be large and dependent. We show how measurements of
production at RHIC and LHC, at large , can provide valuable
information about the nature of parton energy loss.
We calculate the ratio of prompt photons to neutral pions and show that at
RHIC energies this ratio increases with approaching one at
GeV, due to the large suppression of production. We show that at the
LHC, this ratio has steep dependence and approaches 10% effect at GeV.Comment: Talk presented by I. Sarcevic, to appear in the Proceedings of Quark
Matter 2002; 4 pages including 4 color figure
DGLAP analyses of nPDF: constraints from data
We explain how the constraints from present experimental data can be used to
obtain the nPDF in the framework of LO DGLAP evolution. We will also compare
the only two available sets of this type and comment on the important
information that neutrino factories could provide.Comment: 1 pages, 1 postscript figure. Invited talk at the NuFact'02 workshop
(Neutrino Factories based on Muon Storage Rings), London, July 200
Angular pattern of minijet transverse energy flow in hadron and nuclear collisions
The azimuthal asymmetry of minijet system produced at the early stage of
nucleon-nucleon and nuclear collisions in a central rapidity window is studied.
We show that in pp collisions the minijet transverse energy production in a
central rapidity window is essentially unbalanced in azimuth due to asymmetric
contributions in which only one minijet hits the acceptance window. We further
study the angular pattern of transverse energy flow generated by semihard
degrees of freedom at the early stage of high energy nuclear collisions and its
dependence on the number of semihard collisions in the models both including
and neglecting soft contributions to the inelastic cross section at RHIC and
LHC energies as well as on the choice of the infrared cutoff.Comment: 25 LaTeX pages, 11 figures embedded with epsf; expanded versio
Skyrme model and Isospin Chemical Potential
We discuss the stability of the Skyrmion solution in the presence of a finite
isospin chemical potential . Solving numerically the mass of the Skyrmion
as function of , we find a critical value MeV where the
Skyrmion mass vanishes. We compare the exact numerical treatment with an
analytical discussion based on a special shape for the profile of the Skyrmion
due to Atiyah and Manton. The extension of this ansatz for finite works
quite well for MeV. Then, for small values of , where the
analytical approach is valid, we consider the possibility of having an angular
deformation for the Skyrmionic profile, which is possible for finite values of
. This is however, a small effect. Finally we introduce finite temperature
corrections, which strength the instability induced by the chemical potential,
finding the dependence of the critical temperature on .Comment: 13 pages, 7 figure
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