313 research outputs found
Centrality dependence of the multiplicity and transverse momentum distributions at RHIC and LHC and the percolation of strings
The dependence of the multiplicity and the transverse momentum distribution
on the number of collisions are studied for central and peripheral Au-Au
collisions at SPS, RHIC and LHC energies in the framework of percolation of
strings. A scaling law relating the multiplicity to the mean transverse
momentum is obtained. Our results are in overall agreement with the SPS and
RHIC data, obtaining a suppression on distribution even for larger
than 1 GeV/c.Comment: Contribution to QM2002, espcrc1.st
Investigation of high p events in Nucleus-Nucleus collisions using the Hijing event generator
In recent years lot of interest has been observed in the nucleus-nucleus
collisions at RHIC energies in phenomena related to high physics
\cite{ref1}. The suppression of high particles and disappearance of
back-to-back jets compared to the scaling with number of binary nucleon-nucleon
collisions indicates that a nearly perfect liquid is produced in these
collisions. Results on self shadowing of high events are presented
using hadron multiplicity associated to high and unbiased events in
nucleus-nucleus collisions \cite{ref2} obtained from the hijing event
generator.Comment: 4 pages, 3 figures, Proceedings of the poster presented at Quark
Matter 200
Study of Cronin effect and nuclear modification of strange particles in d-Au and Au-Au collisions at 200 GeV in PHENIX
Effects of strangeness on nuclear modification in d-Au and Au-Au collisions
at 200 GeV are studied, in order to quantify the effects of quark content and
mass. Measurements of ratios of the yields in central collisions to the yields
in peripheral collisions are performed for lambda baryon and phi meson. Found
results show little dependence of particle suppression or enhancement on mass
and strange content, but rather prominent difference in nuclear modification
between mesons and baryons.Comment: 4 pages, 4 figures, proceedings of the Seventeenth International
Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter
2004
Beam-Energy and System-Size Dependence of Dynamical Net Charge Fluctuations
We present measurements of net charge fluctuations in collisions at
19.6, 62.4, 130, and 200 GeV, collisions at
62.4, 200 GeV, and collisions at 200
GeV using the net charge dynamical fluctuations measure . The
dynamical fluctuations are non-zero at all energies and exhibit a rather modest
dependence on beam energy. We find that at a given energy and collision system,
net charge dynamical fluctuations violate scaling, but display
approximate scaling. We observe strong dependence of dynamical
fluctuations on the azimuthal angular range and pseudorapidity widths.Comment: 4 pages, 4 figures, presented at the 19th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur,
India, February 4-10, 200
Relativistic Heavy-Ion Physics: Experimental Overview
The field of relativistic heavy-ion physics is reviewed with emphasis on new
results and highlights from the first run of the Relativistic Heavy-Ion
Collider at BNL and the 15 year research programme at the SPS at CERN and the
AGS at BNL.Comment: 15 pages, 9 figures. Invited Talk at the Fourth International
Conference on Physics and Astrophysics of Quark Gluon Plasma, (ICPAQGP-2001)
Jaipur, India, November 26-30, 200
Direct photons measured by the PHENIX experiment at RHIC
Results from the PHENIX experiment at RHIC on direct photon production in
p+p, d+Au, and Au+Au collisions at sqrt(s_NN) = 200 GeV are presented. In p+p
collisions, direct photon production at high p_T behaves as expected from
perturbative QCD calculations. The p+p measurement serves as a baseline for
direct photon production in Au+Au collisions. In d+Au collisions, no effects of
cold nuclear matter are found within the large uncertainty of the measurement.
In Au+Au collisions, the production of high p_T direct photons scales as
expected for particle production in hard scatterings. This supports jet
quenching models, which attribute the suppression of high p_T hadrons to the
energy loss of fast partons in the medium produced in the collision. Low p_T
direct photons, measured via e+e- pairs with small invariant mass, are possibly
related to the production of thermal direct photons.Comment: 5 pages, 5 figures, Proceedings of the Hot Quarks 2006 Workshop for
young scientists on the physics of ultra-relativistic nucleus-nucleus
collisions, Villasimius, Sardinia, Italy, May 15--20, 200
Quenching of High pT Hadron Spectra by Hadronic Interactions in Heavy Ion Collisions at RHIC
Typically the materialization of high energetic transverse partons to
hadronic jets is assumed to occur outside the reaction zone in a relativistic
heavy ion collision. In contrast, a quantum mechanical estimate yields a time
on the order of only a few fm/c for building up the hadronic wavefunction for
jets with typical transverse momenta of pT < 10 GeV as accessible at RHIC
facilities. The role of possible elastic or inelastic collisions of these high
pT particles with the bulk of hadrons inside the fireball is addressed by means
of an opacity expansion in the number of collisions. This analysis shows that
the hadronic final state interactions can in principle account for the
modification of the (moderate) high pT spectrum observed for central collisions
at RHIC.Comment: 9 pages, 9 figures, standard revtex, final published versio
Charm Quark Energy Loss in QCD Matter
The energy loss of heavy quarks in a quark-gluon plasma of finite size is
studied within the light-cone integral approach. A simple analytical
formulation of the radiative energy loss of heavy quarks is derived. This
provides a convenient way to quantitatively estimate the quark energy loss. Our
results show that if the energy of a heavy quark is much larger than its mass,
the radiative energy loss approaches the radiative energy loss of light quarks.Comment: 4 pages, 2 figures. Accepted for publication in European Physical
Journal
Hadron Spectra and QGP Hadronization in Au+Au Collisions at RHIC
The transverse mass spectra of Omega hyperons and phi mesons measured
recently by STAR Collaboration in Au+Au collisions at sqrt(s_NN) = 130 GeV are
described within a hydrodynamic model of the quark gluon plasma expansion and
hadronization. The flow parameters at the plasma hadronization extracted by
fitting these data are used to predict the transverse mass spectra of J/psi and
psi' mesons.Comment: 4 pages, 4 figures, Fig. 3 correcte
Hadron Production at Intermediate at RHIC
Large proton and antiproton enhancement with respect to pions has been
observed at intermediate transverse momentum 2-5 GeV/ in Au+Au
collisions at RHIC. To investigate the possible source of this anomaly, the
production of mesons and two particle angular correlations triggered by
mid- baryons or mesons are studied. We also present the first measurement
of proton and antiproton production at GeV in Au+Au
collisions, which aims to study the energy dependence of the observed baryon
enhancement.Comment: 7 pages, 5 figures, proceedings of Hot Quarks 2004 workshop, Taos
Valley, New Mexico, 18-24 Jul 2004,, to be published in J. Phys.
- …