11 research outputs found
CGC, QCD Saturation and RHIC data (Kharzeev-Levin-McLerran-Nardi point of view)
This is the talk given at the Workshop:"Focus on Multiplicitioes", Bari,
Italy, 17-19 June,2004.. In this talk, we are going to discuss ion-ion and
deuteron - nucleus RHIC data and show that they support, if not more, the idea
of the new QCD phase: colour glass condensate with saturated parton density. .Comment: 26 pages with 33 figure
Centrality and dE_{T}/d\etadN_{ch}/d\eta$ in Heavy Ion Collisions at Mid-Rapidity
The PHENIX experiment at RHIC has measured transverse energy and charged
particle multiplicity at mid-rapidity in Au + Au collisions at
= 19.6, 130, 62.4 and 200 GeV as a function of centrality. The presented
results are compared to measurements from other RHIC experiments, and
experiments at lower energies. The dependence of
and per pair of participants is consistent with logarithmic
scaling for the most central events. The centrality dependence of
and is similar at all measured incident
energies. At RHIC energies the ratio of transverse energy per charged particle
was found independent of centrality and growing slowly with . A
survey of comparisons between the data and available theoretical models is also
presented.Comment: Proccedings of the Workshop: Focus on Multiplcity at Bari, Italy,
June 17-19,2004. To be submitted to the Jornal of Physics, "Conference
series". Includes: 20 Pages, 15 figures, 3 Tables, 80 Referencie
High pT hadron spectra at RHIC: an overview
Recent results on high transverse momentum (pT) hadron production in p+p,
d+Au and Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) are
reviewed. Comparison of the nuclear modification factors, and
, demonstrates that the large suppression in central Au+Au
collisions is due to strong final-state effects. Theoretical models which
incorporate jet quenching via gluon Bremsstrahlung in the dense partonic medium
that is expected in central Au+Au collisions at ultra-relativistic energies are
shown to reproduce the shape and magnitude of the observed suppression over the
range of collision energies so far studied at RHIC.Comment: 12 pages, 10 figures, Talk given at Hot Quarks 2004: Workshop for
Young Scientists on the Physics of Ultrarelativistic Nucleus-Nucleus
Collisions (HQ'04), Taos Valley, New Mexico, 18-24 Jul 2004, to be published
in J. Phys.
System size, energy, centrality and pseudorapidity dependence of charged-particle density in Au+Au and Cu+Cu collisions at RHIC
Charged particle pseudorapidity distributions are presented from the PHOBOS
experiment at RHIC, measured in Au+Au and Cu+Cu collisions at sqrt{s_NN}=19.6,
22.4, 62.4, 130 and 200 GeV, as a function of collision centrality. The
presentation includes the recently analyzed Cu+Cu data at 22.4 GeV. The
measurements were made by the same detector setup over a broad range in
pseudorapidity, |eta|<5.4, allowing for a reliable systematic study of particle
production as a function of energy, centrality and system size. Comparing Cu+Cu
and Au+Au results, we find that the total number of produced charged particles
and the overall shape (height and width) of the pseudorapidity distributions
are determined by the number of nucleon participants, N_part. Detailed
comparisons reveal that the matching of the shape of the Cu+Cu and Au+Au
pseudorapidity distributions over the full range of eta is better for the same
N_part/2A value than for the same N_part value, where A denotes the mass
number. In other words, it is the geometry of the nuclear overlap zone, rather
than just the number of nucleon participants that drives the detailed shape of
the pseudorapidity distribution and its centrality dependence.Comment: 5 pages, 4 figures. Presented at the 20th International Conference on
Nucleus-Nucleus Collisions (Quark Matter 2008), Jaipur, Rajasthan, India,
4-10 February 200
Rapidity and k_T dependence of HBT correlations in Au+Au collisions at 200 GeV with PHOBOS
Two-particle correlations of identical charged pion pairs from Au+Au
collisions at sqrt(s_NN) = 200 GeV were measured by the PHOBOS experiment at
RHIC. Data for the most central (0--15%) events were analyzed with
Bertsch-Pratt (BP) and Yano-Koonin-Podgoretskii (YKP) parameterizations using
pairs with rapidities of 0.4 < y < 1.3 and transverse momenta 0.1 < k_T < 1.4
GeV/c. The Bertsch-Pratt radii decrease as a function of pair transverse
momentum. The pair rapidity Y_pipi roughly scales with the source rapidity
Y_YKP, indicating strong dynamical correlations.Comment: 5 pages, 2 figures. To appear in the proceedings of Seventeenth
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter 2004), Oakland, California from January 11-17, 2004. Submitted
to Journal of Physics G: Nuclear and Particle Physic
Pseudorapidity Distributions of Charged Particles in d + Au and p + p Collisions at = 200GeV
The measured pseudorapidity distributions of primary charged particles are
presented for d + Au and p + p collisions at 200 GeV
over a wide pseudorapidity range of 5.4. The results
for d + Au collisions are presented for minimum-bias events and as a function
of collision centrality. The measurements for p + p collisions are shown for
minimum-bias events. The ratio of the charged particle multiplicity in d + Au
and p + A collisions relative to that for inelastic p + p collisions is found
to depend only on , and it is remarkably independent of
collision energy and system mass. The deuteron and gold fragmentation regions
in d + Au collisions are in good agreement with proton nucleus data at lower
energies.Comment: 4 pages, 3 figures. To appear in the proceedings of Seventeenth
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter 2004), Oakland, California from January 11-17, 2004. Submitted
to Journal of Physics G: Nuclear and Particle Physic
The Landscape of Particle Production: Results from PHOBOS
Recent results from the PHOBOS experiment at RHIC are presented, both from
Au+Au collisions from the 2001 run and p+p and d+Au collisions from 2003. The
centrality dependence of the total charged particle multiplicity in p+p and
d+Au show features, such as Npart-scaling and limiting fragmentation, similar
to p+A collisions at lower energies. Multiparticle physics in Au+Au is found to
be local in (pseudo)rapidity, both when observed by HBT correlations and by
forward-backward pseudorapidity correlations. The shape of elliptic flow in
Au+Au, measured over the full range of pseudorapidity, appears to have a very
weak centrality dependence. Identified particle ratios in d+Au reactions show
little difference between the shape of proton and anti-proton spectra, while
the absolute yields show an approximate m_T scaling.Comment: 8 Pages, 11 Figures, Plenary talk at Quark Matter 2004, Oakland, CA,
January 11-18, 200
Scaling properties in bulk and p-dependent particle production near midrapidity in relativistic heavy ion collisions
The centrality dependence of the midrapidity charged-particle multiplicity
density (1) is presented for Au+Au and Cu+Cu collisions at RHIC over
a broad range of collision energies. The multiplicity measured in the Cu+Cu
system is found to be similar to that measured in the Au+Au system, for an
equivalent N, with the observed factorization in energy and
centrality still persistent in the smaller Cu+Cu system. The extent of the
similarities observed for bulk particle production is tested by a comparative
analysis of the inclusive transverse momentum distributions for Au+Au and Cu+Cu
collisions near midrapidity. It is found that, within the uncertainties of the
data, the ratio of yields between the various energies for both Au+Au and Cu+Cu
systems are similar and constant with centrality, both in the bulk yields as
well as a function of p, up to at least 4 GeV/. The effects of
multiple nucleon collisions that strongly increase with centrality and energy
appear to only play a minor role in bulk and intermediate transverse momentum
particle production.Comment: Submitted for publication in Phys. Rev. C, 5 pages, 3 figure
Recommended from our members
GLOBAL OBSERVATIONS FROM PHOBOS.
Particle production in Au+Au collisions has been measured in the PHOBOS experiment at RHIC for a range of collision energies. Three empirical observations have emerged from this dataset which require theoretical examination. First, there is clear evidence of limiting fragmentation. Namely, particle production in central Au + Au collisions, when expressed as dN/d{eta}{prime} ({eta}{prime} {triple_bond} {eta} - y{sub beam}), becomes energy independent at high energy for a broad region of {eta}{prime} around {eta}{prime} = 0. This energy-independent region grows with energy, allowing only a limited region (if any) of longitudinal boost-invariance. Second, there is a striking similarity between particle production in e{sup +}e{sup -} and Au + Au collisions (scaled by the number of participating nucleon pairs). Both the total number of produced particles and the longitudinal distribution of produced particles are approximately the same in e{sup +}e{sup -} and in scaled Au + Au. This observation was not predicted and has not been explained. Finally, particle production has been found to scale approximately with the number of participating nucleon pairs for <N{sub part}> > 65. This scaling occurs both for the total multiplicity and for high p{sub T} particles (3 < p{sub T} < 4.5 GeV/c)
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First results from the PHOBOS experiment at RHIC.
The PHOBOS experiment at RHIC has measured the charged-particle density dN/d{eta} at mid-rapidity for central Au+Au collisions at center of mass energies of {radical}s{sub NN} = 56, and 130 GeV. We deduce that dN/d{eta} = 408 {+-} 12(stat) {+-}30(syst) and 555 {+-} 12(stat) {+-} 35(syst) for collision energies of 56, and 130, GeV, respectively. These numbers suggest energy densities that are some 70% higher than have been achieved in any heavy-ion collisions previously studied, and also 25-40% higher than nucleon-nucleon collisions at comparable center of mass energies