21 research outputs found
Cronin Effect at Different Rapidities at RHIC
Calculations of the nuclear modification factor, R_dAu, for pi^0 production
in dAu collisions at s_NN^1/2 = 200 GeV are presented. The applied
pQCD-improved parton model incorporates intrinsic k_T. Nuclear multiscattering
and nuclear shadowing are considered in the Au nucleus. Theoretical results are
displayed for midrapidity and high pseudorapidity (eta), and compared to
preliminary PHENIX and BRAHMS data.Comment: Contributed to 17th International Conference on Ultra Relativistic
Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland, California, 11-17
Jan 200
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
PHENIX Highlights
Recent highlights of measurements by the PHENIX experiment at RHIC are
presented.Comment: 8 pages, 9 figures. Talk at Quark Matter 200
Centrality dependence of charged hadron production in deuteron+gold and nucleon+gold collisions at sqrt(s_NN)=200 GeV
We present transverse momentum (p_T) spectra of charged hadrons measured in
deuteron-gold and nucleon-gold collisions at \sqrts = 200 GeV for four
centrality classes. Nucleon-gold collisions were selected by tagging events in
which a spectator nucleon was observed in one of two forward rapidity
detectors. The spectra and yields were investigated as a function of the number
of binary nucleon-nucleon collisions, \nu, suffered by deuteron nucleons. A
comparison of charged particle yields to those in p+p collisions show that the
yield per nucleon-nucleon collision saturates with \nu for high momentum
particles. We also present the charged hadron to neutral pion ratios as a
function of p_T.Comment: 330 authors, 15 pages text, 16 figures, 3 tables. Submitted to Phys.
Rev. Lett. v2 has minor changes to reflect revisions during review process.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
High-pT pi^zero Production with Respect to the Reaction Plane in Au + Au Collisions at sqrt(s_NN) = 200 GeV
Measurements of the azimuthal anisotropy of high-\pT neutral pion neutral
pion production in Au+Au collisions at sqrt(s_NN) = 200 GeV by the PHENIX
experiment are presented. The data included in this paper were collected during
the 2004 RHIC running period and represent approximately an order of magnitude
increase in the number of analyzed events relative to previously published
results. Azimuthal angle distributions of pi^0s detected in the PHENIX
electromagnetic calorimeters are measured relative to the reaction plane
determined event-by-event using the forward and backward beam-beam counters.
Amplitudes of the second Fourier component (v_2) of the angular distributions
are presented as a function of pi^0 transverse momentum p_T for different bins
in collision centrality. Measured reaction plane dependent pi^0 yields are used
to determine the azimuthal dependence of the pi^0 suppression as a function of
p_T, R_AA (Delta phi,p_T). A jet-quenching motivated geometric analysis is
presented that attempts to simultaneously describe the centrality dependence
and reaction plane angle dependence of the pi^0 suppression in terms of the
path lengths of hypothetical parent partons in the medium. This set of results
allows for a detailed examination of the influence of geometry in the collision
region, and of the interplay between collective flow and jet-quenching effects
along the azimuthal axis.Comment: 344 authors, 35 pages text, RevTeX-4, 24 figures, 8 tables. Submitted
to Physical Review
Cold Nuclear Matter Effects on J/Psi as Constrained by Deuteron-Gold Measurements at sqrt(s_NN) = 200 GeV
We present a new analysis of J/psi production yields in deuteron-gold
collisions at sqrt(s_NN) = 200 GeV using data taken by the PHENIX experiment in
2003 and previously published in [S.S. Adler et al., Phys. Rev. Lett 96, 012304
(2006)]. The high statistics proton-proton J/psi data taken in 2005 is used to
improve the baseline measurement and thus construct updated cold nuclear matter
modification factors R_dAu. A suppression of J/psi in cold nuclear matter is
observed as one goes forward in rapidity (in the deuteron-going direction),
corresponding to a region more sensitive to initial state low-x gluons in the
gold nucleus. The measured nuclear modification factors are compared to
theoretical calculations of nuclear shadowing to which a J/psi (or precursor)
break-up cross-section is added. Breakup cross sections of sigma_breakup =
2.8^[+1.7_-1.4] (2.2^[+1.6_-1.5]) mb are obtained by fitting these calculations
to the data using two different models of nuclear shadowing. These breakup
cross section values are consistent within large uncertainties with the 4.2 +/-
0.5 mb determined at lower collision energies. Projecting this range of cold
nuclear matter effects to copper-copper and gold-gold collisions reveals that
the current constraints are not sufficient to firmly quantify the additional
hot nuclear matter effect.Comment: 453 authors from 59 institutions, 15 pages, 13 figures, 5 tables.
Submitted to Physical Review C. Plain text data tables for the points plotted
in figures for this and previous PHENIX publications are (or will be)
publicly available at http://www.phenix.bnl.gov/papers.htm
Production of phi mesons at mid-rapidity in sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC
We present the first results of meson production in the K^+K^- decay channel
from Au+Au collisions at sqrt(s_NN) = 200 GeV as measured at mid-rapidity by
the PHENIX detector at RHIC. Precision resonance centroid and width values are
extracted as a function of collision centrality. No significant variation from
the PDG accepted values is observed. The transverse mass spectra are fitted
with a linear exponential function for which the derived inverse slope
parameter is seen to be constant as a function of centrality. These data are
also fitted by a hydrodynamic model with the result that the freeze-out
temperature and the expansion velocity values are consistent with the values
previously derived from fitting single hadron inclusive data. As a function of
transverse momentum the collisions scaled peripheral.to.central yield ratio RCP
for the is comparable to that of pions rather than that of protons. This result
lends support to theoretical models which distinguish between baryons and
mesons instead of particle mass for explaining the anomalous proton yield.Comment: 326 authors, 24 pages text, 23 figures, 6 tables, RevTeX 4. To be
submitted to Physical Review C as a regular article. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
Systematic Studies of Elliptic Flow Measurements in Au+Au Collisions at sqrt(s_NN) = 200 GeV
We present inclusive charged hadron elliptic flow v_2 measured over the
pseudorapidity range |\eta| < 0.35 in Au+Au collisions at sqrt(s_NN) = 200 GeV.
Results for v_2 are presented over a broad range of transverse momentum (p_T =
0.2-8.0 GeV/c) and centrality (0-60%). In order to study non-flow effects that
are not correlated with the reaction plane, as well as the fluctuations of v_2,
we compare two different analysis methods: (1) event plane method from two
independent sub-detectors at forward (|\eta| = 3.1-3.9) and beam (|\eta| > 6.5)
pseudorapidities and (2) two-particle cumulant method extracted using
correlations between particles detected at midrapidity. The two event-plane
results are consistent within systematic uncertainties over the measured p_T
and in centrality 0-40%. There is at most 20% difference of the v_2 between the
two event plane methods in peripheral (40-60%) collisions. The comparisons
between the two-particle cumulant results and the standard event plane
measurements are discussed.Comment: 347 authors, 27 pages text, RevTeX-4, 24 figures, 10 tables.
Submitted to Physical Review
Measurement of Single Electron Event Anisotropy in Au+Au Collisions at sqrt(s_NN) = 200 GeV
The transverse momentum dependence of the azimuthal anisotropy parameter v_2,
the second harmonic of the azimuthal distribution, for electrons at
mid-rapidity (|eta| < 0.35) has been measured with the PHENIX detector in Au+Au
collisions at sqrt(s_NN) = 200 GeV. The measurement was made with respect to
the reaction plane defined at high rapidities (|eta| = 3.1 -- 3.9). From the
result we have measured the v_2 of electrons from heavy flavor decay after
subtraction of the v_2 of electrons from other sources such as photon
conversions and Dalitz decay from light neutral mesons. We observe a non-zero
single electron v_2 with a 90% confidence level in the intermediate p_T region.Comment: 330 authors, 11 pages text, RevTeX4, 9 figures, 1 tables. Submitted
to Physical Review C. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (or will be) publicly
available at http://www.phenix.bnl.gov/papers.htm
Systematic Studies of the Centrality and sqrt(s_NN) Dependence of dE_T/deta and dN_ch/deta 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 sqrt(s_NN) = 19.6,
130 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 sqrt(s_NN) dependence of dE_T/deta and dN_ch/deta per pair of participants
is consistent with logarithmic scaling for the most central events. The
centrality dependence of dE_T/deta and dN_ch/deta 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
sqrt(s_NN). A survey of comparisons between the data and available theoretical
models is also presented.Comment: 327 authors, 25 pages text, 19 figures, 17 tables, RevTeX 4. To be
submitted to Physical Review C as a regular article. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm