3,085 research outputs found
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.
Hadronization in heavy ion collisions: recombination or fragmentation?
We show that hadron production in relativistic heavy ion collisions at
transverse momenta larger than 2 GeV/c can be explained by the competition of
two different hadronization mechanisms. Above 5 GeV/c hadron production can be
described by fragmentation of partons that are created perturbatively. Below 5
GeV/c recombination of partons from the dense and hot fireball dominates. This
can explain some of the surprising features of RHIC data like the constant
baryon-to-meson ratio of about one and the small nuclear suppression for
baryons between 2 to 4 GeV/c.Comment: Contribution to the 7th Conference on Strange Quark Matter (SQM
2003), submitted to J.Phys.G; 6 pages LaTeX, 4 eps figures, uses iopart.cl
Hadron production in heavy ion collisions: Fragmentation and recombination from a dense parton phase
We discuss hadron production in heavy ion collisions at RHIC. We argue that
hadrons at transverse momenta P_T < 5 GeV are formed by recombination of
partons from the dense parton phase created in central collisions at RHIC. We
provide a theoretical description of the recombination process for P_T > 2 GeV.
Below P_T = 2 GeV our results smoothly match a purely statistical description.
At high transverse momentum hadron production is well described in the language
of perturbative QCD by the fragmentation of partons. We give numerical results
for a variety of hadron spectra, ratios and nuclear suppression factors. We
also discuss the anisotropic flow v_2 and give results based on a flow in the
parton phase. Our results are consistent with the existence of a parton phase
at RHIC hadronizing at a temperature of 175 MeV and a radial flow velocity of
0.55c.Comment: 25 pages LaTeX, 18 figures; v2: some references updated; v3: some
typos fixe
Developing a High Resolution ZDC for the EIC
The Electron Ion Collider offers the opportunity to make un-paralleled multidimen- sional measurements of the spin structure of the proton and nuclei, as well as a study of the onset of partonic saturation at small Bjorken-x [1]. An important requirement of the physics program is the tagging of spectator neutrons and the identification of forward photons. We propose to design and build a Zero Degree Calorimeter, or ZDC, to measure photons and neutrons with excellent energy & position resolution
phi meson production in Au + Au collisions at sqrt{s_{NN} = 200 GeV
We present the results on the mid-rapidity phi meson production in the
K^{+}K^{-} decay channel in Au + Au collisions at sqrt(s_NN) = 200 GeV measured
by the PHENIX experiment at RHIC. The spectral shape of the phi resonance,
studied at different collision centralities, is consistent with the particle
data book. The transverse mass spectra are measured in four centrality bins.
The inverse slopes (T), yields (dN/dy) and particle ratios are studied as a
function of centrality. The nuclear modification factor is measured through the
ratio, R_{CP}, of central to peripheral yields normalized to the number of
nucleon-nucleon collisions. The R_{CP} of the phi mesons is less than unity and
is comparable to that of pions rather than R_{CP} ~ 1 observed for protons and
anti-protons
Systematics of Inclusive Photon Production in 158 AGeV Pb Induced Reactions on Ni, Nb, and Pb Targets
The multiplicity of inclusive photons has been measured on an event-by-event
basis for 158 AGeV Pb induced reactions on Ni, Nb, and Pb targets. The
systematics of the pseudorapidity densities at midrapidity (rho_max) and the
width of the pseudorapidity distributions have been studied for varying
centralities for these collisions. A power law fit to the photon yield as a
function of the number of participating nucleons gives a value of 1.13+-0.03
for the exponent. The mean transverse momentum, , of photons determined
from the ratio of the measured electromagnetic transverse energy and photon
multiplicity, remains almost constant with increasing rho_max. Results are
compared with model predictions.Comment: 16 pages including 4 figure
Centrality Dependence of Neutral Pion Production in 158 A GeV Pb + Pb Collisions
The production of neutral pions in 158AGeV Pb+Pb collisions has been studied
in the WA98 experiment at the CERN SPS. Transverse momentum spectra are studied
for the range 0.3 GeV/c < mT-m0 < 4.0 GeV/c. The results for central collisions
are compared to various models. The centrality dependence of the neutral pion
spectral shape and yield is investigated. An invariance of the spectral shape
and a simple scaling of the yield with the number of participating nucleons is
observed for centralities with greater than about 30 participating nucleons
which is most naturally explained by assuming an equilibrated system.Comment: 5 pages, Latex, including 3 eps figures, submitted to Phys.Rev.Lett;
updated pQCD comparison due to new input from the author, updated references,
corrected plotting error in figure
Scaling of Particle and Transverse Energy Production in 208Pb+208Pb collisions at 158 A GeV
Transverse energy, charged particle pseudorapidity distributions and photon
transverse momentum spectra have been studied as a function of the number of
participants (N_{part}) and the number of binary nucleon-nucleon collisions
(N_{coll}) in 158 A GeV Pb+Pb collisions over a wide impact parameter range. A
scaling of the transverse energy pseudorapidity density at midrapidity as
N_{part}^{1.08 \pm 0.06} and N_{coll}^{0.83 \pm 0.05} is observed. For the
charged particle pseudorapidity density at midrapidity we find a scaling as
N_{part}^{1.07 \pm 0.04} and N_{coll}^{0.82 \pm 0.03}. This faster than linear
scaling with N_{part} indicates a violation of the naive Wounded Nucleon Model.Comment: 13 pages, 16 figures, submitted to European Physical Journal C
(revised results for scaling exponents
Recommended from our members
Multiparticle azimuthal correlations for extracting event-by-event elliptic and triangular flow in Au + Au collisions at sNN =200 GeV
We present measurements of elliptic and triangular azimuthal anisotropy of charged particles detected at forward rapidity 1<|η|<3 in Au + Au collisions at sNN=200 GeV, as a function of centrality. The multiparticle cumulant technique is used to obtain the elliptic flow coefficients v2{2},v2{4},v2{6}, and v2{8}, and triangular flow coefficients v3{2} and v3{4}. Using the small-variance limit, we estimate the mean and variance of the event-by-event v2 distribution from v2{2} and v2{4}. In a complementary analysis, we also use a folding procedure to study the distributions of v2 and v3 directly, extracting both the mean and variance. Implications for initial geometrical fluctuations and their translation into the final-state momentum distributions are discussed
Au+Au Reactions at the AGS: Experiments E866 and E917
Particle production and correlation functions from Au+Au reactions have been
measured as a function of both beam energy (2-10.7AGeV) and impact parameter.
These results are used to probe the dynamics of heavy-ion reactions, confront
hadronic models over a wide range of conditions and to search for the onset of
new phenomena.Comment: 12 pages, 14 figures, Talk presented at Quark Matter '9
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