共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Putschke 《The European Physical Journal C - Particles and Fields》2007,49(1):57-59
Systematic measurements of pseudorapidity (Δη) and azimuthal (Δϕ) correlations between high-pt charged hadrons and associated particles from the high statistics 200 GeV Au+Au and Cu+Cu datasets will be presented. In
previous measurements differences in the near-side Δη correlation between central Au+Au and the lighter systems, d+Au and
p+p, were observed, including a long-range near-side correlation in Au+Au collisions. Studies to characterize the properties
of the long-range correlation will be presented.
PACS 25.75.Dw; 25.75.Gz 相似文献
2.
M. Naglis 《The European Physical Journal C - Particles and Fields》2009,61(4):835-840
The PHENIX experiment at RHIC has measured a variety of light neutral mesons (π
0, K
S
0, η, ω, η
′, φ) via multi-particle decay channels over a wide range of transverse momentum. A review of the recent results on the production
rates of light mesons in p + p and their nuclear modification factors in d + Au, Cu + Cu and Au + Au collisions at different
energies is presented. 相似文献
3.
G. L. Ma S. Zhang Y. G. Ma X. Z. Cai J. H. Chen C. Zhong 《The European Physical Journal C - Particles and Fields》2008,57(3):589-593
Longitudinal broadening along the Δη direction on the near side in the two-dimensional (Δφ×Δη) di-hadron correlation distribution has been studied for central Au+Au collisions at
GeV, within a dynamical multi-phase transport model. It was found that longitudinal broadening is generated by a longitudinal
flow induced by a strong parton cascade in central Au+Au collisions, to be compared with p+p collisions at
GeV. The longitudinal broadening may shed light on the strongly interacting partonic matter at RHIC. 相似文献
4.
J. Bielcikova 《The European Physical Journal C - Particles and Fields》2007,49(1):321-326
We present results on two-particle azimuthal correlations of neutral strange baryons (Λ, Λ̄) and mesons (KS
0) for pT=2–6 GeV/c associated with non-identified charged particles in d+Au and Au+Au collisions at =200 GeV measured by the STAR experiment. We investigate in detail the associated yield of charged particles as a function
centrality of the collision and transverse momentum of trigger and associated particles to look for possible flavor, baryon/meson
and particle/anti-particle differences. We compare our results to the proton and pion triggered correlations as well as to
a fragmentation and recombination model.
PACS 25.75.-q; 25.75.Gz 相似文献
5.
S. Sakai 《The European Physical Journal C - Particles and Fields》2007,49(1):383-387
The PHENIX experiment has measured the azimuthal anisotropy parameter v2, the second harmonic of the azimuthal distribution, for electrons at mid-rapidity (|η|<0.35) as a function of transverse
momentum (0.5<pT (GeV/c)<5.0) in Au+Au collisions at =200 GeV. From the result we have calculated the non-photonic electron v2, which is expected to reflect charm quark azimuthal anisotropy, by subtracting the v2 of electrons from other sources such as photon conversions and Dalitz decays. 相似文献
6.
L. Gaillard 《The European Physical Journal C - Particles and Fields》2007,49(1):51-55
Here we present initial studies of two-dimensional angular correlations of Λ, Λ̄, and K0
Short triggers with unidentified charged hadrons in Au+Au collisions at =200 GeV measured by STAR. Distributions of pseudo-rapidity difference, Δη, and azimuthal separation, Δφ, are constructed
containing structures observed in unidentified hadron correlations, including a jet peak at small Δη-Δφ accompanied by a flow-like
ridge extended over Δη. These features are studied as a function of centrality via integrated yields and fitting to projections
onto Δη and Δφ axes. Yields are found to be consistent with unidentified correlation analyses, and no clear distinction is
observed between the three species.
PACS 25.75.Gz 相似文献
7.
Hiroshi Masui 《The European Physical Journal C - Particles and Fields》2009,62(1):169-173
One of the most striking results is the large elliptic flow (v
2) at RHIC. Detailed mass and transverse momentum dependence of elliptic flow are well described by ideal hydrodynamic calculations
for p
T<1 GeV/c, and by parton coalescence/recombination picture for p
T=2–6 GeV/c. The systematic error on v
2 is dominated by so-called “non-flow effects”, which are correlations other than flow, such as resonance decays and jets.
It is crucial to understand and reduce the systematic error from non-flow effects in order to understand the underlying collision
dynamics. In this paper, we present the centrality dependence of v
2 with respect to the first harmonic event plane at ZDC-SMD (v
2{ZDC-SMD}) in Au + Au collisions at
GeV. A large rapidity gap (|Δη|>6) between midrapidity and the ZDC-SMD could enable us to minimize possible non-flow contributions. We compare the results
of v
2{ZDC-SMD} with v
2{BBC}, which is measured by event plane determined at |η|=3.1–3.9. Possible non-flow contributions in those results will be discussed. 相似文献
8.
P. Romatschke 《The European Physical Journal C - Particles and Fields》2007,52(1):203-209
Causal viscous hydrodynamic fits to experimental data for pion and kaon transverse momentum spectra from central Au + Au collisions
at are presented. Starting the hydrodynamic evolution at 1 fm/c and using small values for the relaxation time, reasonable fits up to moderate ratios, η/s≃0.4, can be obtained. It is found
that a percentage of roughly 50 η/s to 75 η/s of the final meson multiplicity is due to viscous entropy production. Finally,
it is shown that with increasing viscosity, the ratio of HBT radii Rout/Rside approaches and eventually matches the experimental data. 相似文献
9.
Anthony R. Timmins 《The European Physical Journal C - Particles and Fields》2009,62(1):249-254
We report STAR measurements of mid-rapidity yields for the Λ ,
, K
S
0 , Ξ
−,
, Ω
−,
particles in Cu + Cu and Au + Au
GeV collisions. We show that at a given number of participating nucleons, bulk strangeness production is higher in Cu + Cu
collisions compared to Au + Au collisions at the same center of mass energy, counter to predictions from the Canonical formalism.
We compare both the Cu + Cu and Au + Au yields to AMPT and EPOS predictions, and find they reproduce key qualitative aspects
of the data. Finally, we investigate other scaling parameters and find bulk strangeness production for both the measured data
and theoretical predictions, scales better with the number participants that undergo more than one collision. 相似文献
10.
M. V. Tokarev 《Physics of Atomic Nuclei》2011,74(5):799-804
The production of hadrons in heavy-ion collisions at high-p
T
provides an important information on mechanism of particle formation and constituent energy loss in medium. Such information
is needed for search of a Critical Point and signatures of phase transition. Measurements by the STAR Collaboration of charged
hadron production in Au + Au collisions at √s
NN
= 9.2 GeV over a wide transverse momentum p
T
= 0.2−4 GeV/c and at mid-rapidity range are reported. It allows for a first measurement of the spectra for charged hadrons at high p
T
at this energy. The spectra demonstrate the dependence on centrality which enhances with p
T
. The constituent energy loss and its dependence on transverse momentum of particle, and centrality of collisions are estimated
in the z-scaling approach. 相似文献
11.
The energy excitation functions of directed flow (v1) and elliptic flow (v2) from Ebeam=90 A MeV to Ecm=200 A GeV are explored within the UrQMD framework and discussed in the context of the available data. The radial and the elliptic
flow of the particles produced in a relativistic heavy-ion collision are intimately connected to the pressure and its gradients
in the early stage of the reaction. Therefore, these observables should also be sensitive to changes in the equation of state.
To prove this connection, the temporal evolution of the pressure, pressure gradients and elliptic flow are shown. For the
flow excitation functions it is found that, in the energy regime below Ebeam≤10 A GeV, the inclusion of nuclear potentials is necessary to describe the data. Above 40 A GeV beam energy, the UrQMD model starts to underestimate the elliptic flow. Around the same energy the slope of the rapidity
spectra of the proton directed flow develops negative values. This effect is known as the third flow component (“antiflow”)
and cannot be reproduced by the transport model. The difference between the data and the UrQMD model can possibly be explained
by assuming a phase transition from hadron gas to quark–gluon plasma around Elab=40 A GeV. This would be consistent with the model calculations, indicating a transition from hadronic matter to “string matter”
in this energy range. Thus, we speculate that the missing pressure might be generated by strong interactions in the early
pre-hadronic/partonic phase of central Au + Au (Pb + Pb) collisions already at lower SPS energies.
PACS 25.75.-q; 25.75.Ld; 25.75.Dw; 25.75.Gz; 24.10.Lx 相似文献
12.
M. van Leeuwen 《The European Physical Journal C - Particles and Fields》2009,61(4):569-574
We present selected recent results of multi-hadron correlation measurements in azimuth and pseudorapidity at intermediate
and high p
T
in Au+Au collisions at
, from the STAR experiment at RHIC. At intermediate p
T
, measurements are presented that attempt to determine the origin of the associated near-side (small Δφ) yield at large pseudo-rapidity difference Δη that is found to be present in heavy ion collisions. In addition, results are reported on new multi-hadron correlation measures
at high-p
T
that use di-hadron triggers and multi-hadron cluster triggers with the goal to constrain the underlying jet kinematics better
than in the existing measurements of inclusive spectra and di-hadron correlations. 相似文献
13.
Y. Hama R. P. G. Andrade F. Grassi W. -L. Qian T. Osada C. E. Aguiar T. Kodama 《Physics of Atomic Nuclei》2008,71(9):1558-1564
By using the NeXSPheRIO code, we study the elliptic-flow fluctuations in Au + Au collisions at 200 A GeV. It is shown that, by fixing the parameters of the model to correctly reproduce the charged pseudorapidity and the transverse-momentum
distributions, reasonable agreement of 〈v
2〉 with data is obtained, both as function of pseudorapidity as well as of transverse momentum, for charged particles. Our
results on elliptic-flow fluctuations are in good agreement with the recently measured data on experiments.
The text was submitted by the authors in English. 相似文献
14.
Jiangyong Jia 《Indian Journal of Physics》2011,85(1):149-154
We provide a detailed survey study of dihadron azimuthal angle (Δϕ) correlations in a broad range of transverse momentum (0.4 < p
T
< 10 GeV/c) and centrality (0–92%) in Au+Au collisions at 149-2 = 200 GeV. The evolution of the jet shape and yield with p
T
seems to suggest two distinct components at the away-side pairs: a suppressed jet fragmentation component around Δϕ ∼ π, and a medium-induced components around |Δϕ − π| ∼ 1.1. The former dominates p
T
> 5 GeV/c and the later dominates at p
T
< 4 GeV/c. 相似文献
15.
S. Shi 《Indian Journal of Physics》2011,85(7):1137-1141
Elliptic flow allows us to probe early dynamics in high energy nuclear collisions. The υ
2 result of charged hadrons and identified hadrons [1,2] from 200 GeV Au+Au collisions at RHIC suggest that the matter with
partonic collectivity and thermalization has been formed in central collisions. In this analysis, we present preliminary results
of υ
2 for K
S
0 and Λ from 200 GeV Cu+Cu collisions. The partonic collectivity and thermalization assumption are tested in smaller Cu+Cu system
comparing with those from Au+Au collisions. 相似文献
16.
《Pramana》2003,61(5):865-876
Particle production in Au+Au collisions has been measured in the PHOBOS experiment at RHIC for a range of collision energies
for a large span of pseudorapidities, |η| < 5.4. Three empirical observations have emerged from this data set which require
theoretical examination. First, there is clear evidence of limiting fragmentation. Namely, particle production in central
Au + Au collisions, when expressed as dN/dη′ ( η′ ≡ – ybeam), becomes energy independent at high energy for a broad region of η′ around η′ = 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+e−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+e−and in scaled Au + Au. This observation This presentation is based in large part on the PHOBOS summary talk by M Baker at
the16th Int. Conf. on Ultrarelativistic Nucleus- Nucleus Collisions, Quark Matter 2002, Nantes, France 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
part
) > 65. This scaling occurs both for the total multiplicity and for highp
T
particles (3 <p
T
< 4.5 GeV/c).
This presentation is based in large part on the PHOBOS summary talk by M Baker at the16th Int. Conf. on Ultrarelativistic Nucleus-Nucleus Collisions, Quark Matter 2002, Nantes, France 相似文献
17.
F. Benedosso 《The European Physical Journal C - Particles and Fields》2007,49(1):61-64
We present measurements of azimuthal correlations between photons (from π0 decay) and charged hadrons in d+Au collisions at =200 GeV. We use di-hadron correlations to study parton fragmentation in d+Au collisions at RHIC. Specifically, the near-side
and away-side peaks of the azimuthal angular difference distribution are used to measure the root-mean-squared (RMS) fragmentation
transverse momentum and the mean intrinsic parton transverse momentum . The measurements with leading photons are compared to results using leading charged particles.
PACS 25.75.-q 相似文献
18.
B. B. Back 《Acta Physica Hungarica A》2006,25(2-4):499-506
The PHOBOS Collaboration has measured charged particles emitted over the range ?5.4<η<5.4 for Au+Au collisions at energies of $\sqrt {s_{NN} } = 19.6$ , 62.4, 130 and 200 GeV. In this contribution I will present recent results on the pseudorapidity distributions, total charged-particle production, and collective flow of particles obtained from these measurements. 相似文献
19.
J?rn?Putschke 《The European Physical Journal C - Particles and Fields》2009,61(4):629-635
Measurements of inclusive hadron suppression and di-hadron azimuthal correlations in ultra-relativistic nuclear collisions
at RHIC have provided important insights into jet quenching in hot QCD matter, but are limited in their sensitivity due to
well-known biases. Full jet reconstruction in heavy-ion collisions would conceptually provide a direct measurement of the
energy of the scattered parton before energy loss, alleviating such biases and allowing a measurement of the energy loss probability
distribution in a model-independent way from hard probes. In these proceedings we utilize recent progress in the reconstruction
of jets in the heavy ion environment and present the first measurement of the fragmentation function from fully reconstructed
jets in heavy ion collisions. The fragmentation function measured in central Au + Au collisions at
GeV will be presented and discussed with respect to p + p reference measurements. 相似文献
20.
Kh. K. Olimov 《Physics of Atomic Nuclei》2010,73(3):433-442
A procedure that relies on analyzing the angle between the momenta of the proton and the pion originating from CTa interaction
at a projectile momentum of 4.2 GeV/c per nucleon was used to investigate for the first time the production of Δ0 and Δ++ resonances in such interactions and to determine their parameters. The criterion of stability in the parameter a characterizing the background contribution was presented for the first time and was used to reconstruct the mass distributions
of Δ0 and Δ++ resonances. The contributions of Δ0- and Δ++-resonance decays to the production of charged pions were estimated. The results of this study are compared with similar data
obtained by using the analogous procedure for Δ0 and Δ++ resonances produced on carbon nuclei in CC and 4HeC collisions at a projectile momentum of 4.2 GeV/c per nucleon and in π
−12C interactions at a projectile momentum of 40 GeV/c. 相似文献