共查询到20条相似文献,搜索用时 31 毫秒
1.
L. Kumar 《Indian Journal of Physics》2011,85(6):843-847
We present the results on measurement of event-by-event p
t
fluctuations and correlations for Cu+Cu collisions at ?{sNN }\sqrt {s_{NN} } = 62.4 and 200 GeV from STAR experiment at RHIC. These results are compared with those from Au+Au collisions at ?{sNN }\sqrt {s_{NN} } = 62.4 and 200 GeV to study the system size dependence. We find that the dynamical p
t
fluctuations are finite and decrease with increasing collision centrality. The p
t
correlations are studied as a function of collision centrality and are observed to decrease as we go from peripheral to central
collisions. The square root of p
t
correlations scaled by mean p
t
are observed to be independent of beam energy as well as colliding ion size. 相似文献
2.
T. J. Tarnowsky 《Indian Journal of Physics》2011,85(7):1091-1095
Long-range forward-backward multiplicity correlations have been measured in heavy ion collisions at RHIC. Results for short
and long-range multiplicity correlations (forward-backward) are presented for several systems (Au+Au, Cu+Cu, and pp) and energies (e.g.
?{sNN }\sqrt {s_{NN} } = 200 and 62.4 GeV). A strong, long-range correlation is seen for central heavy ion collisions at ?{sNN }\sqrt {s_{NN} } = 200 GeV that vanishes in semi-peripheral events and pp collisions. There is no apparent scaling with the number of participants (N
part) involved in the collision. These correlations provide information about the longitudinal behavior of the system formed in
heavy ion collisions. To access the transverse behavior, the clusters produced in the same heavy ion collisions have been
characterized by a study of the energy and system size dependence of the percolation density parameter (ρ). The relationship between the long-range correlation and percolation has been explored to characterize the hadron-quark/gluon
phase transition and rapid thermalization of the system. 相似文献
3.
S. A. Voloshin 《Indian Journal of Physics》2011,85(7):1103-1107
In non-central relativistic heavy ion collisions, P\mathcal{P}-odd domains, which might be created in the process of the collision, are predicted to lead to charge separation along the
system orbital momentum [1]. An observable, P\mathcal{P}-even, but directly sensitive to the charge separation effect, has been proposed in Ref. [2] and is based on 3-particle mixed
harmonics azimuthal correlations. We report the STAR measurements using this observable for Au+Au and Cu+Cu collisions at
?{sNN }\sqrt {s_{NN} } = 200 and 62 GeV. The results are reported as function of collision centrality, particle separation in rapidity, and particle
transverse momentum. Effects that are not related to parity violation but might contribute to the signal are discussed. 相似文献
4.
In order to trace the initial interaction in ultra-relativistic heavy ion collision in all azimuthal directions, neighboring
angular-bin multiplicity correlation pattern is suggested. From the simulation of Au+Au collisions at ?{sNN }\sqrt {s_{NN} } = 200 GeV by using the Monte Carlo models RQMD with hadron re-scattering and AMPT with and without string melting, we observe
that the correlation pattern changes gradually from out-of-plane preferential one to inplane preferential one when the centrality
of collision shifts from central to peripheral. This regularity is found to be model and collision energy independent. The
physics behind the two opposite trends of correlation pattern is discussed. 相似文献
5.
M. Zawisza 《Indian Journal of Physics》2011,85(7):1051-1056
Correlations between non-identical particles at small relative velocity probe asymmetries in the average space-time emission
points at freezeout [1]. Such asymmetries may arise from long-lived resonances, bulk collective effects, or differences in
the freezeout scenario for the different particle species. STAR has extracted pion-proton correlation functions from a high-statistics
dataset of Au+Au collisions at ?{sNN }\sqrt {s_{NN} } = 200 GeV. We present a femtoscopic analysis of this data for all combinations of charged pions and (anti-) protons, for
collisions of different centrality. The measurements are compared with calculations of a simple Blast-wave model, in which
asymmetries are driven only by collective flow, as well as with Therminator [2], which also accounts fully for resonance effects. 相似文献
6.
Y. Ming 《Indian Journal of Physics》2011,85(6):861-865
The Time-of-Flight detector, based on MRPC technology, has greatly enhanced particle identification capability in STAR. By
combining dE/dx measured by the TPC and velocity information from the TOF, we have extended the charged kaon transverse momentum spectra
measurements up to ρ
T
− 5 GeV/c at mid-rapidity for Au+Au collisions at ?{sNN }\sqrt {s_{NN} } = 200 GeV. Estimation of charged kaon’s contribution factors from K* and ϕ is also made. 相似文献
7.
The BRAHMS measurement of proton-to-pion ratios in Au+Au and p+p collisions at $
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 62.4 GeV and $
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 200 GeV is presented as a function of transverse momentum and collision centrality within the pseudorapidity range 0 ≤
η ≤ 3. The baryo-chemical potential, μ
B
, for the indicated data spans from μ
B
≈ 26 MeV ($
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
200 GeV, η ≈ 0) to μ
B
∼ 260 MeV ($
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 62.4 GeV, η ≈ 3) [1]. The p/πratio measured for Au+Au system at $
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
62.4 GeV, η ≈ 3 reaches astounding value of 8–10 at p
T
> 1.5 GeV/c. For these energy and pseudorapidity interval no centrality dependency of p/π ratio is observed. Moreover, the baryon-to-meson ratio of nucleus-nucleus data are consistent with results obtained for p+p
interactions. 相似文献
8.
M. C. Suarez 《Indian Journal of Physics》2011,85(7):1085-1089
We present an analysis of relative baryon to meson production for intermediate transverse momentum hadrons associated with
a high-p
T
trigger. The results of pion and (anti)proton spectra and ratios are presented for the “jet” and “ridge” components of the
two-dimensional Δν − Δϕ triggered correlations in central Au+Au collisions at ?{sNN }\sqrt {s_{NN} } = 200 GeV. We compare these results with the inclusive (non-triggered) measurements for the same data, and discuss our observations
in conjunction with the results from d+Au, and pp data. 相似文献
9.
Stopping in heavy ion collisions has been measured at several energies from AGS to RHIC (spanning $
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 5 GeV to $
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 200 GeV).The systematics of stopping hint the onset of a collision regime that might include LHC energies. Stopping in
$
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 62.4 GeV Au+Au collisions contribute to the understanding of different collision systems. 相似文献
10.
Claude A. Pruneau 《Acta Physica Hungarica A》2006,25(2-4):401-408
We present measurements of dynamical net charge fluctuations in Au+Au collisions at $\sqrt {s_{NN} } = 20$ , 62, 130 and 200 GeV using the measure ν +?,dyn. We observe the dynamical fluctuations are finite at all energies, and do not exhibit dependence on beam energy. We find net charge fluctuations violate the trivial 1/N scaling expected for nuclear collisions consisting of independent nucleon-nucleon interactions. We also find dynamical fluctuations exhibit sizable dependence of the pseudo-rapidity and azimuthal ranges of integration. We compare measured data with transport models and a toy model invoking radial flow, and show the bulk of the measured correlations can be accounted for by resonance production and radial collective flow. 相似文献
11.
T. Tarnowsky 《Physics of Atomic Nuclei》2012,75(5):546-549
Results from new measurements of dynamical K/?? and p/?? ratio fluctuations are presented. Dynamical fluctuations in global conserved quantities such as baryon number, strangeness, or charge may be observed near a QCD critical point. The STAR experiment has previously acquired data in AuAu collisions at the energies $\sqrt {s_{NN} }$ = 200, 130, 62.4, and 19.6 GeV and CuCu collisions at $\sqrt {s_{NN} }$ = 200, 62.4, and 22.4 GeV. The commencing of a QCD critical point search at RHIC has extended the reach of possible measurements of dynamical K/?? and p/?? ratio fluctuations from AuAu collisions to lower energies. New results are compared to previous measurements and to theoretical predictions from the UrQMD model. 相似文献
12.
G. I. Veres 《Indian Journal of Physics》2011,85(7):1015-1019
Charged particle pseudorapidity distributions are presented from the PHOBOS experiment at RHIC, measured in Au+Au and Cu+Cu
collisions at ?{sNN }\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, |η| < 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 η 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. 相似文献
13.
R. Sahoo 《Indian Journal of Physics》2011,85(6):897-901
Transverse energy (E
T
) has been measured with both of its components, namely hadronic (E
T
had
) and electromagnetic (E
T
em
) in a common phase space at mid-rapidity for 62.4 GeV Au+Au collisions by the STAR experiment. E
T
production with centrality and ?{sNN }\sqrt {s_{NN} } is studied with similar measurements from SPS to RHIC and is compared with a final state gluon saturation model (EKRT). The
most striking feature is the observation of a nearly constant value of E
T
/N
ch
∼ 0.8 GeV from AGS, SPS to RHIC. The initial energy density estimated by the boost-invariant Bjorken hydrodynamic model,
is well above the critical density for a deconfined matter of quarks and gluons predicted by lattice QCD calculations. 相似文献
14.
The PHENIX experiment has measured, J/ψ, ψ′ and γ productions for different collision systems in the forward rapidities 1.2 < | η | < 2.2 at ?{SNN }\sqrt {S_{NN} } = 200 GeV. We have observed significant suppressions of J/ψ production in both Cu+Cu and Au+Au collisions relative to the yield in p+p system. The measurements of higher mass heavy
quarkonia states (ψ′ and γ) will help us to constrain various quarkonium suppression models in heavy ion collisions. A first hint of ψ′ and γ productions in 200GeV p+p collisions has been observed at forward and backward rapidities at PHENIX. 相似文献
15.
We present the measurement of directed flow (v
1) for the identified particles, namely, Λ, $
\bar \Lambda
$
\bar \Lambda
and K
s
0, as a function of rapidity and centrality in Au+Au collisions at $
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 200 GeV and 62.4 GeV. The measurement is based on the run IV data obtained by the STAR experiment at RHIC. In order to
enhance event plane resolution, we use tracks reconstructed from the Forward Time Projection Chambers (FTPCs), together with
the sideward deflection of spectator neutrons measured by the STAR’s Shower Maximum Detector at Zero Degree Calorimeters (ZDC-SMDs).
We find that for 200 GeV, proton and antiproton v
1 is less than 1%, the K
s
0
Λ, $
\bar \Lambda
$
\bar \Lambda
v
1 is less than 2%; for 62 GeV, proton v
1 is less than 1% and antiproton is less than 2%, v
1 for K
s
0, Λ, $
\bar \Lambda
$
\bar \Lambda
is less than 2% in Au+Au collisions at 200 GeV. 相似文献
16.
Gary D. Westfall 《Acta Physica Hungarica A》2004,21(2-4):249-254
The balance function is based on the principle that charge is locally conserved when particles are pair produced. Balance functions have been measured for all charged pairs, identified pion pairs, and identified charged kaon pairs in Au+Au collisions at $\sqrt {s_{NN} } = 200$ GeV and p+p collisions at $\sqrt {s_{NN} } = 200$ GeV at the Relativistic Heavy Ion Collider using STAR. Balance functions for all charged particles from Au+Au scale smoothly with centrality to the p+p value. Balance functions for charged particles and pions are narrower in central collisions than in peripheral collisions consistent with trends predicted by models incorporating the concept of late hadronization. Balance functions for kaon pairs represent a strangeness balance. Balance functions for kaons are narrower than those for pion pairs and may show less dependence on centrality. 相似文献
17.
Hongyan Yang for the BRAHMS Collaboration 《Czechoslovak Journal of Physics》2006,56(1):A27-A37
The main experimental results obtained by the BRAHMS experiment at Relativistic Heavy Ion Collider (RHIC) for Au+Au collisions at \(\sqrt {s_{NN} } \) =62.4, 200 GeV and d+Au collisions at \(\sqrt {s_{NN} } \) = 200GeV are presented. The m T spectra and the Gaussian-like rapidity densities of produced pions and kaons in Au+Au central collisions at \(\sqrt {s_{NN} } \) = 200 are GeV shown, and their rapidity densities are compared with results from models. The net-proton yield in the same system is compared with that from AGS and SPS energies to study the high energy collision scenario-transparency and stopping. The rapidity, energy and centrality dependence of the nuclear modification factors in both systems are compared with models to differentiate between the initial and final state effect. 相似文献
18.
A. László 《Indian Journal of Physics》2011,85(6):787-791
Transverse momentum spectra up to 4.5GeV/c were measured around midrapidity in Pb+Pb reactions at ?{sNN }\sqrt {s_{NN} } = 17.3GeV, for π
±, p, [`(p)]\bar p and K
±, by the NA49 experiment. The nuclear modification factors R
AA
, R
AA/pA
and R
CP
were extracted and are compared to RHIC results at ?{SNN }\sqrt {S_{NN} } = 200GeV. The modification factor R
AA
shows a rapid increase with transverse momentum in the covered region. The modification factor R
CP
shows saturation well below unity in the π
± channel. The extracted R
CP
values follow the 200GeV RHIC results closely in the available transverse momentum range for all particle species. For π
± above 2.5GeV/c transverse momentum, the measured suppression is smaller than that observed at RHIC. The nuclear modification
factor R
AA/pA
for π
± stays well below unity. 相似文献
19.
Alexander Bazilevsky 《Acta Physica Hungarica A》2004,21(2-4):101-105
We present PHENIX recent results on charged particle and transverse energy densities measured at mid-rapidity in Au?Au collisions at $\sqrt {s_{NN} } = 130$ GeV and 200 GeV over a broad range of centralities. The mean transverse energy per charged particle is derived. The first PHENIX measurements at $\sqrt {s_{NN} } = 19.6$ GeV are also presented. A comparison with calculations from various theoretical models is performed. 相似文献
20.
Thomas S. Ullrich 《Acta Physica Hungarica A》2004,21(2-4):143-150
Inclusive spectra of charged particles at midrapidity in Au+Au collisions at $\sqrt {s_{NN} } = 130$ GeV and 200 GeV were measured with the STAR detector at RHIC. The measured mean transverse momentum 〈p T 〉 shows a characteristic dependence on charged particle multiplicity and beam energy in Au+Au collisions that is distinctly different from pp, $p\bar p$ and e+e? collisions. A 32%±3%(syst) increase in 〈p T 〉 from pp to Au+Au collisions was observed at 200 GeV. While the charged multiplicity was found to increase by 19%±5%(syst) from $\sqrt {s_{NN} } = 130$ GeV to 200 GeV, no significant difference in 〈p T 〉 was found between the two energies. A comparison with model predictions is discussed. 相似文献