共查询到20条相似文献,搜索用时 515 毫秒
1.
Felix Matathias 《Acta Physica Hungarica A》2006,25(2-4):303-312
Measurements of identified particle production with the PHENIX experiment at RHIC have reached a mature state, where a multitude of nuclear systems at different colliding energies have been studied. The discovery configurations of $\sqrt {s_{NN} } = 130$ and 200 GeV Au+Au collisions have now been supplemented by additional Au+Au and Cu+Cu configurations at various energies, along with baseline p+p and d+Au runs at $\sqrt {s_{NN} } = 130$ GeV. In this work we present a systematic study of the Cronin effect in d+Au collisions and recent results from p+p collisions. We then proceed to make a critical comparison of pion, kaon and proton production in heavy ion and baseline systems, and discuss the observed nuclear effects on hadron production. 相似文献
2.
M. Zawisza 《Physics of Particles and Nuclei Letters》2011,8(9):924-927
Correlations between non-identical particles at small relative velocity probe asymmetries in the average space-time emission
points at freeze-out. The origin of such asymmetries may be from long-lived resonances, bulk collective effects, or differences
in the freeze-out scenario for the different particle species. STAR has extracted pion-proton correlation functions from a
dataset of Au+Au collisions at √s
NN
= 200 GeV. We present correlation functions in the spherical harmonic decomposition representation, for different centralities
and for different combinations of pions and (anti-)protons. 相似文献
3.
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
4.
F. Retière 《Acta Physica Hungarica A》2004,19(3-4):369-372
Ultra-relativistic heavy-ion collisions produced at RHIC differ significantly from a superposition of proton-proton collisions. Evidence of collective expansion has been gathered. The yield of high transverse momentum particles has been found to be lower in head-on Au?Au collisions than is expected by scaling p-p collisions. Di-jet processes, which are frequent in p-p collisions, are almost absent in head-on Au?Au collisions. The current results from RHIC indicate that Au?Au collisions at $\sqrt {S_{NN} } = 130$ GeV and $\sqrt {S_{NN} } = 200$ GeV yield an expanding system that is opaque to high momentum partons. 相似文献
5.
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
6.
J. C. Dunlop 《Acta Physica Hungarica A》2004,21(2-4):215-220
We report high statistics measurements of inclusive charged hadron production in Au+Au collisions at $\sqrt {s_{NN} } = 200$ GeV and 130 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for 5 ‖p T ‖ 12 GeV/c. The collision energy dependence of the yields and the centrality and p T dependence of the suppression provide stringent constraints on theoretical models of suppression. Models incorporating initial-state gluon saturation or partonic energy loss in dense matter are largely consistent with observations. The p T -dependent suppression expected from models incorporating jet attenuation in cold nuclear matter or absorption of fragmentation hadrons is not observed. 相似文献
7.
Adams J Aggarwal MM Ahammed Z Amonett J Anderson BD Anderson M Arkhipkin D Averichev GS Bai Y Balewski J Barannikova O Barnby LS Baudot J Bekele S Belaga VV Bellingeri-Laurikainen A Bellwied R Bezverkhny BI Bhardwaj S Bhasin A Bhati AK Bichsel H Bielcik J Bielcikova J Bland LC Blyth CO Blyth SL Bonner BE Botje M Bouchet J Brandin AV Bravar A Bystersky M Cadman RV Cai XZ Caines H Calderón de la Barca Sánchez M Castillo J Catu O Cebra D Chajecki Z Chaloupka P Chattopadhyay S Chen HF Chen JH 《Physical review letters》2007,98(6):062301
We present the scaling properties of Lambda, Xi, and Omega in midrapidity Au+Au collisions at the Brookhaven National Laboratory Relativistic Heavy Ion Collider at sqrt[s_{NN}]=200 GeV. The yield of multistrange baryons per participant nucleon increases from peripheral to central collisions more rapidly than that of Lambda, indicating an increase of the strange-quark density of the matter produced. The strange phase-space occupancy factor gamma_{s} approaches unity for the most central collisions. Moreover, the nuclear modification factors of p, Lambda, and Xi are consistent with each other for 2相似文献
8.
Andrew Glenn 《Acta Physica Hungarica A》2006,25(2-4):381-388
Understanding normal nuclear medium effects present in heavy ion collisions is essential for understanding the following dynamics of the high density matter produced in the collision. Asymmetric collisions, such as deuteron + gold, provide a key tool for studying these effects since particles produced in the forward and backward directions may be subject to different phenomena. Particle production has been studied in d+Au collisions for various kinematic regions at the RHIC facility. PHENIX has measured charged hadron production as a function of pT for different centrality classes using the PHENIX muon spectrometers for d+Au collisions at $\sqrt {s_{NN} } = 200$ GeV. The PHENIX muon spectrometers have coverage in both forward and backward directions in the rapidity range 1.2 |η| < 2.4. The R cp measurement, the ratio of central to peripheral production, is presented and discussed. Comparisons are also made with some relevant theoretical calculations. 相似文献
9.
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
10.
Jian Tian 《Central European Journal of Physics》2012,10(6):1365-1368
We present measurements of event-by-event fluctuations on hadron multiplicity ratios (K/??, p/??, K/p) in Au+Au collisions at $\sqrt {s_{NN} } $ and 200 GeV using the STAR detector at RHIC. The magnitude of dynamical fluctuations ?? dyn for p/?? and K/p ratios change smoothly from a large negative value at 7.7 GeV to a smaller negative value at 200 GeV while that for the K/?? ratios exhibits no significant beam energy dependence. The dynamical fluctuations related to pair production ?? dyn pair dyn for the p/K, K/p, K ?/K + and p/p ratios at 200 GeV all exhibit a maximum at the mid-central collisions and decrease at the most peripheral and most central collisions. 相似文献
11.
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
12.
Brooke Haag 《Indian Journal of Physics》2011,85(1):123-127
Di-hadron correlation measurements have been used to probe di-jet production in heavy ion collisions at RHIC. A strong suppression
of the away-side high-p
T
yield in these measurements is direct evidence that high-p
T
partons lose energy as they traverse the strongly interacting medium. However, since the momentum of the trigger particle
is not a good measure of the jet energy, azimuthal di-hadron correlations have limited sensitivity to the shape of the fragmentation
function. We explore the possibility to better constrain the initial parton energy by using clusters of multiple high-p
T
hadrons in a narrow cone as the ‘trigger particle’ in the azimuthal correlation analysis. We present first results from this
analysis of multi-hadron triggered correlated yields in Au+Au collisions at $
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 200 GeV from STAR. The results are compared with measurements in d + Au collisions and Pythia calculations, and the implications for energy loss and jet fragmentation are discussed. 相似文献
13.
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
14.
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
15.
A. P. Mishra R. K. Mohapatra P. S. Saumia A. M. Srivastava 《Indian Journal of Physics》2011,85(6):909-915
We focus on the initial state spatial anisotropies, originating at the thermalization stage, for central collisions in relativistic
heavy-ion collisions. We argue that the physics of fluctuations at the early stages of heavy ion collisions has strong similarities
with the physics of density fluctuations in the early universe which give rise to remarkable acoustic peaks in the cosmic
microwave background radiation (CMBR) power spectrum. Following the method of analysis in CMBR physics, we propose that a
plot of root mean square values of the flow coefficients ?{[`(vn2 )] } o vnrms\sqrt {\overline {v_n^2 } } \equiv v_n^{rms} , calculated in a laboratory fixed coordinate system, for a large range of n from 1 to about 30, can give non-trivial information about the initial stages of the system and its evolution.
We also argue that for all wavelengths λ of the anisotropy (at the surface of the plasma region) much larger than the acoustic horizon size Hsfr H_s^{f^r } at the freezeout stage, the resulting values of V
n
mns
should be suppressed by a factor of order 2Hsfr /l2H_s^{f^r } /\lambda . 相似文献
16.
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
17.
M. Sharma 《Indian Journal of Physics》2011,85(6):855-860
We present measurements of net charge fluctuations in Au + Au collisions at ?{sNN }\sqrt {s_{NN} } = 19.6, 62.4, 130, and 200 GeV, Cu + Cu collisions at ?{sNN }\sqrt {s_{NN} } = 62.4, 200 GeV, and p + p collisions at ?s\sqrt s = 200 GeV using the net charge dynamical fluctuations measure ν+ −,dyn. The dynamical fluctuations are non-zero at all energies and exhibit a rather modest dependence on beam energy. We find that
at a given energy and collision system, net charge dynamical fluctuations violate 1/N
ch
scaling, but display approximate 1/N
part
scaling. We observe strong dependence of dynamical fluctuations on the azimuthal angular range and pseudorapidity widths. 相似文献
18.
Afanasiev S Aidala C Ajitanand NN Akiba Y Alexander J Al-Jamel A Aoki K Aphecetche L Armendariz R Aronson SH Averbeck R Awes TC Azmoun B Babintsev V Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bauer F Bazilevsky A Belikov S Bennett R Berdnikov Y Bjorndal MT Boissevain JG Borel H Boyle K Brooks ML Brown DS Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Campbell S Chai JS Chernichenko S Chiba J Chi CY Chiu M Choi IJ Chujo T Cianciolo V Cleven CR 《Physical review letters》2008,101(8):082301
Measurements in Au+Au collisions at sqrt[s_{NN}]=200 GeV of jet correlations for a trigger hadron at intermediate transverse momentum (p_{T,trig}) with associated mesons or baryons at lower p_{T,assoc} indicate strong modification of the away-side jet. The ratio of jet-associated baryons to mesons increases with centrality and p_{T,assoc}. For the most central collisions, the ratio is similar to that for inclusive measurements. This trend is incompatible with in-vacuum fragmentation but could be due to jetlike contributions from correlated soft partons, which recombine upon hadronization. 相似文献
19.
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