作者机构：
[Abelev, B. I.] Yale Univ, New Haven, CT 06520 USA.;Argonne Natl Lab, Argonne, IL 60439 USA.;Univ Birmingham, Birmingham, W Midlands, England.;Brookhaven Natl Lab, Upton, NY 11973 USA.;CALTECH, Pasadena, CA 91125 USA.
通讯机构：
[Abelev, B. I.] Y;Yale Univ, New Haven, CT 06520 USA.
作者：
Adams, J.*;Aggarwal, M. M.;Ahammed, Z.;Amonett, J.;Anderson, B. D.;...
期刊：
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS,2006年32(6):L37-L48 ISSN：0954-3899
通讯作者：
Adams, J.
作者机构：
[Adams, J.] Univ Birmingham, Birmingham, W Midlands, England.;Panjab Univ, Chandigarh 160014, India.;Ctr Variable Energy Cyclotron, Kolkata 700064, W Bengal, India.;Kent State Univ, Kent, OH 44242 USA.;Joint Inst Nucl Res Dubna, Particle Phys Lab, Dubna, Russia.
通讯机构：
[Adams, J.] U;Univ Birmingham, Birmingham, W Midlands, England.
摘要：
We present first measurements of the pseudorapidity and azimuth (eta, phi) bin-size dependence of event-wise mean transverse-momentum < pt > fluctuations for Au-Au collisions at root sNN = 200 GeV. We invert that dependence to obtain p(t) autocorrelations on differences (eta(Delta), phi(Delta)) interpreted to represent velocity/temperature distributions on (eta, phi). The general form of the autocorrelations suggests that the basic correlation mechanism is parton fragmentation. The autocorrelations vary rapidly with collision centrality, which suggests that fragmentation is strongly modified by a dissipative medium in the more central Au-Au collisions relative to peripheral or p-p collisions.
作者机构：
Argonne Natl Lab, Argonne, IL 60439 USA.;Univ Bern, CH-3012 Bern, Switzerland.;Univ Birmingham, Birmingham B15 2TT, W Midlands, England.;Brookhaven Natl Lab, Upton, NY 11973 USA.;CALTECH, Pasadena, CA 91125 USA.
通讯机构：
[Adams, J] A;Argonne Natl Lab, 9700 S Cass Ave, Argonne, IL 60439 USA.
摘要：
We present the directed flow (v(1)) measured in Au+Au collisions at root s(NN)=62.4 GeV in the midpseudorapidity region parallel to eta parallel to < 1.3 and in the forward pseudorapidity region 2.5 <parallel to eta parallel to < 4.0. The results are obtained using the three-particle cumulant method, the event plane method with mixed harmonics, and for the first time at the Relativistic Heavy Ion Collider, the standard method with the event plane reconstructed from spectator neutrons. Results from all three methods are in good agreement. Over the pseudorapidity range studied, charged particle directed flow is in the direction opposite to that of fragmentation neutrons.
期刊：
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS,2006年32(8):1121-1129 ISSN：0954-3899
通讯作者：
Lu, Y.
作者机构：
[Lu, Y.] Huazhong Normal Univ, Cent China Normal Univ, Inst Particle Phys, IOPP, Wuhan 430079, Peoples R China.;Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94720 USA.;Goethe Univ Frankfurt, Inst Theoret Phys, D-60438 Frankfurt, Germany.;Brookhaven Natl Lab, Upton, NY 11973 USA.;FIAS, D-60438 Frankfurt, Germany.
通讯机构：
[Lu, Y.] H;Huazhong Normal Univ, Cent China Normal Univ, Inst Particle Phys, IOPP, Wuhan 430079, Peoples R China.
摘要：
The transverse momentum dependence of the anisotropic flow $v_2$ for $\pi$, $K$, nucleon, $\Lambda$, $\Xi$ and $\Omega$ is studied for Au+Au collisions at $\sqrt{s_{\rm NN}} = 200$ GeV within two independent string-hadron transport approaches (RQMD and UrQMD). Although both models reach only 60% of the absolute magnitude of the measured $v_2$, they both predict the particle type dependence of $v_2$, as observed by the RHIC experiments: $v_2$ exhibits a hadron-mass hierarchy (HMH) in the low $p_T$ region and a number-of-constituent-quark (NCQ) dependence in the intermediate $p_T$ region. The failure of the hadronic models to reproduce the absolute magnitude of the observed $v_2$ indicates that transport calculations of heavy ion collisions at RHIC must incorporate interactions among quarks and gluons in the early, hot and dense phase. The presence of an NCQ scaling in the string-hadron model results suggests that the particle-type dependencies observed in heavy-ion collisions at intermediate $p_T$ might be related to the hadronic cross sections in vacuum rather than to the hadronization process itself. Comment: 10 pages, 5 figures; A new author (H. Petersen) is added; A new figure (fig.1) on time evolution of elliptic flow and number of collisions is added; Version accepted for publication in J. Phys. G
摘要：
We present the first measurement of pseudorapidity distribution of photons in the region 2.3 < or = eta < or = 3.7 for different centralities in Au+Au collisions at square root of (S(NN)) = 62.4 GeV. We find that the photon yield scales with the number of participating nucleons at all collision centralities studied. The pseudorapidity distribution of photons, dominated by pi0 decays, has been compared to those of charged pions, photons, and inclusive charged particles from heavy-ion and nucleon-nucleon collisions at various energies. The photon production has been shown to be consistent with the energy and centrality independent limiting fragmentation scenario.
作者机构：
Argonne Natl Lab, Argonne, IL 60439 USA.;Brookhaven Natl Lab, Upton, NY 11973 USA.;Univ Birmingham, Birmingham, W Midlands, England.;Univ Calif Davis, Davis, CA 95616 USA.;Univ Calif Los Angeles, Los Angeles, CA 90095 USA.
通讯机构：
[Adams, J] A;Argonne Natl Lab, 9700 S Cass Ave, Argonne, IL 60439 USA.
摘要：
We present the first large-acceptance measurement of event-wise mean transverse momentum < p(t)> fluctuations for Au-Au collisions at nucleon-nucleon center-of-momentum collision energy root s(NN) = 130 GeV. The observed nonstatistical < p(t)> fluctuations substantially exceed in magnitude fluctuations expected from the finite number of particles produced in a typical collision. The r.m.s. fractional width excess of the event-wise < p(t)> distribution is 13.7 +/- 0.1(stat) +/- 1.3(syst)% relative to a statistical reference, for the 15% most-central collisions and for charged hadrons within pseudorapidity range vertical bar eta vertical bar < 1,2 pi azimuth, and 0.15 <= p(t) <= 2 GeV/c. The width excess varies smoothly but nonmonotonically with collision centrality and does not display rapid changes with centrality which might indicate the presence of critical fluctuations. The reported < p(t)> fluctuation excess is qualitatively larger than those observed at lower energies and differs markedly from theoretical expectations. Contributions to < p(t)> fluctuations from semihard parton scattering in the initial state and dissipation in the bulk colored medium are discussed.
摘要：
We report the STAR measurement of phi meson production in Au + Au and p + p collisions at root s(NN) = 200 GeV. Using the event mixing technique, the phi spectra and yields are obtained at mid-rapidity for five centrality bins in Au + Au collisions and for non-singly-diffractive p + p collisions. It is found that the phi transverse momentum distributions from Au + An collisions are better fitted with a single-exponential while the p + p spectrum is better described by a double-exponential distribution. The measured nuclear modification factors indicate that phi production in central An + An collisions is suppressed relative to peripheral collisions when scaled by the number of binary collisions (< N-bin>). The systematics of < p(t)> versus centrality and the constant phi/K- ratio versus beam species, centrality, and collision energy rule out kaon coalescence as the dominant mechanism for phi production. (c) 2005 Elsevier B.V. All rights reserved.
摘要：
The short-lived K(892)* resonance provides an efficient tool to probe properties of the hot and dense medium produced in relativistic heavy-ion collisions. We report measurements of K* in root s(NN)=200 GeV Au+Au and p+p collisions reconstructed via its hadronic decay channels K(892)*(0)-> K pi and K(892)*(+/-)-> K(S)(0)pi(+/-) using the STAR detector at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The K*(0) mass has been studied as a function of p(T) in minimum bias p+p and central Au+Au collisions. The K-* p(T) spectra for minimum bias p+p interactions and for Au+Au collisions in different centralities are presented. The K*/K yield ratios for all centralities in Au+Au collisions are found to be significantly lower than the ratio in minimum bias p+p collisions, indicating the importance of hadronic interactions between chemical and kinetic freeze-outs. A significant nonzero K*(0) elliptic flow (v(2)) is observed in Au+Au collisions and is compared to the K-S(0) and Lambda v(2). The nuclear modification factor of K* at intermediate p(T) is similar to that of K-S(0) but different from Lambda. This establishes a baryon-meson effect over a mass effect in the particle production at intermediate p(T) (2 < p(T)<= 4 GeV/c).
作者机构：
[Hallman, TJ] Brookhaven Natl Lab, Upton, NY 11973 USA.;Argonne Natl Lab, Argonne, IL 60439 USA.;Univ Bern, CH-3012 Bern, Switzerland.;Univ Birmingham, Birmingham B15 2TT, W Midlands, England.;CALTECH, Pasadena, CA 91125 USA.
通讯机构：
[Hallman, TJ] B;Brookhaven Natl Lab, Upton, NY 11973 USA.
摘要：
We review the most important experimental results from the first three years of nucleus-nucleus collision studies at RHIC, with emphasis on results from the STAR experiment, and we assess their interpretation and comparison to theory. The theory-experiment comparison suggests that central Au + Au collisions at RHIC produce dense, rapidly thermalizing matter characterized by: (1) initial energy densities above the critical values predicted by lattice QCD for establishment of a quark-gluon plasma (QGP); (2) nearly ideal fluid flow, marked by constituent interactions of very short mean free path, established most probably at a stage preceding hadron formation; and (3) opacity to jets. Many of the observations are consistent with models incorporating QGP formation in the early collision stages, and have not found ready explanation in a hadronic framework. However, the measurements themselves do not yet establish unequivocal evidence for a transition to this new form of matter. The theoretical treatment of the collision evolution, despite impressive successes, invokes a suite of distinct models, degrees of freedom and assumptions of as yet unknown quantitative consequence. We pose a set of important open questions, and suggest additional measurements, at least some of which should be addressed in order to establish a compelling basis to conclude definitively that thermalized, deconfined quark-gluon matter has been produced at RHIC. (c) 2005 Published by Elsevier B.V.
摘要：
Identified mid-rapidity particle spectra of pi(+/-), K+/-, and p((p) over bar) from 200 GeV p + p and d + Au collisions are reported. A time-of-flight detector based on multi-gap resistive plate chamber technology is used for particle identification. The particle-species dependence of the Cronin effect is observed to be significantly smaller than that at lower energies. The ratio of the nuclear modification factor (R-dAu) between protons (p + (p) over bar) and charged hadrons (h) in the transverse momentum range 1.2 < p(T) < 3.0 GeV/c is measured to be 1.19 +/- 0.05(stat) +/- 0.03(syst) in minimum-bias collisions and shows little centrality dependence. The yield ratio of (p + (p) over bar)/h in minimum-bias d + Au collisions is found to be a factor of 2 lower than that in Au + Au collisions, indicating that the Cronin effect alone is not enough to account for the relative baryon enhancement observed in heavy ion collisions at RHIC. (c) 2005 Elsevier B.V. All rights reserved.
