An excitation function at the AGS: E917 — Probing the dynamics of heavy ion collisions

Seto, R.; Back, B. B.; Betts, R. R.; Britt, H. C.; Chang, James; Chang, W. C.; Chi, C.Y.; Chu, Y. Y.; Cumming, J. B.; Dunlop, J. C.; Eldredge, W.; Fung, S. Y.; Ganz, R.; Garcia-Solis, E. J.; Gillitzer, A.; Heintzelman, G.; Henning, W.; Hofman, D. J.; Holzman, B.; Kang, J. H.; Kim, E.J.; Kim, S.Y.; Kwon, Y.-J.; McLeod, D.; Mignerey, A. C.; Moulson, M.; Nanal, V.; Ogilvie, C. A.; Pak, R.; Ruangma, A.; Russ, D.; Stanskas, P. J.; Stephans, G. S. F.; Wang, H.Q.; Wolfs, F. L. H.; Wuosmaa, A. H.; Xiang, H.; Xu, G.; Yao, H.; Zou, C.

doi:10.1016/s0375-9474(98)00399-6

Cited by 4 publications

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“…The central topic of relativistic heavy ion physics is the study of Quantum Chromodynamics (QCD) in extreme conditions of high temperature and high energy density over large volumes 1 . Vector mesons may probe the dynamics of particles and chiral symmetry 2 in relativistic heavy ion collisions: their production mechanisms and subsequent dynamical evolution have been a topic of experimental investigation 3,4,5,6 . The φ meson is of particular interest due to its ss valence quark content, which may make the φ sensitive to strangeness production from a possible early partonic phase 7,8,9 . In central P b + P b collisions at the CERN SPS (nucleon-nucleon center of mass energy √ s N N ≃ 17 GeV), the slope parameter (T ) in an exponential fit to the transverse mass (m t ) distribution at mid-rapidity (∝ e −mt/T ) follows a systematic trend as a function of hadron mass for pions, kaons and protons 11 .…”

Section: Introductionmentioning

confidence: 99%

Resonance Production at Star

Yamamoto

2002

Multiparticle Dynamics

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We present the first measurement of mid-rapidity φ vector meson production in Au + Au collisions at RHIC ( √ s N N = 130 GeV) from the STAR detector. For the 11% most central collisions, the slope parameter from an exponential fit to the transverse mass distribution is T = 379±51(stat)± 45(syst) MeV, the yield dN/dy = 5.73±0.37(stat)± 0.57(syst) per event and the ratio N φ /N h − is found to be 0.021±0.001(stat)± 0.004(syst). We currently place the value of the N φ /N K − ratio between 0.10 and 0.16. The measured ratios N φ /N h − and N φ /N K − , as well as T for the φ meson at mid-rapidity do not change for the selected centrality bins.

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Section: Introductionmentioning

confidence: 99%

Resonance Production at Star

Yamamoto

2002

Multiparticle Dynamics

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“…Naively one would expect that increasing beam energy leads to higher energy deposition in the reaction zone and thus to higher temperature and/or stronger radial flow at freeze-out. A tendency for stronger flow at larger √ s is indeed seen at energies below and including the AGS [20,21]. At the higher SPS energy an analysis of negative particle spectra and two-particle correlations from the NA49 Pb+Pb experiment points to kinetic freezeout at T =100−120 MeV with v ⊥ =0.45−0.5 c [22,23], the lower freeze-out temperature and larger flow being preferred [23].…”

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Kinetic freeze-out and radial flow in 11.6 A GeV Au+Au collisions

1999

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We study the kinetic freeze-out conditions of hadrons in Au+Au collisions at 11.6 A GeV/c using different parametrizations of an expanding thermal fireball. We take into account the available double differential momentum spectra of a variety of particle species, covering a large fraction of the total momentum space. The overall fit to the data is very good and indicates a relatively low kinetic freeze-out temperature of about 90 MeV with an average transverse expansion velocity at midrapidity of about 0.5 c.PACS numbers: 25.75.Ld, 24.10.Pa When studying the nuclear phase diagram in extreme regions of temperature and density with heavy-ion collisions one is faced with the difficulty that, due to the limited size and strong dynamics of the fireballs created in such collisions, full (global) thermodynamic equilibrium and the thermodynamic (infinite volume) limit can never be reached. The best one can hope for is a state of local thermal equilibrium in a hydrodynamically expanding environment, with thermodynamic homogeneity volumes of several 100 to 1000 fm 3 [1]. If sufficient local equilibration is achieved one can try to extrapolate from the experimental findings to the thermodynamic limit. The most exciting prospect of such an endeavour is the experimental confirmation of a deconfinement phase transition in hot and dense nuclear matter [2].In order to reach this goal an extensive experimental program has been launched studying heavy-ion collisions at various beam energies. The onset of a new phase of nuclear matter would probably be most clearly seen in a study of different observables as functions of beam energy. For this purpose it is necessary to carefully analyze the data at all available beam energies. Here we present a study of the experimental particle spectra from Au+Au collision at a beam momentum of 11.6 A GeV/c measured by several groups [3][4][5] at the Brookhaven AGS. The goal is to find a simple, but realistic parametrization of the freeze-out stage in these collisions. The extracted freezeout parameters, especially the temperature and the mean transverse flow velocity, will be compared with other collision systems and with collisions at different energies. * On leave from Institut für Theoretische Physik, Universität Regensburg; email address: Ulrich.Heinz@cern.chThis should help to understand the gross features of the collision dynamics at ultrarelativistic energies.For the description of particle production we start from the formalism of Cooper and Frye [6] which describes the single-particle spectrum as an integral over a freeze-out hypersurface, thus summing the contributions from all space-time points at which the particles decouple from the fireball:Here g is the degeneracy factor and f (x, p) the momentum distribution at space-time point x. In thermal models one uses for f (x, p) a thermal equilibrium distribution and determines Σ f by a freeze-out criterium for thermal decoupling [7]. For the low temperatures discussed below the Boltzmann approximation is sufficient, but we allow for a...

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Search for medium modifications of hadrons with hadronic observables

Gillitzer

1999

Progress in Particle and Nuclear Physics

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An excitation function at the AGS: E917 — Probing the dynamics of heavy ion collisions

Cited by 4 publications

References 3 publications

Resonance Production at Star

Resonance Production at Star

Kinetic freeze-out and radial flow in 11.6 A GeV Au+Au collisions

Search for medium modifications of hadrons with hadronic observables

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