Rapidity and transverse momentum distributions in 6.4 TeV S+Pb interactions from CERN EMU05 experiments

Iyono, A.; Takahashi, Y.; Gregory, J. C.; Hayashi, T.; Shiina, T.; Christl, M. J.; Derrickson, J. H.; Fountain, W. F.; Parnell, T. A.; Rubin, B. C.; Watts, J. W.; Nagamiya, S.; Tominaga, T.; Dake, S.; Fuki, M.; Ogata, T.; Miyamura, O.; Yokomi, H.

doi:10.1016/0375-9474(92)90596-c

Cited by 6 publications

(1 citation statement)

References 11 publications

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“…This deficiency of pions for the preliminary data in Pb+Pb SPS collisions is not so drastic as in S+Pb SPS data, where the pion to nucleon ratio is close to 8 [15] and is approximately 2 times larger than the ideal gas result. To have an agreement with data in Figs.…”

Section: (34)mentioning

confidence: 67%

Excluded volume hadron gas model for particle number ratios inA+Acollisions

et al. 1997

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We recapitulate a thermodynamically consistent excluded volume hadron gas model and examine its differences with other "thermal models" used in the literature. Preliminary experimental data for particle number ratios in the collisions of Au+Au at the BNL AGS (11A GeV/c) and Pb+Pb at the CERN SPS (160A GeV/c) are analyzed. For equal values of the hadron hardcore parameters the excluded volume model gives essentially the ideal gas predictions for the particle number ratios, which is similar to other thermal models. We observe, however, the systematic excess of experimental pion abundances compared to the ideal gas results. This effect can be explained in our model by a smaller pion hard-core volume compared to those of other hadrons. The absolute values for particle number and energy densities at the chemical freezeout are predicted with a simultaneous fit to all these AGS and SPS particle number ratios. PACS number(s): 25.75.-q, 24.10.Pa Typeset using REVT E X

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Section: (34)mentioning

confidence: 67%

Excluded volume hadron gas model for particle number ratios inA+Acollisions

et al. 1997

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The excluded volume hadron gas model and pion production at the SPS

Ritchie

Gorenstein

Miller

1997

Zeitschrift f�r Physik C Particles and Fields

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Experimental data for nucleus-nucleus collisions at the CERN SPS suggest that an ideal hadron gas model is unable to account simultaneously (same baryonic chemical potential and temperature at freeze-out) for the strange anti-baryon to baryon ratios and pion abundances. Using a thermodynamically consistent excluded volume model we examine possibilities to account for the observed excess of pions.The formation of systems at high energies and densities allows the study of matter in another regime which, it is hoped, is amenable to the use of equilibrium statistical physics. Of particular interest is the possibility for the formation of a short-lived phase transition to a quark-gluon plasma (QGP). Recently nucleus-nucleus collisions have been performed at the BNL AGS (14 A GeV) and the CERN SPS (200 A GeV) producing energetic systems in which such a phase transition is hoped to take place. However, it is first necessary to understand predictions from conventional hadron physics before one can draw conclusions about any new phenomena which may be observed.Assuming local thermodynamical equilibrium at the final (freeze-out) stage of the process, particle number ratios can be calculated without detailed knowledge of the very complicated and poorly understood dynamics of heavy ion collisions. Strange particle production has attracted special attention as a possible signal of QGP formation [1, 2]. Hadron gas models have been successful in reproducing many of the observed hadron ratios measured at the AGS and SPS [3,4,5,6,7,8]. However for SPS data it has been observed [9, 4, 5, 6] that a simple ideal gas model is unable, within a single set of freeze-out parameters, to simultaneously yield the strange anti-baryon to baryon ratios together with pion to proton and charged particle ratios D Q = (N + − N − )/(N + + N − ) (N + and N − are the positive and negative charged hadron multiplicities). Note that N + − N − ∼ = p, N − ∼ = π − (p, π − are proton and negative pion multiplicities) and hence D Q ∼ = (1 + 2π − /p) −1 . It appears that the chemical freeze-out values of temperature T and baryonic chemical potential µ b found in Refs. [9,4,5,6] from the SPS data for strange particles are in a contradiction with the large pion/nucleon ratio. As D Q can be related to the entropy of the system, hadron gas models appear unable to account for the large entropy per baryon at freeze-out [9]. Therefore, unexpectedly, not strange particles but the deficiency of pions in the hadron gas model calculations is the main problem in the theoretical hadron gas interpretation of the SPS particle production data. Several mechanisms of the two-stage hadron chemical freeze-out [5] and QGP breakup to hadrons [9,5] have been proposed to remedy this problem but without significant success.The large values of T and µ b found in hadron gas models suggest that the chemical freeze-out state in the SPS experiments looks rather like a hot dense hadron gas and one needs a non-ideal gas equation of state to describe the system. In Refs. [7,8] a non-ideal fo...

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Thermal and hadrochemical equilibration in nucleus-nucleus collisions at the SPS

et al. 1996

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The currently available set of hadron abundances at the SPS for central S + Au(W,Pb) collisions is compared to predictions from a scenario assuming local thermal and hadrochemical equilibrium. The data are consistent with a freeze-out temperature T = 160 -170 MeV. Spectra are consistent with this temperature range and a moderate transverse expansion. The freeze-out points at the AGS and SPS are found to be close to the phase boundary between a hadron gas and an ideal quark-gluon phase.Studies of ultra-relativistic nucleus-nucleus collisions in fixed target experiments at the BNL AGS and CERN SPS investigate hadronic matter at extreme density. Nuclei at the AGS are found to stop each other completely in the c.m. frame, while at the SPS an onset of transparency is observed for S+A collisions [1]. It has been predicted [2] that the longest lived systems with high density are produced somewhere between AGS and SPS energies.Hadronic cascade models yield densities in the interior of the colliding nuclei up to ten times normal nuclear matter density [3]. An intriguing possibility is that the phase boundary to quark matter is crossed in these collisions. For zero net baryon density the transition

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Rapidity and transverse momentum distributions in 6.4 TeV S+Pb interactions from CERN EMU05 experiments

Cited by 6 publications

References 11 publications

Excluded volume hadron gas model for particle number ratios inA+Acollisions

Excluded volume hadron gas model for particle number ratios inA+Acollisions

The excluded volume hadron gas model and pion production at the SPS

Thermal and hadrochemical equilibration in nucleus-nucleus collisions at the SPS

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