1. Two-particle correlations... 2. Progress in... 3. Two- and three-particle interferometry... 4. Studies of HBT capabilities...

by CERN

Friday 18 Oct 2002, 09:30 → 10:30 Europe/Zurich

160/1-009 (CERN)

1. Two-particle correlations and dynamical timescales at RHIC Mike Lisa (Ohio State Univercity) The extreme conditions achieved in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are expected to trigger a phase transition from normal hadronic matter to the quark-gluon plasma (QGP), in which partonic degrees of freedom are relevant over large lengthscales. Identifying and studying this phase of matter is the central goal of the RHIC program. Crucial to this goal is a reliable theoretical framework for understanding the complex early dynamics of the collisions. The early and striking quantitative success of hydrodynamics in describing low-pt (<~2 GeV/c) momentum-space observables at RHIC raised the hope that such a tool was at hand. However, observables such as Hanbury-Brown/Twiss interferometry (HBT), which are sensitive to the spacetime evolution of the system, are poorly reproduced by hydro and other 'sensible' collision models; this is the so-called 'RHIC HBT puzzle.' I will briefly review the low-pt data and discuss HBT and other experimental observables sensitive to dynamical timescales. Although quantitative extraction of the various timescales is model/parameterization-dependent, STAR results consistently point towards very short evolution and freezeout times, suggesting a more explosive collision scenario than expected based on most existing models. 2. Progress in Correlation Femtoscopy Richard Lednicky (Institute for Nuclear Research, Dubna and Institute of Physics ASCR, Prague) Recent results on particle momentum and spin correlations are discussed, particularly, in view of the role played by the effect of final state interaction. It is demonstrated that this effect allows for (i) correlation femtometry with unlike particles (similar to the effect of quantum statistics); (ii) study of the relative space--time asymmetries in the production of different particle species (sensitive to collective flows and relative time delays); (iii) study of particle scattering for the systems hardly accessible by other means (e.g., for LambdaLambda system). 3. Two- and three-particle interferometry from the WA98 experiment in central 158 A GeV/c Pb+Pb collisions Laurent Rosselet (Geneva Univercity) Bose-Einstein correlations between two identified negative pions have been analysed as a function of kT, using two different parameterizations. The results indicate that the source does not have a strictly boost invariant expansion or spend time in a long-lived intermediate phase. A comparison between data and a hydrodynamical based simulation shows very good agreement for the radii parameters as a function of kT. The pion phase-space density at freeze-out has been measured and agrees well with the Tomasik-Heinz model. A large pion chemical potential close to the condensation limit of the pion mass seems to be excluded. The three-pion Bose-Einstein interferometry shows a substantial contribution of the genuine three-pion correlation, but not quite as large as expected for a fully chaotic and symmetric source. 4. Studies of HBT capabilities of Alice: current status Piotr Krzysztof Skowronski (CERN) Currently used simulation and analysis tools are described. First results of Alice HBT capabilties, obtained with current detector simulation and reconstruction software framework (AliRoot), are presented. Future plans and possibilities of further studies are discussed.

Organiser(s): Yiota Foka, Urs Wiedemann and Guy Paic

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