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Reconstructing the Freeze-out State in Pb+Pb Collisions at 158 AGeV/c

Boris Tomasik·Urs Achim Wiedemann·Ulrich Heinz
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Abstract

For a class of analytical parametrizations of the freeze-out state of relativistic heavy ion collisions, we perform a simultaneous analysis of the single-particle m_t-spectra and two-particle Bose-Einstein correlations measured in central Pb+Pb collisions at the CERN SPS. The analysis includes a full model parameter scan with chi^2 confidence levels. A comparison of different transverse density profiles for the particle emission region allows for a quantitative discussion of possible model dependencies of the results. Our fit results suggest a low thermal freeze-out temperature T approximately 95 +- 15 MeV and a large average transverse flow velocity of about 0.55c +- 0.07c. Moreover, the fit favours a box-shaped transverse density profile over a Gaussian one. We discuss the origins and the consequences of these results in detail. In order to reproduce the measured pion multiplicity our model requires a positive pion chemical potential. A study of the pion phase-space density indicates μ_πapproximately 60 MeV for T = 100 MeV.

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Boris Tomasik, Urs Achim Wiedemann, Ulrich Heinz. 1999-07-23. Reconstructing the Freeze-out State in Pb+Pb Collisions at 158 AGeV/c. https://doi.org/10.1556/aph.17.2003.1.11

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