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Microscopic study of freeze-out in relativistic heavy ion collisions at SPS energies

L. V. Bravina·I. N. Mishustin·J. P. Bondorf·Amand Faessler·E. E. Zabrodin
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Abstract

The freeze-out conditions in the light (S+S) and heavy (Pb+Pb) colliding systems of heavy nuclei at 160 AGeV/$c$ are analyzed within the microscopic Quark Gluon String Model (QGSM). We found that even for the most heavy systems particle emission takes place from the whole space-time domain available for the system evolution, but not from the thin ''freeze-out hypersurface", adopted in fluid dynamical models. Pions are continuously emitted from the whole volume of the reaction and reflect the main trends of the system evolution. Nucleons in Pb+Pb collisions initially come from the surface region. For both systems there is a separation of the elastic and inelastic freeze-out. The mesons with large transverse momenta, $p_t$, are predominantly produced at the early stages of the reaction. The low $p_t$-component is populated by mesons coming mainly from the decay of resonances. This explains naturally the decreasing source sizes with increasing $p_t$, observed in HBT interferometry. Comparison with S+S and Au+Au systems at 11.6 AGeV/$c$ is also presented.

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L. V. Bravina, I. N. Mishustin, J. P. Bondorf, Amand Faessler, E. E. Zabrodin. 1999-07-15. Microscopic study of freeze-out in relativistic heavy ion collisions at SPS energies. https://doi.org/10.1103/physrevc.60.044905

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