Non-equilibrated post-freeze-out distributions
Center for Physics of Fundamental Interactions (CFIF), Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
2 Section for Theoretical and Computational Physics, Department of Physics, University of Bergen, 5007, Allegaten 55, Norway
3 Parallab - High Performance Computing Laboratory, University of Bergen, Department of Informatics, 5020, Bergen, Norway
4 KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, 1525, Budapest, Hungary
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We discuss freeze-out on the hypersurface with time-like normal vector, trying to answer how realistic it is to assume thermal post-freeze-out distributions for measured hadrons. Using simple kinetic models for gradual freeze-out we are able to generate a thermal post-FO distribution, but only in a highly simplified situation. In a more advanced model, taking into account rescattering and re-thermalization, the post-FO distribution gets more complicated. The resulting particle distributions are in qualitative agreement with the experimentally measured pion spectra. Our study also shows that the obtained post-FO distribution functions, although analytically very different from the Jüttner distribution, do look pretty much like thermal distributions in some range of the parameters.
© Springer-Verlag, 2003