2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/199014Freeze out of particles across a space-time hypersurface is discussed in kinetic models. The calculation of final momentum distribution of emitted particles is described for freeze out surfaces, with spacelike normals. The resulting non-equilibrium distribution does not resemble, the previously proposed, cut Juttner distribution, and shows non-exponential p_t-spectra similar to the ones observed in experiments.24 pages, 8 figures, submitted to Heavy Ion PhysicsNuclear Theorytext