Pionisation, relativistic lead-lead collisions, and the nature of average phase space density

The average phase space density (APSD) of the particles produced in high energy nuclear collisions at ultrarelativistic energies has here been theoretically estimated on the basis of some particular models for particle production spectra. The model-based values so obtained have been compared with the very recent experimental results in the field on the relevant observable and also with the calculated results obtained by some other models. Based on such comparisons, the present work indicates very strongly that Hagedorn's model has a sound potentiality to achieve a competitive status in its capability to deal with the data on the APSD factor in heavy-ion collisions. The impact and implications of all this have also been emphasised here in the end. Received: 14 November 2000 / Accepted: 19 April 2001