Pseudoscalar neutral mesons in hot and dense matter

The behavior of neutral pseudoscalar mesons pi(0), eta and eta' in hot and dense matter is investigated, in the framework of the three flavor Nambu-Jona-Lasinio model. Three different scenarios are considered: zero density and finite temperature, zero temperature and finite density in a flavor asymmetric medium with and without strange valence quarks, and finite temperature and density. The behavior of mesons is analyzed in connection with possible signatures of restoration of symmetries. In the high density region and at zero temperature it is found that the mass of the eta' increases, the deviation from the mass of the 17 being more pronounced in matter without strange valence quarks. (C) 2003 Published by Elsevier Science B.V.