Strangeness production in heavy ion collisions at SPS and RHIC within   two-source statistical model
  The experimental data on hadron yields and ratios in central Pb+Pb and Au+Au collisions at SPS and RHIC energies, respectively, are analysed within a two-source statistical model of an ideal hadron gas. These two sources represent the expanding system of colliding heavy ions, where the hot central fireball is embedded in a larger but cooler fireball. The volume of the central source increases with rising bombarding energy. Results of the two-source model fit to RHIC experimental data at midrapidity coincide with the results of the one-source thermal model fit, indicating the formation of an extended fireball, which is three times larger than the corresponding core at SPS. 
Zhong-Dao Lu (1,2), Amand Faessler (2), C. Fuchs (2), E. Zabrodin   (2,3) ((1) China Institute of Atomic Energy, Beijing, Ch...