Figure. The strange baryon to negative charged hadron ratios and doubly to singly strange ratio as a function of sqrt(s) for the most central Au-Au and Pb-Pb collisions. The solid lines are the statistical uncertainties while the caps indicate the systematic uncertainty on each measurement.

The anti-Xi and anti-Lambda to h- ratios for the most central Au-Au data increase when compared to the most central SPS energies. However, the Xi/h- ratio stays constant and the Lambda/h- even decreases. These seemingly different trends are a result of the interplay between the net-baryon number, which reduces significantly from the SPS to RHIC, and the increase in total strangeness production from SPS to RHIC. At RHIC the net-baryon number at mid-rapidity is virtually zero, this causes the Xi/h- ratio to be approximately equal to that of the anti-Xi/h- at these energies. The SPS anti-Lambda/Lambda ratio is 0.13 while at RHIC in Au-Au collisions at 130 GeV/c it is 0.71. This dramatic decrease in the net-baryon number has a stronger effect on the Lambda than on the Xi which causes the Xi/Lambda ratio to increase at RHIC. The anti-Xi/anti-Lambda ratio meanwhile stays constant. This ratio is independent of the number of baryons transported from the colliding nuclei and hence indicates that although the yields of the strange baryons increase from SPS to RHIC the scale of the enhancement of multi-strange baryons is the same as for the singly strange.

Mid-rapidity Lambda and Lambda bar Production in Au + Au Collisions at sqrt(s_nn) = 130 GeV
Phys. Rev. Lett. 89 (2002) 092301
e-Print Archives (nucl-ex/0203016): Abstract | PS | PDF
Journal article: Phys. Rev. Lett. server

Multi-strange baryon production in Au-Au collisions at sqrt(s_nn) = 130 GeV
Phys. Rev. Lett. 92 (2004) 182301
e-Print Archives (nucl-ex/0307024): Abstract | PS | PDF
Journal article: Phys. Rev. Lett. server