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star physics results: Strange particles

Note: Click on a figure for a larger version.

Figure. K/Pi ratio at mid-rapidity as a function of sqrt(s). The curves are a parameterization of the p-p data. The STAR data points are indicated by the caps and the STAR K+/pi ratio is displaced slightly to clarity.

Systematics of the K/pi ratio

Kaons carry ~90% of the strange quarks produced in a collision hence the K/pi ratio can be used to study strangeness production and the possibility of strangeness enhancement. As the pi+yield ~ pi- yield it is possible to compare the STAR K+/pi- results to lower energy results on the K+/pi+. The K-/pi ratio can be seen to rise smoothly with sqrt(s) while that of K+/pi in heavy ion collisions increases sharply at low energies reaching a maximum at sqrt(s)~10GeV before slowly dropping. At sqrt(s)=130 GeV the K+/pi ~K-/pi. The peak is determined by the dropping net baryon value combining with increasing K anti-K pair production. Similar behaviour is observed in the strange baryon ratios. Comparisons to the p-p data at sqrt(s)=130 GeV shows a 50% increase in the STAR (K++K-)/2*<pi> ratio.

Related STAR papers
Kaon Production and Kaon to Pion Ratio in Au + Au Collisions at sqrt(snn) = 130 GeV
Phys. Lett. B 595 (2004) 143
e-Print Archives (nucl-ex/0206008): Abstract | PS | PDF
Journal article: Phys. Lett. B server

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