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Conclusion from NA44 strangeness measurements

Production of charged $K$ and $\pi$ mesons in central Pb+Pb collisions at 158 GeV/nucleon has been measured. Within the centrality range studied, no strong multiplicity dependence of the kaon $m_T$ slopes or $K/\pi$ ratios has been observed. We see no significant slope difference between $K^+$ and $K^-$. $K^+/\pi ^+$ is enhanced by a factor of about two over $p+p$ collisions, whereas $K^-/\pi^-$ is little enhanced. Our measurement of $K^+/K^-$ in this saturated region may be used for chemical calculations of the hadron gas.

Comparison with the RQMD model shows that the model qualitatively reproduces the hadron chemistry, through the rescattering of the produced particles. Quantitative comparisons, however, show that the model overpredicts the $K^-$, while the magnitude of $K^+$ enhancement is within the range explainable by the RQMD mechanisms. Deconfinement scenarios of the $K^+/\pi ^+$ enhancement can not, however, be ruled out or proven by the NA44 data alone. Non-NA44 measurements of strange particles less common than kaons do not clarify the picture and the overall impression is that

• an overprediction of a (multi)strange (anti)baryon yield is the most frequent outcome for both VENUS and RQMD
• the rarer the particle, the less reliable the theoretical predictions, based on dynamical modes, become