Strangeness Excitation Functions and Transition from Baryonic to Mesonic Freeze-Out

The sharp peak in the K+/pi+ ratio in relativistic heavy-ion collisions is discussed in the framework of the Statistical Model. In this model a rapid change is expected as the hadronic gas undergoes a transition from a baryon-dominated to a meson-dominated gas. The maximum in the Lambda/\pi$ ratio is well reproduced by the Statistical Model, but the change in the K+/pi+ ratio is somewhat less pronounced than the one observed by the NA49 collaboration. The calculated smooth increase of the K-/pi ratio and the shape of the Xi-/pi+ and Omega-/pi+ ratios exhibiting maxima at different incident energies is consistent with the presently available experimental data. We conclude that the measured particle ratios with $20-30%$ deviations agree with a hadronic freeze-out scenario. These deviations seem to occur just in the transition from baryon-dominated to meson-dominated freeze-out.