K+/π+enhancement in heavy-ion collisions

Using the expanding fireball model, we calculate the $K^{+}$/${\pi }^{+}$ ratio from heavy-ion collisions at 14.5 GeV/nucleon. A substantially larger ratio than that from the proton-nucleus collisions at the same energy is obtained if the contribution from the pion-pion interactions is included. This is supported by the preliminary data.