  Based on the fact that the mass difference between the chiral partners is an
order parameter of chiral phase transition and that the chiral order parameter
reduces substantially at the chemical freeze-out point in ultra-relativistic
heavy ion collisions, we argue that the production ratio of $K_1$ over $K^*$ in
such collisions should be substantially larger than that predicted in the
statistical hadronization model. We further show that while the enhancement
effect might be contaminated by the relatively larger decrease of $K_1$ meson
than $K^*$ meson during the hadronic phase, the signal will be visible through
a systematic study on centrality as the kinetic freeze-out temperature is
higher and the hadronic life time shorter in peripheral collisions than in
central collisions.
