Haesom Sung

We extend the recent study of $K_1/K^{*}$ enhancement as a signature of chiral symmetry restoration in heavy ion collisions at the CERN Large Hadron Collider via the kinetic approach to include the effects due to nonunity hadron fugacities during the evolution of produced hadronic matter and the temperature-dependent $K_1$ mass. Although including nonunity pion and kaon fugacities reduces slightly the $K_1/K^{*}$ enhancement found in previous study due to chiral symmetry restoration, adding temperature-dependent $K_1$ mass leads to a substantial further reduction of the $K_1/K^{*}$ enhancement. However, the final $K_1/K^{*}$ ratio still shows a factor of 2.4 and 1.3 enhancement, respectively, in peripheral and midcentral collisions compared to the case without chiral symmetry restoration, confirming its use as a good signature for chiral symmetry restoration in the hot dense matter produced in relativistic heavy ion collisions.

We extend the recent study of $K_{1}/K^{*}$ enhancement as a signature of chiral symmetry restoration in heavy ion collisions at the Large Hadron Collider (LHC) via the kinetic approach to include the effects due to non-unity hadron fugacities during the evolution of produced hadronic matter and the temperature-dependent $K_1$ mass. Although the effect of non-unity fugacity only slightly reduces the $K_1/K^*$ enhancement due to chiral symmetry restoration, the inclusion of the temperature-dependent $K_1$ mass leads to a substantial reduction in the $K_1/K^*$ enhancement. However, the final $K_1/K^*$ ratio in peripheral collisions still shows a more than factor of two enhancement compared to the case without chiral symmetry restoration and thus remains a good signature for chiral symmetry restoration in the hot dense matter produced in relativistic heavy ion collisions.

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.