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Abstract

When chiral symmetry is restored in the quark-gluon plasma produced in relativistic heavy ion collisions, we argue that the yield ratio of K1 / K* mesons in these collisions is larger than the prediction of the statistical model as the chemical freeze-out temperature in this model is close to the chiral transition temperature. Since the mass difference of chiral partners, such as the K1 / K* mesons, serves as an order parameter of chiral phase transition, the yield of axial vector meson is enhanced when chiral symmetry is restored because its temperature-dependent mass approaches the vacuum mass of vector meson as shown in studies based on the QCD sum rules. We further demonstrate via a kinetic approach that, although the enhancement effect on the K1 / K* yield ratio is reduced during the hadronic phase of relativistic heavy ion collisions after the chemical freeze-out, the signal is still visible in peripheral collisions due to the higher kinetic freeze-out temperature and shorter hadronic lifetime than in central collisions. Including the non-unity hadron fugacities and temperature-dependent K1 mass in hadronic matter, calculations based on the kinetic approach are found to give a factor of 2.6 enhancement of the K1 / K* ratio compared to its value from the statistical model in peripheral collisions (70-80\%) of Pb+Pb at √sNN= 5.02 TeV.