$K_1/K^*$ enhancement as a signature of chiral symmetry restoration in heavy ion collisions

TL;DR

The paper proposes that the ratio of $K_1$ to $K^*$ mesons in heavy ion collisions can serve as a signature of chiral symmetry restoration, showing a significant enhancement due to the reduction of the chiral order parameter.

Contribution

It introduces the idea that the $K_1/K^*$ production ratio can indicate chiral symmetry restoration, providing a new observable for experimental verification.

Findings

$K_1/K^*$ ratio is predicted to be larger than statistical model predictions.

Enhancement signal varies with collision centrality and freeze-out temperature.

Systematic study can distinguish the chiral restoration signal from hadronic phase effects.

Abstract

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.