Freeze-out conditions for production of resonances, hadronic molecules, and light nuclei

TL;DR

This paper examines the freeze-out conditions in heavy ion collisions, revealing how they influence the production yields of resonances, molecules, and light nuclei, with implications for understanding particle suppression and formation.

Contribution

It introduces a kinetic freeze-out framework with hydrodynamic calculations to explain particle yield suppression and production mechanisms in heavy ion collisions.

Findings

Lower kinetic freeze-out temperature at LHC explains greater $K^*/K$ suppression.

Deuteron yields depend only on constituent number, not size.

Freeze-out conditions significantly affect light nuclei and molecular production.

Abstract

We investigate the freeze-out conditions of a particle in an expanding system of interacting particles in order to understand the productions of resonances, hadronic molecules and light nuclei in heavy ion collisions. Applying the kinetic freeze-out condition with explicit hydrodynamic calculations for the expanding hadronic phase to the daughter particles of $K^*$ mesons, we find that the larger suppression of the yield ratio of $K^*/K$ at LHC than at RHIC compared to the expectations from the statistical hadronization model based on chemical freeze-out parameters reflects the lower kinetic freeze-out temperature at LHC than at RHIC. Furthermore, we point out that for the light nuclei or hadronic molecules that are bound, the yields are affected by the freeze-out condition of the respective particle in the hadronic matter, which leads to the observation that the deuteron production yields are independent of the size of deuteron, and depend only on the number of ground state constituents.