Sequentially Charming Chemical Freeze-out in Relativistic Heavy Ion Collisions at the LHC and RHIC

In a thermally equilibrated system, hadronic yields from collisions of heavy ions serve as an anchor for determining common freeze-out parameters in the QCD phase diagram -- namely, the baryon chemical potential (μ_B) and the chemical freeze-out temperature (T_ch) -- via thermal fits in the Statistical Hadronization Model (SHM). Heavy flavor particle production is of particular interest in heavy ion phenomenology due to the large difference between the mass of bare heavy quarks and the calculated pseudocritical hadronization temperature. Due to their large masses, heavy quarks are produced in the initial hard scattering of colliding ions and then interact with other constituents in the collision fireball, potentially thermalizing. Assuming the total number of constituent heavy quarks is constant until hadronization, this thermal-like behavior of final state heavy flavor hadron yields allows for their production to be modeled by the SHM using an additional fugacity parameter. In this contribution, we show recent thermal fits to single charm hadrons measured in ALICE Pb+Pb Collisions at √s_NN = 5.02 TeV and STAR Au+Au Collisions at √s_NN = 200 GeV -- showing evidence of a flavour-dependent chemical freeze-out of light, strange and charmed hadrons in the crossover region of the QCD phase diagram. Additionally, we show thermal model predictions of heavy quarkonia, and beauty and multi-charm hadron yields as a function of √s_NN .