Phenomenology of strangeness production at high energies

Abstract

The strange-quark occupation factor ($\gamma_s$) is determined from the statistical fit of the multiplicity ratio $\mathrm{K}^+/\pi^+$ in a wide range of nucleon-nucleon center-of-mass energies ($\sqrt{s_{NN}}$). From this single-strange-quark-subsystem, $\gamma_s(\sqrt{s_{NN}})$ was parametrized as a damped trigonometric functionality and successfully implemented to the hadron resonance gas model, at chemical semi-equilibrium. Various particle ratios including $\mathrm{K}^-/\pi^-$, $\mathrm{\Lambda}/\pi^-$, and $\mathrm{\bar{\Lambda}}/\pi^-$ are well reproduced. The phenomenology of $\gamma_s(\sqrt{s_{NN}})$ suggests that, the hadrons ($\gamma_s$ raises) at $\sqrt{s_{NN}} \simeq 7~$GeV seems to undergo a phase transition to a mixed phase ($\gamma_s$ declines), which is then derived into partons ($\gamma_s$ remains unchanged with increasing $\sqrt{s_{NN}}$), at $\sqrt{s_{NN}} \simeq 20~$GeV.