Energy dependent chemical potentials of light hadrons and quarks based on transverse momentum spectra and yield ratios of negative to positive particles

TL;DR

This study analyzes transverse momentum spectra and yield ratios of light hadrons and quarks in various high-energy collisions to extract energy-dependent chemical potentials, revealing a critical energy point indicating a phase transition from hadronic to quark matter.

Contribution

It introduces a method to determine energy-dependent chemical potentials from experimental spectra using a two-component Erlang distribution within a thermal model framework.

Findings

Most chemical potentials decrease with increasing collision energy.

A critical energy of 3.526 GeV marks the phase transition point.

Chemical potentials tend to zero at very high energies, indicating a shift to quark-dominant states.

Abstract

We describe the transverse momentum (or mass) spectra of $\pi^\pm$, $K^\pm$, $p$, and $\bar{p}$ produced in central gold-gold (Au-Au), central lead-lead (Pb-Pb), and inelastic proton-proton ($pp$) collisions at different collision energies range from the AGS to LHC by using a two-component (in most cases) Erlang distribution in the framework of multi-source thermal model. The fitting results are consistent with the experimental data and the energy-dependent chemical potentials of light hadrons ($\pi$, $K$, and $p$) and quarks ($u$, $d$, and $s$) in central Au-Au, central Pb-Pb, and inelastic $pp$ collisions from the yield ratios of negative to positive particles obtained from the normalization constants are then extracted. The study shows that most types of energy-dependent chemical potentials decrease with increase of collision energy over a range from the AGS to LHC. The curves of all types of energy-dependent chemical potentials, obtained from the linear fits of yield ratios vs energy, have inflection points at the same energy of 3.526 GeV, which is regarded as the critical energy of phase transition from a hadron liquid-like state to a quark gas-like state in the collision system and indicates that the hadronic interactions play an important role in this period. At the RHIC and LHC, all types of chemical potentials become small and tend to zero at very high energy, which confirms that the collision system possibly changes completely from the hadron-dominant liquid-like state to the quark-dominant gas-like state and the partonic interactions possibly play a dominant role at the LHC.