Hadron yield correlation and constituent quark degree of freedom in heavy ion collisions

TL;DR

This study uses a quark combination model to analyze hadron yields in heavy ion collisions across various energies, finding constituent quark degrees of freedom are crucial above 30 AGeV but not at 20 AGeV.

Contribution

It demonstrates the energy threshold where constituent quark degrees of freedom become essential in thermal hadron production in heavy ion collisions.

Findings

Hadron yield correlations are well reproduced above 30 AGeV.

Quark combination model fails at 20 AGeV, indicating a shift in underlying physics.

Predictions made for yields at LHC energy of 5.5 TeV.

Abstract

Based on the assumption of the production of deconfined quark matter, we use a quark combination model to systematically investigate hadron yields in heavy ion collisions from RHIC $\sqrt{s_{NN}}=200, 130, 62.4$ GeV to SPS $E_{beam}=158, 80, 40, 30, 20 $ AGeV. We find that as the collision energy is greater than or equal to 30 AGeV the yields of various hadrons, their correlations, in particular, the observables $A=\frac{\bar{\Lambda} k^{-} p}{\Lambda k^{+} \bar{p}}$ and $B=\frac{\Lambda k^{-}\bar{\Xi}^{+}}{\bar{\Lambda} k^{+}\Xi^{-}}$, are all reproduced; however, as the collision energy drops to 20 AGeV quark combination fails. This indicates that the constituent quark degrees of freedom represent a decisive factor in thermal hadron production above 30 AGeV and seem to be invalid at 20 AGeV. In addition, hadron yields as well as particle ratios at midrapidity in the most central Pb+Pb collisions at $\sqrt{s_{NN}}=5.5$ TeV are predicted.