Hadron Production in Ultra-relativistic Nuclear Collisions: Quarkyonic Matter and a Triple Point in the Phase Diagram of QCD

TL;DR

This paper proposes that hadron production in ultra-relativistic nuclear collisions can be explained by three distinct phases of matter—Hadronic, Quarkyonic, and Quark-Gluon Plasma—meeting at a triple point in the QCD phase diagram, accounting for observed particle ratios.

Contribution

It introduces the concept of a triple point in the QCD phase diagram involving three matter phases, explaining features of hadron production at CERN-SPS energies.

Findings

Identification of three phases of matter in QCD

Explanation of non-monotonic strange particle ratios

Proposal of a triple point in the phase diagram

Abstract

We argue that features of hadron production in relativistic nuclear collisions, mainly at CERN-SPS energies, may be explained by the existence of three forms of matter: Hadronic Matter, Quarkyonic Matter, and a Quark-Gluon Plasma. We suggest that these meet at a triple point in the QCD phase diagram. Some of the features explained, both qualitatively and semi-quantitatively, include the curve for the decoupling of chemical equilibrium, along with the non-monotonic behavior of strange particle multiplicity ratios at center of mass energies near 10 GeV. If the transition(s) between the three phases are merely crossover(s), the triple point is only approximate.