A critical review of RHIC experimental results

TL;DR

This review critically examines RHIC experimental results, evaluating evidence for the formation of a strongly-coupled quark-gluon plasma and discussing alternative interpretations of the data.

Contribution

It provides a comprehensive analysis of RHIC data, questioning the prevailing interpretation of a perfect liquid QGP and exploring alternative explanations.

Findings

Evidence for strongly-coupled QGP is debated.

Two-component model offers an alternative to QGP interpretation.

Some experimental results may support different collision mechanisms.

Abstract

The relativistic heavy ion collider (RHIC) was constructed to achieve an asymptotic state of nuclear matter in heavy ion collisions, a near-ideal gas of deconfined quarks and gluons denoted quark-gluon plasma or QGP. RHIC collisions are indeed very different from the hadronic processes observed at the Bevalac and AGS, but high-energy elementary-collision mechanisms are also non-hadronic. The two-component model (TCM) combines measured properties of elementary collisions with the Glauber eikonal model to provide an alternative asymptotic limit for A-A collisions. RHIC data have been interpreted to indicate formation of a {\em strongly-coupled} QGP or "perfect liquid". In this review I consider the experimental evidence that seems to support such conclusions and alternative evidence that may conflict with those conclusions and suggest different interpretations.