Hagedorn's Hadron Mass Spectrum and the Onset of Deconfinement

TL;DR

This paper reviews the historical development of the concept of the Hagedorn temperature and its relation to the onset of quark-gluon plasma formation in high-energy nucleus-nucleus collisions.

Contribution

It discusses the connection between Hagedorn's hypothesis of a limiting hadronic temperature and the experimental evidence for deconfinement onset at CERN SPS energies.

Findings

Confirmation of the Hagedorn temperature as the phase transition point.

Observation of the onset of deconfinement in lead-lead collisions.

Historical overview of hadron mass spectrum measurements.

Abstract

A brief history of the observation of the onset of deconfinement - the beginning of the creation of quark gluon plasma in nucleus-nucleus collisions with increasing collision energy - is presented. It starts with the measurement of hadron mass spectrum and the Hagedorn's hypothesis of the limiting temperature of hadronic matter (the Hagedorn temperature). Then the conjecture that the Hagedorn temperature is the phase transition temperature was formulated with the crucial Hagedorn participation. It was confirmed by the observation of the onset of deconfinement in lead-lead collisions at the CERN SPS energies.