Heavy-ion physics at the CERN SPS H2: NA35, NA49 and NA61/SHINE (with personal recollections)

TL;DR

This review summarizes 40 years of heavy-ion collision experiments at CERN SPS, highlighting key discoveries of quark-gluon plasma signals, deconfinement onset, and the phase diagram of nuclear matter.

Contribution

It provides a unified account of the NA35, NA49, and NA61/SHINE experiments, emphasizing their collective role in understanding QGP and nuclear matter transitions.

Findings

First QGP signal observed at SPS energy in S+S collisions

Evidence for deconfinement onset at low SPS energies

Established the diagram of high-energy nuclear collision regimes

Abstract

This review presents a unified account of the NA35, NA49, and NA61/SHINE experiments, which together form a continuous programme of heavy-ion studies conducted at the H2 beamline of the CERN North Area using the SPS accelerator. The programme, spanning about 40 years, was driven by the search for a high-density state of strongly interacting matter - the quark--gluon plasma (QGP) - and the transitions leading to it. The review focuses on this primary line of research. The highlights of the programme include the observation of the first signal of QGP creation at the top SPS energy in S+S collisions by NA35, evidence for the onset of deconfinement at low SPS energies by NA49, and the establishment by NA61/SHINE of the diagram of high-energy nuclear collisions, featuring transitions between hadron-, string-, and QGP-dominated regimes. This predominantly scientific review is complemented by brief personal recollections related to the discussed topics.