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The possibility of colliding heavy nuclei with high luminosity at the Large Hadron Collider, expected to start operating in 2007 at CERN, offers a unique opportunity to investigate the behaviour of strongly interacting matter under extreme conditions of compression and heating. This will allow unprecedented tests of our understanding of equilibration processes and equilibrium states in Quantum Chromo-Dynamics (QCD), the fundamental theory of strong interactions. In particular, equilibrium QCD predicts that a phase transition to a plasma of deconfined partons, (the Quark–Gluon Plasma, or QGP), occurs at a critical energy density which is within experimental reach. Measurements at the LHC will probe extensively the properties of the bulk partonic matter produced in nucleus–nucleus collisions. The ALICE experiment—presently under construction—is the only LHC experiment designed specifically for the study of nucleus–nucleus collisions.

This special issue of Journal of Physics G: Nuclear and Particle Physics is dedicated to the publication of the second volume of the ALICE Physics Performance Report. The first volume (published as volume 30, issue 11 of the journal) contained a general introductory part on the physics of nucleus–nucleus collisions at the LHC and a description of the experimental apparatus. In this second and last volume, the expected performance of the apparatus in the main areas of research of ALICE is analysed and discussed based on a series of representative measurements that were simulated and studied in detail.

Through publication of the ALICE Physics Performance Report in Journal of Physics G, we hope to offer to the wider physics community an in-depth view of the research potential provided by this unique scientific instrument.

ALICE is a general-purpose heavy-ion experiment designed to study the physics of strongly interacting matter and the quark–gluon plasma in nucleus–nucleus collisions at the LHC. It currently involves more than 900 physicists and senior engineers, from both the nuclear and high-energy physics sectors, from over 90 institutions in about 30 countries.

The ALICE detector is designed to cope with the highest particle multiplicities above those anticipated for Pb–Pb collisions (dN_ch/dy up to 8000) and it will be operational at the start-up of the LHC. In addition to heavy systems, the ALICE Collaboration will study collisions of lower-mass ions, which are a means of varying the energy density, and protons (both pp and pA), which primarily provide reference data for the nucleus–nucleus collisions. In addition, the pp data will allow for a number of genuine pp physics studies.

The detailed design of the different detector systems has been laid down in a number of Technical Design Reports issued between mid-1998 and the end of 2004. The experiment is currently under construction and will be ready for data taking with both proton and heavy-ion beams at the start-up of the LHC.

Since the comprehensive information on detector and physics performance was last published in the ALICE Technical Proposal in 1996, the detector, as well as simulation, reconstruction and analysis software have undergone significant development. The Physics Performance Report (PPR) provides an updated and comprehensive summary of the performance of the various ALICE subsystems, including updates to the Technical Design Reports, as appropriate.

The PPR is divided into two volumes. Volume I, published in 2004 (CERN/LHCC 2003-049, ALICE Collaboration 2004 J. Phys. G: Nucl. Part. Phys.30 1517–1763), contains in four chapters a short theoretical overview and an extensive reference list concerning the physics topics of interest to ALICE, the experimental conditions at the LHC, a short summary and update of the subsystem designs, and a description of the offline framework and Monte Carlo event generators.

The present volume, Volume II, contains the majority of the information relevant to the physics performance in proton–proton, proton–nucleus, and nucleus–nucleus collisions. Following an introductory overview, Chapter 5 describes the combined detector performance and the event reconstruction procedures, based on detailed simulations of the individual subsystems. Chapter 6 describes the analysis and physics reach for a representative sample of physics observables, from global event characteristics to hard processes.