Predictions for the heavy-ion programme at the Large Hadron Collider

TL;DR

This paper reviews predictions for the heavy-ion collision experiments at the LHC, comparing past data from SPS and RHIC with new expectations for medium properties, soft and hard probes, and potential discoveries.

Contribution

It provides a comprehensive overview of qualitative and quantitative predictions for the LHC heavy-ion program, including medium characterization and calibrated probes, and discusses future measurement potentials.

Findings

Predictions for particle multiplicities and flow at LHC

Expected signals from jets, heavy quarks, and electromagnetic probes

Potential to confirm or challenge existing medium models

Abstract

I review the main predictions for the heavy-ion programme at the Large Hadron Collider (LHC) at CERN, as available in early April 2009. I begin by remembering the standard claims made in view of the experimental data measured at the Super Proton Synchrotron (SPS) at CERN and at the Relativistic Heavy Ion Collider (RHIC) at the BNL. These claims will be used for later discussion of the new opportunities at the LHC. Next I review the generic, qualitative expectations for the LHC. Then I turn to quantitative predictions: First I analyze observables which characterize directly the medium produced in the collisions - bulk observables or soft probes -: multiplicities, collective flow, hadrochemistry at low transverse momentum, correlations and fluctuations. Second, I move to calibrated probes of the medium i.e. typically those whose expectation in the absence of any medium can be described in Quantum Chromodynamics (QCD) using perturbative techniques (pQCD), usually called hard probes. I discuss particle production at large transverse momentum and jets, heavy-quark and quarkonium production, and photons and dileptons. Finally, after a brief review of pA collisions, I end with a summary and a discussion about the potentiality of the measurements at the LHC - particularly those made during the first run - to further substantiate or, on the contrary, disproof the picture of the medium that has arisen from the confrontation between the SPS and RHIC data, and theoretical models.