ALICE technical design report: Detector for high momentum PID

ALICE (A Large Ion Collider Experiment) is an experiment at the Large Hadron Collider (LHC) optimized for the study of heavy-ion collisions, at a centre of mass energy ∼ 5.5 TeV. The prime aim of the experiment is to study in detail the behaviour of matter at high densities and temperatures, in view of probing deconfinement and chiral symmetry restoration. The detector consists essentially of two main components: the central part, composed of detectors mainly devoted to the study of hadronic signals and dielectrons in the pseudorapidity range −1 <η< 1, and the forward muon spectrometer, devoted to the study of quarkonia behaviour in dense matter. The layout of the ALICE set-up is shown in colour Fig. 1.i. The first technical challenge is imposed by the large number of particles created in the collisions of lead ions. There is a considerable spread in the presently available predictions for the multiplicity of charged particles produced in a central Pb–Pb collision. The design of the experiment has been based on the highest value, 8000 charged particles per unit of rapidity, at mid rapidity. This multiplicity dictates the granularity of the detectors and their optimal distance from the colliding beams. The detailed characterization of ion–ion collisions requires particles to be measured and identified over a large range of momenta and masses. This second challenge has determined the rather complex particle identification scheme of ALICE.