Abstract
ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-iondetector at the CERN LHC which focuses on QCD, the strong-interactionsector of the Standard Model. It is designed to address the physics ofstrongly interacting matter and the quark-gluon plasma at extreme valuesof energy density and temperature in nucleus-nucleus collisions. Besidesrunning with Pb ions, the physics programme includes collisions withlighter ions, lower energy running and dedicated proton-nucleus runs.ALICE will also take data with proton beams at the top LHC energy tocollect reference data for the heavy-ion programme and to address severalQCD topics for which ALICE is complementary to the other LHC detectors.The ALICE detector has been built by a collaboration including currentlyover 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 16 × 16 × 26 m3 with a total weight of approximately10 000 t. The experiment consists of 18 different detector systems eachwith its own specific technology choice and design constraints, drivenboth by the physics requirements and the experimental conditions expectedat LHC. The most stringent design constraint is to cope with the extremeparticle multiplicity anticipated in central Pb-Pb collisions. Thedifferent subsystems were optimized to provide high-momentumresolution as well as excellent Particle Identification (PID) over a broadrange in momentum, up to the highest multiplicities predicted for LHC.This will allow for comprehensive studies of hadrons, electrons, muons,and photons produced in the collision of heavy nuclei.Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception ofparts of the Photon Spectrometer (PHOS), Transition Radiation Detector(TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will becompleted for the high-luminosity ion run expected in 2010.This paper describes in detail the detector components asinstalled for the first data taking in the summer of 2008.
Highlights
5.1.2 Detector layout5.1.3 Signal transmission and readout5.1.4 Monitoring and calibration5.2 Photon Multiplicity Detector (PMD)
Particle identification over a large part of the phase space and for many different particles is an important design feature of ALICE with several detector systems dedicated to Particle Identification (PID): the TOF array is optimized for large acceptance and average momenta; it covers the central barrel over an area of 140 m2 with 160 000 individual cells at a radius of close to 4 m
The second category consists of requirements concerning the relative alignment of detector elements and the stability of their position during operation, typically of the order of < 50 μm for the muon system, which is monitored by optical alignment devices, and < 10 μm for the Inner Tracking System (ITS), which is ensured by a rigid carbon-fibre structure
Summary
ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong interaction sector of the Standard Model. Most detector systems will be installed and ready for data taking by mid 2008 when the LHC is scheduled to start operation, with the exception of parts of PHOS (1 out of 5 modules installed), TRD (4 out of 18), PMD, and EMCal (construction started in 2008). These detectors will be completed for the high-luminosity ion runs expected in 2010 and after
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