Study of the CPC tracking chambers for the Alice dimuon spectrometer

ALICE (A Large Ion Collider Experiment) is the only detector dedicated to the study of nucleus-nucleus interactions at the LHC. It will investigate the physics of strongly interacting matter at extreme energy densities, where the formation of a new phase of matter, the quark-gluon plasma (QGP), is expected. ALICE is composed of many sub-detectors. Among of them, the forward muon spectrometer which include absorbers, dipole magnet, ten tracking chambers and four trigger chambers. The main purpose of the forward muon arm is to measure the complete spectrum of heavy quark vector mesons J/ψ,ψ',υ,υ',υ'' via their muonic decay (μ+μ-) in heavy-ion collisions. The melting of these resonances is one of the most promising signatures of QGP formation. Related to the design of this detector at SUBATECH, the development of the tracking chamber (CPC) has been carried out. In-beam tests were led at CERN. The goal of these tests was to validate the operation of Cathode Pad Chamber in term of spatial resolution and reconstruction efficiency. A full simulation of chamber response using Monte-Carlo method was done. The goal was both, to reproduce experimental data, and to introduce the track angle effect into the simulation code of ALICE experiment (AliRoot). As expected, inclined tracks deteriorate the momentum estimation, and consequently, deteriorate the invariant mass resolution of resonances. (author)