First results on the NA60 pixel telescope in In-In collisions

The NA60 experiment aims at studying the production of prompt dimuons and of open charm with proton and heavy ion beams at the CERN SPS. Downstream of the nuclear targets and inside a 2.5 T dipole magnet a pixel telescope measures all charged tracks, from which some are then matched to muons recorded in the muon spectrometer placed behind a hadron absorber. The high multiplicity of charged particles imposes the use of pixel detectors. The constructed pixel telescope is composed of 16 planes with 96 pixel assemblies in total, made from radiation tolerant ALICE1 LHCb pixel readout chips bonded to pixel sensors. The 8 planes nearest to the target contain 4 pixel assemblies and are followed by 8 planes with 8 assemblies. First successful tests of 3 pixel planes, exposed to Pb-Pb collisions, were performed in October 2002. This paper describes the design and assembly of the complete NA60 pixel telescope and gives an overview of the first results obtained in the first weeks of In-In collisions.