Dimuon reconstruction in heavy ion collisions using a detailed description of CMS geometry

The algorithm for the reconstruction of muon pairs produced in heavy ions collisions and detected in the CMS barrel part is presented. With an efficiency of 66% for the Upsilon( 1S)-decay dimuons in the case of central Pb-Pb collisions it enhances the Signal/Background by a factor 6 in the pseudorapidity region -0.8<eta<0.8. For the 0.8<|eta|<1.5 evaluated efficiency is 45% for Upsilon into mu+mu- and 15% for uncorrelated muons from pi/K decays.