GEANT Study and Optimisation of an Absorber for the Dimuon Detector in ALICE

A dimuon spectrometer is under study to complete the ALICE detector at small angles. In order to reduce the background from ¹ and K decays, an absorber has to be inserted between the target point andthe spectrometer. This absorber must also be optimized to reduce the total punchthrough probability to an acceptable level without destroying too much the dimuon mass resolution. The backscattering in the ALICE TPC due to the insertion of the absorber has to be regarded too. Finally, the shielding of the beam pipe is also correlated to this study.