Description and Optimisation of the ALICE dimuon trigger

The main considerations about the ALICE dimuon trigger can be found in the Addendum to the ALICE Technical Proposal (T.P. in this note), concerning the forward muon spectrometer. The main task of the trigger is to select the dimuon signals, mainly from J/Psi and Upsilon resonances, amongst the huge background of muons from pions, kaons, charm decays and soft background in order to keep the acquisition rates at a satisfactory level. This is achieved with a cut on the muon transverse momentum performed by the trigger electronics and processors. A dimuon mass cut can also be done (not treated in this note). <P> This note presents a detailed simulation which goal is to optimize the dimuon trigger. It includes the description of the set-up geometry and segmentation as well as the trigger electronics functions. Many improvements are suggested by the results of this simulation, as compared to the T.P. An update of the trigger rates and efficiency is given. <P> Even though we describe the main elements of the dimuon trigger in order to explain the simulation process, the reader has to be aware that this is clearly not a technical document.