Impact of Service and Access Holes on the ATLAS Muon Spectrometer Performances

In this note are assessed the consequences of large, permanent service and access holes in the layout of the ATLAS muon spectrometer. The impact on global performances, such as transverse momentum resolution on individual muons and resolution on invariant mass reconstruction in a few selected physics channels with different topologies, have been investigated. The full complement of holes will accounts for a loss of 7% of events in the Higgs to four muons channel. Impacts on the geometrical acceptance of the trigger system are also discussed.