Commissioning of the ATLAS High Level Muon Trigger with Beam Collisions

The ATLAS experiment is a multipurpose experiment at the Large Hadron Collider (LHC) designed to study the interactions of the fundamental particles. The interaction rate of the LHC is such that a three level trigger system is needed to select, in real time, the interesting events to be recorded by ATLAS. The LHC has recently provided the first pp collisions at $sqrt{s}=7$~TeV and the first data are used to study the performance of the ATLAS High Level muon trigger. Good performance of the algorithms is observed.