Commissioning and Performance of the LHCb HLT1 muon trigger

The initial proton-proton collision at $\sqrt{s}$=0.9~TeV in 2009 and $\sqrt{s}$=7~TeV in 2010 allowed to commission the LHCb HLT1 muon trigger. In this note we describe the changes in the HLT1 muon reconstruction introduced to deal with real Data and the detailed comparison of the variables used in the HLT1 muon triggers with simulation. The measured rate retention is not far from the expected values. We also give an initial estimation of the trigger efficiency on selected $J\psi\mu\mu$ events and extrapolate this efficiency to the phase space of the $B_s\mu\mu$ decay.