The muon L1 trigger will primarily use the central fiber tracker trigger matched to one or more elements in the muon system. The scintillator counter will provide a timing window of about 15-20 ns, while adding requirements of the wire chambers will reduce combinatorics. Additional requirements that some elements are outside the iron are included makes an effective pt cut at about 4 GeV/c in the central region. The nominal thresholds are st by the central fiber tracker and are:
The muon L2 trigger has available the complete time information, including calibration constants and PDT deltaT, for the wire and scintillator elements. It also has scintillator hits which have been read out using the wide gate in addition to those channels which passed the narrow L1 gate. Among other things it can do, it will improve on the L1 correlation between the muon scintillator and wire hits, between the A-layer and BC-layer muon segments, and between the muon segments and the central tracking. The scintillator time resolution will be better due to using calibration and time-of-flight corrections allowing better discrimination between fast, slow, and out-of-time sources. L2 should also allow better discrimination between 1 and 2 muon events, some punchthrough rejection, and an invariant mass determination (though with modest resolution).
The muon L3 trigger will utilize aspects of the offline muon reconstruction. The muon L2 will act as a L3 "pre-processor" as it will define geographic regions where L3 should unpack and track. L3 muons will have more complete information on the vertex and inner tracking components which will yield an improved momentum resolution, and the ability to require that multiple muons came from the same vertex. Fits done to the muon detector elements will be essentially the same as in the final offline reconstruction, and requirments on matching the muon track to the inner tracking can reduce any remnant combinatorics plus punchthroughs. L3 will also use the calorimeter energy to reduce combinatorics, plus also separate muons into isolated and non-isolated. L3 will improve on L2's ability to seprate muon sources into prompt, slow, or out-of-time by fitting the available scintillator hits along a track to the particle's velocity. L3 can remove remnant cosmic ray muons both by their being out-of-time and by looking for evidence of a penetrating track on the opposite side of the detector. L3 can also clean up single muon events which L1 and L2 identified as dimuons, such as those which pass through the FAMUS-WAMUS overlap region.
Last modified: May 5, 2000