The Level 1 Muon Trigger (L1MU) uses tracks found by the Level 1 Central Fiber Tracker Trigger (L1CFT), scintillator hits in the muon detectors, and wire hits in the muon detectors to form user-defined specific triggers that are sent to the Trigger Framework (TF). The TF subsequently uses L1MU specific triggers to form global L1 triggers for the experiment.The trigger information flow in the L1MU system is:
The main weapons in reducing the L1 trigger rate come from matching muon detector hits to L1CFT tracks, imposing a timing window to define scintillator hits, and forming centroids from wire detector hits in different planes.
There are two types of triggers formed for each octant that we call MTC05 and MTC10 for historical reasons. MTC05 triggers match tracks from the L1CFT to corresponding scintillator hits in muon detector. The L1CFT tracks include PT and sign information. The scintillator hits are defined by having their times satisfying a modest time window (sigma = 20ns) about the expected time for a prompt muon from collisions. Scintillator hits can come from one layer or as correlations of hits between layers. MTC10 triggers match centroids (stubs) formed from hits in the muon wire detectors with hits in the scintillator counters. Centroids can come from a single layer or as correlations of centroids between layers. MTC05 triggers are primarily triggers in phi and MTC10 triggers are primarily triggers in eta. Both can be used to define a good octant trigger.
L1MU triggers can be user-defined using PT (four thresholds), region (|eta| < 1.0, 1.5, or 2.0), wire and scintillator quality (none, loose, or tight), and (for dimuons) sign (same, opposite, or either). Loose triggers presently use a logical or of layers. Tight triggers presently use a logical or of correlations between pairs of layers.