1. L3 Muon Trigger at D0 Status Report Thomas Hebbeker for Martin Wegner, RWTH Aachen, April 2002 The D0 muon system Functionality of the L3 muon trigger Muon efficiencies Muon rejection Summary and Outlook

2. The D0 Muon system  Central region (|  |  1):  3 layers of drift tubes  1 layer inside, 2 layers outside the toroid  2 layers of scintillation counters  Forward region (1<|  |<2)  3 layers of Iarocci tubes  3 layers of trigger scintillators

3. Functionality of the L3 trigger Linux PC farm, adapted offline reconstruction code, 45 ms per event M. G. M.W.

4. Input parameters "Tight" # of scint. hits in A >0 # of wire hits in A >1 # of scint. hits in BC >0 # of wire hits in BC >2  2 of track >0 (i.e. fit converged) "Loose" 1 of the "tight" criteria failed no  2 requirement "A-stub" # of scint. hits in A >0 # of wire hits in A >1 Definitions of muon categories  track quality (below)  transverse momentum  detector region  match with central track or calorimeter

5. A first glimpse: geometrical coverage On a large scale loose tracks are uniformly distributed in  and  Tracks are missing: at octant boundaries in forward region in the bottom octants at transition from WAMUS to FAMUS Number of loose tracks Single  MC,  flat from -2.5 to 2.5, p t flat from 2.5 to 200 GeV all loose tracks

6. Efficiencies for single muon MC Overall efficiencies: 50% for "tight." 77% for "loose.“ 71% for "a-stubs." Eff. for tight muons and A- stubs are correlated.

7. Data: the "Moriond samples" Sample of 1894 selected Di-Muon events in FAMUS  I n 84 % of the events at least one a-stub was found by the trigger  " 82 % " " " at least two a-stubs were found  " 83 % " " " at least one loose muons were found  " 81 % " " " at least two loose muons were found  " 78 % " " " at least one tight muon was found  " 46 % " " " at least two tight muons were found

8. Rejection factors over L1  Data: special run with L1 trigger “mu1ptxctxx” only  19324 events  Without p t cut the rejection factor is 1.88 for loose and 4.1 for tight muon tracks

9. The next steps  Fix memory leak.  Event by event comparison of L3 results and offline reconstruction.  Improve efficiency. Problem in unpacker ?  Implement cross-octant segments etc.  Build relational filters for physics. Summary current status  L3 muon trigger works “in principle”  Efficiencies too low