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Level 1 Trigger: Introduction

Level 1 Trigger: Introduction. Su Dong. L1 trigger objects and strategy Implementation features L1 composition and rate projection. Trigger Requirements and General Strategy. The basic requirement of the trigger system is to select Interesting physics events with high, stable and well

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Level 1 Trigger: Introduction

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  1. Level 1 Trigger: Introduction Su Dong • L1 trigger objects and strategy • Implementation features • L1 composition and rate projection Caltech Trigger/DAQ/Online workshop

  2. Trigger Requirements and General Strategy The basic requirement of the trigger system is to select Interesting physics events with high, stable and well understood efficiency. Some implementation features: • Trigger lines mostly defined by generic topology (2,3,4 particles etc.), not by specific physics source. • Deploy orthogonal triggers using pure DCH or pure EMC triggers with high efficiency for affordable topologies. stability and efficiency measurability. • Built in tolerance for detector inefficiencies: • Accept 3 out of 4 hits for track segment finding in a superlayer • Allow missing segments in L1 and L3 track triggers • Allow at least one signal particle is allowed to miss DCH or EMC trigger, whenever possible. Caltech Trigger/DAQ/Online workshop

  3. L1 Trigger System Caltech Trigger/DAQ/Online workshop

  4. L1 Trigger Primitives (I) • DCT primitives: BLT coarse rf tracks with no Z/tanl/Pt info • A16: long track reaching SL10 (Pt>180MeV) • B16: short track reaching SL5 (Pt>120MeV) ZPD 3D tracks with Z/tanl/Pt info reaching SL7 • Z16: standard Z track (|Z|<12cm, |Pt|>200 MeV) • Zt8:tight Z cut track (|Z|<10cm, |Pt|>200 MeV) • Z’8:high Pt track (|Z|<15cm, |Pt|>800 MeV) • Zk4:moderate Pt cut (|Z|<10cm, |Pt|>350 MeV) Caltech Trigger/DAQ/Online workshop

  5. L1 Trigger Primitives (II) • EMT primitives: • M20: f strip energy sum MIP (>120MeV) • G20: f strip energy sum medium E (>300MeV) • E20: f strip energy sum high E (>800MeV) • Y10: Backward barrel high E (>1 GeV) • IFT primitive: • U3: coded pattern number for various 2 muon and 1 muon barrel/endcap hit topologies Caltech Trigger/DAQ/Online workshop

  6. L1 Trigger Features (I) • PEP-II beam essentially continuous so that L1 trigger also operates in `DC’ mode in conjunction with fully pipelined subdetector frontend electronics. • There is no fast trigger detector element such as TOF but still get L1 time resolution of ~50ns. • Subsystem readout work on raw waveform to calculate pulse height => decouple trigger timing from pulse heights. However, there are pathological effects in frontend electronics input to trigger or vulnerable trigger settings which can introduce gross timing shifts. Careful testing is required for changes with timing consequences. Caltech Trigger/DAQ/Online workshop

  7. Ghost retriggering events (from 2000) Due to EMC electronics glitch during a ramping down pulse Caltech Trigger/DAQ/Online workshop

  8. L1 Trigger Features (II) • Low multiplicity triggers such as 1B can sometimes saturate at high background conditions so that e.g. 2B is on, but 1B may appear to be off due to lack of off->on transition. • GLT trigger lines are currently optimized for best mean time alignment between lines. If we were to deliberately delay L1 as late as possible to minimize SVT ‘background hit poisoning’, we may need to try optimizing for best late edge alignment. Caltech Trigger/DAQ/Online workshop

  9. L1 Trigger Line Naming Conventions • 3B&2Ameans B>3 and A>2 • M* means2 M hits back to back • EM* means M and E hits back to back • A+ meansA>1 & A’>1 • D2 means B>2 & A>1 (short hand 2 trk trg) • BMmeans B matched by M in sameflocation For counting distinct objects from the f maps: • Normal objects (B,A,M,E etc.) are separated by more than 1 f bin: 22.5o for DCT tracks, 18o for EMT hits. • Back to back angles cuts for B*,M*,EM* ~120o. • DCT/EMT match objects BM ~90o apart. Caltech Trigger/DAQ/Online workshop

  10. This configuration is used throughout 2001-2004 runs. The ‘Beam/beam’ contribution can also be due to low angle Bhabha debris. Feb/02 Caltech Trigger/DAQ/Online workshop

  11. L1 Trigger Efficiency 2001-2004 old DCT configuration: Pure DCTPure EMTAll L1 lines BB generic99.1% 99.8% >99.9% B->p0p0 + B->X79.7% 99.2% 99.8% B->tn+ B->X92.2% 95.5% 99.7% cc95.3% 98.8% 99.9% uds90.6% 95.6% 98.2% Bhabha98.9% 99.2% >99.9% mm 99.1% - 99.6% tt80.6% 77.6% 94.5% ( Hadronic final states: all events Leptonic final states: fiducial events) Caltech Trigger/DAQ/Online workshop

  12. L1 Rate Projection Feb/02 Background run result suggest Possible model: L1 Rate (Hz) = 125 (cosmic) + 50*ILER(A) + 190*IHER(A) + 180*I2HER(A) + 70*L/1033 + 100*ILER*IHER at good conditions Caltech Trigger/DAQ/Online workshop

  13. Checking L1 Rate Projection Derived background L1 rate compared to prediction: >2*backgr 24% >3*backgr 4.6% >4*backgr 2.2% Use prediction with caution ! Caltech Trigger/DAQ/Online workshop

  14. L1 Rate Extrapolations (Jan/04) Caltech Trigger/DAQ/Online workshop

  15. L1 Rate Extrapolations (Jan/04) Model-2: + 100*Iher*I2ler+ 100*L Caltech Trigger/DAQ/Online workshop

  16. Can we get more reduction out of DCZ ? Caltech Trigger/DAQ/Online workshop

  17. Backup Slides Caltech Trigger/DAQ/Online workshop

  18. L1 Trigger Rate Growth vs Trigger Types Caltech Trigger/DAQ/Online workshop

  19. New L1 Rate Extrapolations (II) Model-1: + 50*Iher*Iler + 120*Iher*I2ler+ 70*L Caltech Trigger/DAQ/Online workshop

  20. HER background characteristics Caltech Trigger/DAQ/Online workshop

  21. Lumi vs beam current Caltech Trigger/DAQ/Online workshop

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