Physics Priorities for Trigger Development

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Physics Priorities for Trigger Development

• Leonard Apanasevich (UIC)
• Pedrame Bargessa (Rice)

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Outline

• Introduction to the Trigger Development Group
• Physics priorities during the initial
  commissioning stage
• Initial trigger menu planning
• Start-up Min-Bias Trigger Suite
• Evolution of the Trigger Menu

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Trigger Development Group (i)
Ideas for new triggers come in from PAGs, POGs,
DPGs, trigger community.
For each new trigger
Ensure the resultant global menu fits within
the constraints of the L1 and HLT systems. If
necessary fine tune thresholds and prescales
Provide the tools and expertise to incorporate
new trigger paths in the menu
Evaluate efficiencies and CPU performance for
various luminosity and pileup scenarios
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Trigger Development Group (ii)
Immediate priority

• Provide trigger menus for luminosity/pileup
  scenarios envisioned during the initial startup
  stage of the LHC
• Develop infrastructure needed to allow flexible
  and rapid development of trigger menus while
  simultaneously keeping an eye on
• Rates, Efficiencies, and CPU performance

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Physics Priorities for Phase A

• Calibrate and align the detector understand the
  trigger system
• Minbias PT and Rapidity Distributions
• Jet, J/?, ?, etc. triggers
• Establish MET
• Gamma Jet Calibration
• Begin to re-establish the Standard Model
• Study Jet Angular Distribution, Dijets
• Look at standard candles W, Z, top

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LHC Startup Stages
Mike Lamont, 20.06.07
Bunches ? Ib Luminosity Event rate
1 x 1 18 1010 1027 Low
43 x 43 18 3 x 1010 3.8 x 1029 0.05
43 x 43 4 3 x 1010 1.7 x 1030 0.21
43 x 43 2 4 x 1010 6.1 x 1030 0.76
156 x 156 4 4 x 1010 1.1 x 1031 0.38
156 x 156 4 9 x 1010 5.6 x1031 1.9
156 x 156 2 9 x 1010 1.1 x1032 3.9
Stage A Summary
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Simulated L1 rates at 1028
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Initial Trigger Menu
Level-1 Trigger Totally Open _at_ 12.5 kHz

• Need HLT early on to reduce Level-1 output rate
  to 200 Hz to tape

• Suite of min-bias triggers
• Calorimeter low ?ET or any muon (no PT cut)
• Calorimeter low ET Electron (? 5 GeV) or Jet (?
  10 GeV)
• Any muon (effectively ? 3 GeV PT cut)
• Other candidate triggers for later running are
  active for diagnostic and study purposes

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MinBias Trigger Suite

• Prescaled events in crossings and gaps
• Minimum total calorimeter Etmin gt Enoise
• Single-tower triggers
• Low threshold L1 "jet" trigger (10 GeV Et)
• Separate forward jets threshold for HF trigger as
  well (Etmin(HF) gt Enoise)
• Low threshold Electron trigger (no isolation
  requirements)
• HF ET rings (calculated in GCT from RCT sums).
• Tower over threshold bits in HB/HE/HF
• Total ET seen in the detector -- this is part of
  the regular trigger
• Low threshold Jet trigger also part of the
  regular trigger
• Dedicated scintillators in the forward region
  (aka OPAL scintillators) -- limited acceptance
  but used as a check
• TOTEM detectors if available

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Evolution of the Trigger Menu
Employ simultaneous strategies as luminosity
rates rise

• Keep low threshold triggers by adding conditions
  and/or prescales
• Electrons add isolation at lower thresholds, H/E
• Jets change prescales/add ?-bits to preserve
  thresholds for ?s.
• Muons add quality conditions at lower thresholds
• more hits on muon tracks of individual muon
  trigger systems
• require coincidence between RPC and either DT or
  CSC
• add isolation at lower thresholds
• Raise thresholds for unrestricted triggers
• Above lowest possible thresholds do not impose
  conditions
• Calorimeter no isolation above higher threshold
  or ?-bits
• Muon remove coincidence isolation, relax hit
  requirement
• L1 conditions first validated in HLT, then
  migrated

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Conclusions

• The Trigger Development Group has been formed and
  is working on preparing trigger menus for the
  initial commissioning stage of the LHC
• Strategies for trigger development and evolution
  have be implemented
• We request input from all corners of the
  collaboration
• We are looking forward to the challenges that lie
  ahead in the upcoming months