DILEPTON TRIGGER for SUSY SEARCHES @ CDF

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DILEPTON TRIGGER for SUSY SEARCHES _at_ CDF

• OUTLINE
• Motivation
• CDF Detector Trigger
• DILEPTON trigger
• layout - strategy
• monitoring - calibration
• Summary

• Melisa Rossi - Udine University
• APS April Meeting
• Tampa, Florida
• April 19th, 2005

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Motivation

• Multi-lepton signatures
• emerging from SUSY channels
• appealing for many other hep searches
• leptons from chain decays
• relatively low pT (lt 20 GeV/c)
• very clean
• particularly powerful _at_ hadron colliders where
  QCD background dominates

• Predicted cross-section SMALL!!
• s(SUSY) pb while s(pp) 50 mb

_
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CDF Detector Trigger

• Multipurpose detector
• Good calorimeter and muon coverage
• Electrons ? lt 3.6
• Muons ? lt1.5 (trigger lt 0.1 )
• Precision tracking (Silicon)
• Trigger System
• 3-level architecture
• to minimize deadtime
• path unique combination of L1,L2,L3
• Muon/Electron _at_ trigger level
• Muon 2D track matched to stub
• stub set of hits in muon chamber
• Electron 2D track matched to Em deposition in
  calorimeter

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DILEPTON trigger

• inclusive low pT lepton trigger not feasible,
  then
• DILEPTON trigger (electrons and muons)
• highly redundant (20 trigger paths)
• maximize acceptance (geometry and inefficiency)
• easier to understand trigger
• comparisons between paths
• keep calibration and monitoring samples in the
  same data set
• extraction of unbiased lepton samples
• detector conditions naturally folded in

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DILEPTON trigger strategy
MUONS
ELECTRONS
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DILEPTON trigger layout
20 trigger paths
A B C
L1 L2 2 Low-pT leptons Medium-pT leptontrack High-pT inclusive lepton
L3 2 Low-pt leptons 2 Low-pt leptons 2 Low-pt leptons

• CEM4_CMU4
• CEM4_CMUP4
• CEM4_CMX4
• CEM4_PEM8
• ......
• ..........
• CEM4_CMU4_L2_CEM8_TRK8
• .......
• CEM4_CEM4_L2_CEM12

A
B

1. baseline - workhorse
2. to recover stub/cluster inefficiency
3. to increase the acceptance

C
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DILEPTON trigger strategy
CEM4
CEM8
PEM8
CMU4
CMUP4
CMX4

• single lepton types definitions
• do not depend on the specific path
• trigger studies for each lepton type
• combine single lepton type results into trigger
  paths

Monitoring Calibration for each lepton type
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Monitoring Stability

• defining a suitable variable
• sort of purity
• (event quality information)
• expected to be stable in time
• provides information
• for each lepton type
• different estimations
• for each lepton type
• provide cross checks between paths

steps in distributions indicatives of trigger
changes
e.g. track direction used to calculate
ET (instead of cluster)
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Calibration L1 Electron Primitives

• Trigger requirements
• L1 4 GeV Central electron
• Trigger Tower
• ET 4 GeV
• Ehad/Eem 12.5
• Track
• PT 4 GeV/c
• L1 8 GeV Forward Electron
• Trigger Tower
• ET 8 GeV
• Ehad/Eem 6.25

em
em
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Calibration Probe Electrons

• Must satisfy ID cuts
• Must be unbiased for the
• trigger being calibrated
• i.e. events collected by triggers
• unrelated to the one tested
• Must come from a conversion
• each electron associated
• with a track requiring
• ?cot?lt0.15 , Sxylt0.1
• Consider 2 sub-samples
• Peak ?cot?lt0.03
• (ElectronsFakes)
• Sideband ?cot?gt0.05
• (assuming Fakes only)

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Calibration L1 Trigger Efficiency
CENTRAL
FORWARD

• Forward electron efficiency
• slow turn-on due to online-offline
• energy difference
• Central electron efficiency
• plateau value 90 due to tight
• track requirement

FORWARD
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Summary

• Motivation
• Targeting processes yielding to multiple leptons
  in final states
• DILEPTON trigger _at_ CDF
• redundant multipath trigger structure
• fully efficient beyond 4 GeV
• Strategy
• use single lepton type definition
• simplify monitoring and calibration of multipath
  trigger !!
• re-combine single lepton results into trigger
  paths
• Calibration is on-going

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Back-up TRIGGER PATH LIST

• cem4_cmu4
• cem4_cmu4_l2_cem8_pt8_ces2__trk8
• cem4_cmu4_l2_trk8_l1_cmup6_pt4
• cem4_cmup4
• cem4_cmx4
• cem4_cmx4_l2_cem8_pt8_ces2__trk8
• cem4_pem8
• cem4_pem8_l2_cem12_pt8
• cem8_pem8
• cmu4_pem8 _
• cmu4_pem8_l2_trk8_l1_cmup6_pt4
• cmup4_pem8
• cmx4_pem8
• dielectron_central_4
• dielectron_central_4_l2_cem12_pt8
• dielectron_central_4_l2_cem8_pt8_ces2__trk8
• dimuon_cmu4_cmx4
• dimuon_cmu4_cmx4_l2_trk8_l1_cmup6_pt4
• dimuon_cmucmu4

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Back-up Plug Conversion Selection