Results on Jets for HLT Studies by the JetMET Physics Group

1
Results on Jetsfor HLT Studies by the Jet/MET
Physics Group

• Shuichi Kunori
• Silvia Arcelli
• U. of Maryland
• 21-July-2000

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HLT Jets Algorithm

• L2
• Improve Et resolution and Et scale
• improved jet axis with finer granularity (1x1
  instead of 4x4 towers)
• LSB L1(Et0.51.0GeV) -gt L2(Et0.2GeV)
• energy calibration (non-linearity, pile-up
  energy)
• Reduce low Et fake jets due to min-bias pile-up
• jet shape
• smaller window size
• Combine with leptons and MET
• cuts on correlation, e.g. delta-eta, delta-phi...
• L3
• b-tagging

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QCD Jet Rates

• Very High rate!
• 1 kHz acceptable L1 rate for jets
• 1 jet 165 GeV
• 2 jets 120 GeV
• 3 jets 75 GeV
• 4 jets 55GeV
• Trigger Output (max)
• L1 75 kHz
• (3 kHz for Jets)
• L2 1 kHz
• L3 100 Hz (to tape)
• How to stay below 100 Hz ?
• Guideline 20Hz for Jets, MET, combination.

(S.Dasu)
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L1 Single Jet Rates
Shown on Nov.499
- Threshold _at_ 1KHz old 4x4 340GeV
12x12 250GeV
1 kHz
12x12 for high Et jet OK!
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Low Et Physics
Low Et Jets others (by V.Gavrilov)
Et (jet) Threshold 25 GeV
Need estimation of physics rates.
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qqH(135)
Need to study both!
and also to cover decay modes as many as possible!
Possible L1 e(22) 1 jet(90?) e(22) 3
jets (30)
qqH (135GeV) -gt tau -gt e/mu X -gt tau
-gt jet X
gtgt Study done by S.Lehti(HIP),S.Ilyin(MSU),
A.Nikitenko(HIP) ltlt
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Eta Coverage
(A.Nikitenko)
gt Need to cover both HE and HF region.
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1 lepton 3 jets
gtLepton (gt15GeV)
gt 3 jets (gt30GeV)
(A.Nikitenko)
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Low Et Jets and Pile-up
Reco with pile-up
Reco w/o pile-up
Generated
(Rlt0.7)
ORCA3 in-time pile-up only (no Et correction)
Fake jets lt 40GeV
(A.Krokhotine)
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ECALHCALNon-linear response
ORCA3 3GeV Pions
96 H2 Test Baem Data single pion
eta
1.5
3.0
5.0
0
0
100
200
300 (GeV)
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Jet Energy Correction
ORCA3
Et-eta dependent correction for QCD jets
E(corr) a0 a1 Et(obs)
no pile-up
In-time pile-up
Corrected scale flat within 1 - 3
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Jets ResolutionBefore/after energy correction
(ORCA3)
(Average over eta range lt 3.0)
No pile-up
In-time pile-up
3-8 improvement!
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Jet Energy Correction(no pile-up)
ORCA4
L1
L2
Corrected scale flat within a few percent.
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Jet Energy Correction(full pile-up)
L2
L1
same as no pile-up case
weak eta dependence
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Jets Resolution(before/after correction)
L1
L2
Improvement
Not much improvement!
(Correction) ( linearity) (pile-up energy) Can
we improve, if we separate those two?
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L2 Jets Rateswithout Et correction
First rate calculation, lt 24 hours old.
By S.Abdoulline
In progress L1/L2 rates at 95 point. Then
Et corrected.
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Conclusion

• We are trying to improve Jet energy resolution at
  L1/L2 in order to ger sharper turn-on in
  efficiency curves.
• We have created first version of a set of eta-Et
  dependent correction functions for L1/ L2 jets.
• We will apply the corrections to L1/L2 and
  calculate rates.
• We continue to look for improvement of Et
  correction.
• Other activities in progress
• Suppression of fake jets using smaller
  window/cone and shape cuts. (see next talk).
• Improvement of pile-up energy subtraction.
• Use of j-j, j-met, j-l correlation at L1/L2
• Beyond use of tracker(pixel) ..