update: high energy photon pairs search for rs-1 gravitons
DESCRIPTION
Vladimir Litvin, Toyoko Orimoto Caltech QCD Meeting 11 December 2007. Update: High energy photon pairs Search for RS-1 Gravitons. Introduction. Feasiblity study for RS-1 G* Relevance to QCD group: QCD backgrounds are amongst our largest. MC Samples: - PowerPoint PPT PresentationTRANSCRIPT
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Update: High energy photon pairsSearch for RS-1 Gravitons
Vladimir Litvin, Toyoko OrimotoCaltech
QCD Meeting11 December 2007
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Introduction
• Feasiblity study for RS-1 G*• Relevance to QCD group:• QCD backgrounds are amongst our largest
• MC Samples: • Produced privately at Caltech & Fermilab (no pileup)
• CMSSW_1_6_7
• Signal RS-1 G:
• MG=750, 1250, 1000, & 1500 GeV (with c = 0.1 & 0.01)
• Main Backgrounds:
• Irreducible qqbar & gg (Born & Box)
• Gamma+jets (Brem), in which one photon comes from the hard interaction, and the second comes from FSR from an outgoing quark OR the decay of a neutral hadron
• QCD jets: where we get photons from the decay of neutral hadrons
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MC Samples
Signal Samples
Background Samples
• Box and Born produced with CKIN(3)=200 (low limit of the invariant mass of the two outgoing photons, with high end is set to infinity).
• Filters were used when producing Brem and QCD samples, with selection rates 1:80 and 1:1200, respectively.
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HLT EG Efficiency
• e- related HLT paths
• HLT1EMHighEt: 1 SC with pt>80 GeV and loose isolation:
ECAL isol: < 5 GeV in R<0.3 + H/E: <5% , HCAL isol + <8 GeV in 0.15<R<0.3 + tracker iso: <4 tracks in R<0.3
• HLT1EMVeryHighEt: 1 Super-Cluster (SC) with pt>200 GeV
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Selection: Invariant Mass
Only requirement here: photon SC pt > 100 GeV… “final” cut is a 3window around MG
750=15
1000=19
1250=22
1500=28
Born Box Brem QCD
Signal Samples
Background Samples
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Selection: photon pt
Red = All candidates
Blue = MC Truth required
750 1000 1250 1500
750 1000 1250 1500
Born Box Brem QCD
Higher pt photon
Lower pt photon
Born Box Brem QCD
Each photon candidate is identified as a SC in ECAL. We require:
SC pt > 100 GeV
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Selection: ECAL Isolation
Red = All candidates
Blue = MC Truth required
750 1000 1250 1500
750 1000 1250 1500
Born Box Brem QCD
Born Box Brem QCD
Higher pt photon
Lower pt photon
ECAL Iso = ET within cone of R < 0.5
ECAL Iso < 2%
Plotted here are the Log of Ecal Iso
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Selection: H/E
Red = All candidates
Blue = MC Truth required
750 1000 1250 1500
Born Box Brem QCD
Higher pt photon
Lower pt photon
750 1000 1250 1500
Born Box Brem QCD
H/E = E of HCAL RecHits within cone of R < 0.3 / ET of SC
H/E < 5%
Plotted here are the Log of H/E
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Selection: Tracker Isolation, nTracks
Red = All candidates
Blue = MC Truth required
750 1000 1250 1500
Born Box Brem QCD
Higher pt photon
Lower pt photon
750 1000 1250 1500
Born Box Brem QCD
Tracker Isolation = number of tracks within cone of R < 0.3
nTracks <= 3
Plotted here are the Log of nTracks
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Selection: Tracker Isolation, pt Tracks
Red = All candidates
Blue = MC Truth required
750 1000 1250 1500
Born Box Brem QCD
Higher pt photon
Lower pt photon
750 1000 1250 1500
Born Box Brem QCD
Tracker Isolation = pT of tracks within cone of R < 0.3 / pT of SC
pT of tracks / SC pT< 1%
Plotted here is the Log of this variable.
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“Final” Selection Rates
• Selection rates after applying cascade of afore-mentioned cuts (%)
• With HLT1EMHighEt requirement
• Signal efficiencies ~40-50%, low (all <0.2%) background effiiency
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“Final” Selection Rates
• Selection rates after applying cascade of afore-mentioned cuts (%)
• With HLT1EMVeryHighEt requirement
• Signal efficiencies ~40-50%, low (all <0.2%) background effiiency
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Mass Distributions After Selection
750 1000 1250 1500
Born Box Brem QCD
• Numbers of events scaled to 1 fb-1
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Next Steps
• Analysis:• Finalizing analysis and working on note based on MC studies
• Systematic Errors
• Comparison with ORCA results
• Currently, this is a simple MC analysis but we will eventually develop a more robust strategy for dealing with real data
• Production:• 167: have produced signal with c=0.01, will include next
• 171: produced a couple samples before realizing huge memory usage in this release.. Noticed some large differences in efficiencies and selection variable distributions..
• 172: just produced a few samples, currently checking
• Working on gamma+jets and 2gamma+jets Alpgen or CompHEP samples to better emulate backgrounds
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Backup Slides
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Comparison of HLT EG in 167 vs 171
• E-gamma HLT path efficiencies
167 171
Appears that EG efficiencies in HLT have changed significantly from 167 to 171
167 171Born Box
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167 vs 171 Selection: photon pt
Red = 167
Blue = 171
Born bkg Box bkg
Higher Et photon
Lower Et photon
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167 vs 171 Selection: ECAL Iso
Red = 167
Blue = 171
Born bkg Box bkg
Higher Et photon
Lower Et photon
Strange peaks
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167 vs 171 Selection: H/E
Red = 167
Blue = 171
Born bkg Box bkg
Higher Et photon
Lower Et photon
More narrow H/E distributions
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167 vs 171 Selection: Tracker Isolation (pt_tracks)
Red = 167
Blue = 171
Born bkg Box bkg
Higher Et photon
Lower Et photon
Significant change in tracker isolation distributions
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167 vs 171 Selection: Tracker Isolation (N_tracks)
Red = 167
Blue = 171
Born bkg Box bkg
Higher Et photon
Lower Et photon
Decrease in tracking
efficiency?