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Update: High energy photon pairs Search for RS-1 Gravitons

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:

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Update: High energy photon pairs Search for RS-1 Gravitons

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  1. Vladimir Litvin, Toyoko Orimoto Caltech QCD Meeting 11 December 2007 Update: High energy photon pairsSearch for RS-1 Gravitons

  2. 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

  3. 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.

  4. 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

  5. Selection:  Invariant Mass Signal Samples 1000 =19 750 =15 1250 =22 1500 =28 Background Samples Born Box Brem QCD Only requirement here: photon SC pt > 100 GeV… “final” cut is a 3window around MG

  6. 750 1000 1500 1250 Born Box Brem QCD 750 1000 1500 1250 Born Box Brem QCD Selection: photon pt Each photon candidate is identified as a SC in ECAL. We require: SC pt > 100 GeV Higher pt photon Lower pt photon Red = All candidates Blue = MC Truth required

  7. 750 1000 1500 1250 Born Box Brem QCD 750 1000 1500 1250 Born Box Brem QCD Selection: ECAL Isolation ECAL Iso =  ET within cone of R < 0.5 ECAL Iso < 2% Plotted here are the Log of Ecal Iso Higher pt photon Lower pt photon Red = All candidates Blue = MC Truth required

  8. 750 1000 1500 1250 Born Box Brem QCD 750 1000 1500 1250 Born Box Brem QCD Selection: H/E 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 Higher pt photon Lower pt photon Red = All candidates Blue = MC Truth required

  9. 750 750 1000 1000 1500 1500 1250 1250 Born Born Box Box QCD QCD Brem Brem Selection: Tracker Isolation, nTracks Tracker Isolation = number of tracks within cone of R < 0.3 nTracks <= 3 Plotted here are the Log of nTracks Higher pt photon Lower pt photon Red = All candidates Blue = MC Truth required

  10. 750 1000 1250 1500 750 1000 1500 1250 Born Born Box Box QCD QCD Brem Brem Selection: Tracker Isolation, pt Tracks 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. Higher pt photon Lower pt photon Red = All candidates Blue = MC Truth required

  11. “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

  12. “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

  13. Mass Distributions After Selection 750 1250 1500 1000 Box QCD Born Brem • Numbers of events scaled to 1 fb-1

  14. 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

  15. Backup Slides

  16. Comparison of HLT EG in 167 vs 171 • E-gamma HLT path efficiencies Born Box 171 171 167 167 Appears that EG efficiencies in HLT have changed significantly from 167 to 171

  17. 167 vs 171 Selection: photon pt Red = 167 Blue = 171 Born bkg Box bkg Higher Et photon Lower Et photon

  18. 167 vs 171 Selection: ECAL Iso Red = 167 Blue = 171 Born bkg Box bkg Strange peaks Higher Et photon Lower Et photon

  19. 167 vs 171 Selection: H/E Red = 167 Blue = 171 Born bkg Box bkg Higher Et photon More narrow H/E distributions Lower Et photon

  20. 167 vs 171 Selection: Tracker Isolation (pt_tracks) Red = 167 Blue = 171 Born bkg Box bkg Significant change in tracker isolation distributions Higher Et photon Lower Et photon

  21. 167 vs 171 Selection: Tracker Isolation (N_tracks) Red = 167 Blue = 171 Born bkg Box bkg Decrease in tracking efficiency? Higher Et photon Lower Et photon

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