html5-img
1 / 21

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:

alayna
Download Presentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related