Vladimir litvin toyoko orimoto caltech qcd meeting 11 december 2007
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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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Vladimir litvin toyoko orimoto caltech qcd meeting 11 december 2007

Vladimir Litvin, Toyoko Orimoto

Caltech

QCD Meeting

11 December 2007

Update: High energy photon pairsSearch for RS-1 Gravitons


Introduction

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


Mc samples

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.


Hlt eg efficiency

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


Selection invariant mass

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


Selection photon pt

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


Selection ecal isolation

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


Selection h e

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


Selection tracker isolation ntracks

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


Selection tracker isolation pt tracks

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


Final selection rates

“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


Final selection rates1

“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


Mass distributions after selection

Mass Distributions After Selection

750

1250

1500

1000

Box

QCD

Born

Brem

  • Numbers of events scaled to 1 fb-1


Next steps

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


Backup slides

Backup Slides


Comparison of hlt eg in 167 vs 171

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


167 vs 171 selection photon pt

167 vs 171 Selection: photon pt

Red = 167

Blue = 171

Born bkg

Box bkg

Higher Et photon

Lower Et photon


167 vs 171 selection ecal iso

167 vs 171 Selection: ECAL Iso

Red = 167

Blue = 171

Born bkg

Box bkg

Strange peaks

Higher Et photon

Lower Et photon


167 vs 171 selection h e

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


167 vs 171 selection tracker isolation pt tracks

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


167 vs 171 selection tracker isolation n tracks

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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