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g ’s and fake g ’s in CMS: Application of a Fisher Discriminate

g ’s and fake g ’s in CMS: Application of a Fisher Discriminate. Michael Anderson Kevin Flood. March 18, 2009. Today. Plots/variables of g ’s and jets leaving energy deposits similar to g ’s Results of Fisher multivariate to discriminate g ’s and g ’s faked by jets Samples used:

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g ’s and fake g ’s in CMS: Application of a Fisher Discriminate

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  1. g’s and fake g’s in CMS: Application of a Fisher Discriminate Michael Anderson Kevin Flood March 18, 2009

  2. Today • Plots/variables of g’s and jets leaving energy deposits similar to g’s • Results of Fisher multivariate to discriminate g’s and g’s faked by jets • Samples used: • Pythia-produced g+jetevents (signal) • Pythia-produced di-jet QCD events (background) • Event displays and energy-deposit pictures from cmsShow

  3. g+jet Monte Carlo • ET distribution of DR matched grec in endcappassing either: • ET>20GeV, DR<0.1, and H/E<0.2OR • Same as above, plus Loose Photon ID cuts: • Official PhotonID has significantly reduced efficiency as ET(g) increases! Scaled to 200pb-1 -grec -grec passing photonID SEcal ET in 0.06-0.4 ring < 10 GeV SHcal ET 0.1-0.4 ring < 10 GeV STrackpT in 0.04-0.4 ring < 30 GeV R9 = E3x3/E(g) > 0.8 [slide 31 lists all PhotonIDconfig parameters]

  4. g+jet Monte Carlo • ET distribution of DR matched grec in barrelpassing either: • ET>20GeV, DR<0.1, and H/E<0.2OR • Same as above, plus Loose Photon ID cuts: • Similar story in barrel – we can do better than this! Scaled to 200pb-1 -grec -grec passing photonID SEcal ET in 0.06-0.4 ring < 10 GeV SHcal ET 0.1-0.4 ring < 10 GeV STrackpT in 0.04-0.4 ring < 30 GeV R9 = E3x3/E(g) > 0.8 [slide 31 lists all PhotonIDconfig parameters]

  5. Fisher Input • Trained Fisher with 10 variables to discriminate g’s and jets faking g’s: • (SEcal in solid 0.4 cone-ET(g)) / ET(g) • (SHcal in 0.1-0.4 ring) / ET(g) • (STrackpT in solid 0.4 cone) / ET(g) • H/E • R9 = E3x3/E(g) • E2x5/E5x5 • E3x2/E5x5 • Zernike Z20 (circular) moment • E-weighted f-width • E-weighted h-width • See appendix slides 31-34 to see distributions of these Cuts on both signal and background grec before training: H/E < 0.2 # Tracks in 0.4 Cone ≤ 2 20 GeV < ET < 1000 GeV Trained Barrel & Endcap separately, Barrel: |h| < 1.45 Endcap: 1.55 < |h| < 2.50

  6. Fisher Response • In the barrel • In the endcap • Cut everything below dashed line • Statistics used:

  7. Results for fake g’s • ET distribution of the grec from dijet QCD • Original (ET>20GeV, H/E<0.2, |h|<1.45) • After track cut (# Tracks≤2) • After Track&Fisher cut(FisherResp>0.05) • Only PhotonID cuts • Fisher Cut reducesQCD most in lowest ETbins (cuts millions of QCD) • Similar result for endcap [appendix slide 36] Scaled to 200pb-1 -grec(Original) -grec (# Trk ≤2) -grec (# Trk ≤ 2&Fisher cut) -grec (Photon ID)

  8. Results for g’s • ET distribution of the grec from g+jet • Original (ET>20GeV, H/E<0.2, |h|<1.45) • After track cut (# Tracks≤2) • After Track&Fisher cut(FisherResp>0.05) • Only PhotonID cuts • First three overlap on graph • Most losses in lowest ET bins • Similar result for endcap [appendix slide 37] Scaled to 200pb-1 -grec(Original) -grec (# Trk ≤2) -grec (# Trk ≤ 2&Fisher cut) -grec (Photon ID)

  9. Final g/fakeg Comparison • ET distribution of the grec in Barrel from • QCD (Highest grec in event) • g+jet events (the grecDR matched to ggenfrom hard scattering &passing cuts) • QCD (passing cuts) • Cuts: • # Tracks in solid 0.4 cone ≤ 2, • FisherResp>0.05 Scaled to 200pb-1 -grec (from QCD originally) -grec(from g+jet passing cuts) -grec (from QCD passing cuts)

  10. Final g/fakeg Comparison • ET distribution of the grec in Endcapfrom • QCD (Highest grec in event) • g+jet events (the grecDR matched to ggenfrom hard scattering &passing cuts) • QCD (passing cuts) • Cuts: • # Tracks in solid 0.4 cone ≤ 2, • FisherResp>0.05 Scaled to 200pb-1 -grec (from QCD originally) -grec(from g+jet passing cuts) -grec (from QCD passing cuts)

  11. Summary • Official Loose PhotonID cuts on ET isolation results in significant losses of g’s as ET increases • Instead: In a solid cone, require number of tracks ≤ 2 to remove majority of QCD yet retains majority of g’s • After cutting on number of tracks, training a Fisher with the 10 listed variables and cutting on the result: • Removed an additional ~70% of QCD while keeping 90% of g’s • Did not result in increasing g loss as ET increased • More work needs to be done for ET <200 GeV, where fake g’s still outnumber true g’s

  12. Appendix Slides

  13. Photon ID • These are parameters set for reco::PhotonID isolation calculations /RecoEgamma/PhotonIdentification/python/photonId_cfi.py: isolationtrackThreshold = cms.double(0.0), TrackConeOuterRadius = cms.double(0.4), TrackConeInnerRadius = cms.double(0.04), EcalRecHitInnerRadius = cms.double(0.06), EcalRecHitOuterRadius = cms.double(0.4), EcalRecHitEtaSlice = cms.double(0.04), EcalRecThresh = cms.double(0.0), HcalRecHitInnerRadius = cms.double(0.1), HcalRecHitOuterRadius = cms.double(0.4), HcalRecHitEtaSlice = cms.double(0.), HcalRecHitThresh = cms.double(0.0),

  14. Fisher Input, Barrel 1/2

  15. Fisher Input, Barrel 2/2

  16. Fisher Input, Endcap 1/2

  17. Fisher Input, Endcap 2/2

  18. Results for fake g’s • ET distribution of the grec from dijet QCD • Original (ET>20GeV, H/E<0.2, |h|<1.45) • After track cut (# Tracks≤2) • After Track&Fisher cut(FisherResp>0.05) • Only PhotonID cuts • Fisher Cut reducesQCD most in lowest ET bins • Similar result for barrel [slide 32] Scaled to 200pb-1 -grec(Original) -grec (# Trk ≤2) -grec (Pass Fisher) -grec (Photon ID)

  19. Results for g’s • ET distribution of the grec from g+jet • Original (ET>20GeV, H/E<0.2, |h|<1.45) • After track cut (# Tracks≤2) • After Track&Fisher cut(FisherResp>0.05) • Only PhotonID cuts • First three overlap on graph • Most losses in lowest ET bins • Similar result for barrel [slide 33] Scaled to 200pb-1 -grec(Original) -grec (# Trk ≤2) -grec (Pass Fisher) -grec (Photon ID)

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