Photon ID study

Goals

• Ultimate goal: reduce the W + jet background to the W + gamma channel
• Understand the photon fake rate
• Identify variables that can discriminate between prompt and secondary photons.

Strategy

• Choose Photon Identification variables according to their rejection power:
  • Plot Signal eff vs Backgound effs for all the variables.
  • Use those that maximize the background rejection at a fixed signal efficiency.

• List of investigated variables:
  • Cluster shapes:

    sigmaEtaEta	Size of the Cluster in Eta
    sigmaEtaPhi	Size of the Cluster in EtaPhi
    sigmaPhiPhi	Size of the Cluster in Phi
    R9	E(3x3) / E(SC)
    R19	Emax / E(3x3)

  • Isolations

    tracker	Sum Pt(track) in 0.05<DeltaR<R
    ecal	Sum Et(recHits) in DeltaR<R - Et(photon)
    hcal	Sum Et(towers) in DeltaR<R

    calculated in cones of size R = 0.3..0.55

-- PasqualeMusella - 23 Jul 2008