Wgamma NLO Cross Section

Madgraph

• Use MG_ME_V4.5.0 (http://madgraph.hep.uiuc.edu/)
• Madgraph provides LO cross section
• Madgraph does NOT have fragmentation photon
• Selections I (for theoretical cross section):
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  • no cut
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• Selections II (for MC sample):
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  • no cut
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• Selections III (for offline selections for electron channel):
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• Selections IV (for offline selections for muon channel):
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• PDFs: CTEQ6L1
• Factorization and renormalization scales:
  • : the maximum mass of among final states
  • : the index for running over jets and massless visible particles

Baur Wgamma NLO

• Baur Wgamma NLO provides LO and NLO cross sections
• Baur Wgamma NLO has fragmentation photon
• Baur Wgamma NLO does NOT have FSR photon
• Selections I (for theoretical cross section):
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  • no cut
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• Selections II (for MC sample):
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  • no cut
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• PDFs: CTEQ6L1 (LO); CTEQ66M (NLO)
• Factorization and renormalization scales:

MCFM

• Use MCFM 6.0
• MCFM provides LO and NLO cross sections
• MCFM has fragmentation photon
• Selections I (for theoretical cross section):
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  • no cut
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• Selections II (for MC sample):
  • 
  • 
  • no cut
  • 
  • 
• Selections III (for offline selections for electron channel):
  • 
  • 
  • 
  • 
  • 
• Selections IV (for offline selections for muon channel):
  • 
  • 
  • 
  • 
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• PDFs: CTEQ6L1 (LO); CTEQ66M (NLO)
• Factorization and renormalization scales:

Theoretical Cross Section (Selection I)

LO Cross Section

• Nice agreement between MCFM and Madgraph
• The difference between MCFM and Baur Wgamma for photon PT < 50 GeV is reasonable → This is due to FSR contribution
• The difference between MCFM and Baur Wgamma for photon PT > 50 GeV is about 5~10 % → This could be due to factorization and renormalization scales

NLO Cross Section

• The difference between MCFM and Baur Wgamma for photon PT < 100 GeV is reasonable → This is due to FSR contribution
• The difference between MCFM and Baur Wgamma for photon PT > 100 GeV is about 5~10 % → This could be due to factorization and renormalization scales

k-factor

Cross Section for MC sample (Selection II)

LO Cross Section

• Nice agreement between MCFM and Madgraph
• The difference between MCFM and Baur Wgamma for photon PT < 50 GeV is reasonable → This is due to FSR contribution
• The difference between MCFM and Baur Wgamma for photon PT > 50 GeV is about 5~10 % → This could be due to factorization and renormalization scales

NLO Cross Section

• The difference between MCFM and Baur Wgamma for photon PT < 100 GeV is reasonable → This is due to FSR contribution
• The difference between MCFM and Baur Wgamma for photon PT > 100 GeV is about 5~10 % → This could be due to factorization and renormalization scales

k-factor

Cross Section for Offline Selection for Electron Channel (Selection III)

LO Cross Section

• Nice agreement between MCFM and Madgraph

NLO Cross Section

• We are trying two additional methods:
  • Method I (is labeled as Madgraph I):
    • Use Madgraph Wgamma + 0,1 Jet
    • The distributions are normalized to MCFM NLO cross section
    • Some of Madgraph distributions do not agree with MCFM result
  • Method II (is labeled as Madgraph II):
    • Use Madgraph Wgamma + 0,1 Jet
    • The distributions are normalized to MCFM LO cross section
    • Then, the distributions are scaled by k-factor as a function of photon PT
    • The distributions have higher result than Method I
• Does it mean that the phase space of Madgraph Wgamma + 0,1 Jet is closed to NLO Wgamma phase space?
• Will jet matching change these distributions?

k-factor for Selection

Cross Section for Offline Selection for Muon Channel (Selection IV)

LO Cross Section

NLO Cross Section

k-factor for Selection

-- SyueWeiLi - 06-Jun-2011