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Accurate Wγ/Zγ Cross Section Calculation Methodology for Particle and Parton Levels

Utilizing MCFM 6.1 to predict fiducial cross sections, correcting for parton-particle level disparities, jet definitions, and photon isolation variations. Compare ATLAS and CMS methodologies.

kennethphillips
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Accurate Wγ/Zγ Cross Section Calculation Methodology for Particle and Parton Levels

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  1. Wgam/Zgam Xsec calculation Zhijun Liang University of Oxford

  2. Wgam/Zgam NLO predictions using MCFM • MCFM 6.1 is used to predict Wγ/Zγfiducial cross section in Parton level. • Input card example: • /afs/cern.ch/user/z/zliang/public/forCMS/input.DAT 1fb-1 Wgamma/Zgamma paper arXiv:1205.2531

  3. Parton /particle level predictions • (Parton level): predicted by MCFM. • Particle level: • Measure the scale factor using Alpgento correct for parton to particle level • Correct for jet definitions difference between two levels. • Correct for photon isolation difference between two levels. 1fb-1 Wgamma/Zgamma paper arXiv:1205.2531

  4. Backup

  5. ATLAS Vs CMS • Photon isolations (using relative isolation e_h) • CMS : e_h<0.15 (harder cut on photon isolation) • ATLAS : e_h<0.5 • The difference in these choice is less than 5% • Kinematics selections: • ATLAS : fiducial regions ( with all pT/eta cuts ) • CMS : Total phase space regions. • phase space without lepton pT/eta cut • Photon pT>15GeV , no eta cuts • Renormalization /fragmentation scale • CMS : dynamic scale • ATLAS : fixed scale on W (or Z) mass for Wγ or Zγ. • The difference between these two choice is very small (<2%). • CMS MCFM input cards are for total cross section • /afs/cern.ch/user/p/poter/public/VG_MCFM/input.DAT • ATLAS MCFM input cards are for fiducial cross section • /afs/cern.ch/user/z/zliang/public/forCMS/input.DAT

  6. Only compare MCFM the inclusive cross section prediction • CMS input cards are for total cross section • /afs/cern.ch/user/p/poter/public/VG_MCFM/input.DAT • ATLAS input cards are for fiducial cross section • /afs/cern.ch/user/z/zliang/public/forCMS/input.DAT MCFM Input card Comparison ATLAS input cards CMSinput cards

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