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Status of NLOjet++ for dijet angular distributions

Status of NLOjet++ for dijet angular distributions. Lee Pondrom 21 September 2009. First correct the data to the hadron level using Pythia MC. Corrected data agree well with hadron level Pythia Q 2 =p T 2. Run nlojet++ 10 10 events  0 =E T avge. Vary  0 in NLOjet++.

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Status of NLOjet++ for dijet angular distributions

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  1. Status of NLOjet++ for dijet angular distributions Lee Pondrom 21 September 2009

  2. First correct the data to the hadron level using Pythia MC

  3. Corrected data agree well with hadron level Pythia Q2=pT2

  4. Run nlojet++ 1010 events 0=ETavge

  5. Vary 0 in NLOjet++

  6. ETave compared to mjj These two scales were fit to the data in Pythia

  7. Compare lo and nlo 0=ETaveK factor 1.1

  8. Compare lo and nlo 0=mjjK factor 1.44

  9. 2->2 born level calculations, Pythia • Pythia ‘stand alone’. 1E6 events • All initial and final radiation turned off: mstp(61)=mstp(71)=mstp(81)=mstp(111)=0. No CDFSim. Q2=pT2mstp(32)=2. • QCD processes msub(381)->msub(388) switched on.(qq->qq etc). • Ckin(1)=400, ckin(3)=90, lower limits on ŵ, and on pT . Same cuts in the main CDF MC.

  10. 2->2 born calculation with nlojet++5E9 events • nlojet++-2.0.1. Driver example_chi_lo.cc • Line 159 pdf.mode(pdf_cteq6::lo); • In submitCommand_born to Condor • Executable = /afs/hep.wisc.edu/user/pondrom/nlo/nlojet++-2.0.1/nlojet/nlojet++ • Arguments = -n born_mjj$ZZ -c born -u example_chi_lo.la --max-event 50000000

  11. Cuts in nlojet++ • For 2 partons with highest ET • ET>10 GeV • ||<2 • Cone size D=0.7 in (,) space • Rsep = 1.3. D and Rsep govern when the third parton is included with one of the other two to form a ‘jet’. Should have no effect on a born calculation.

  12. Jet_chi_lhapdf.f • A short fortran program to calculate angular distributions from 2->2 formulas. • Uses CTEQ6. qmass=pT in pdf call and in s. • Calculates  distributions at discreet masses 600,700,800,900 GeV. • No cuts.

  13. 2->2 born comparedPythia,nlojet++,and jet_chi.

  14. 2->2 and full Pythia compared

  15. Conclusions from this exercise • 2->2 Pythia and full Pythia at the parton level look the same. ISR and FSR have little effect. • Hadron level Pythia looks like the data. • Nlojet++ born does not agree with 2->2 Pythia.

  16. Status • The large K factor for mjj is reason to be suspicious of the accuracy of the nlo calculation for that scale. • Etave has a more modest scale differece between lo and nlo calculations. • Pythia fits the data better than nlojet++ • I have not achieved as good a limit on quark substructure using hadron level Pythia or nlojet++.

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