170 likes | 399 Views
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++.
E N D
Status of NLOjet++ for dijet angular distributions Lee Pondrom 21 September 2009
ETave compared to mjj These two scales were fit to the data in Pythia
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.
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
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.
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.
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.
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++.