Description

A study for p + pbar-> Higgs or WW and other physics processes at Tevatron CM Energy 1.96TeV in NLO/NNLO calculation.

Methods

• There are two ways to study NLO effact:
  • Generate Unweighted events: For Higgs, we can only use MC@NLO
  • Event Reweighting based on ratio of NLO to LO spectrum: It could be done by all generators. For Higgs, reweight based on two variables (pT, Rapidity)
• For NNLO, we can only use Event Reweighting methods.

NLO Generator

MC@NLO

• MC@NLO is a standalone matrix element generator which matches Next-to-Leading-Order calculations of rates for QCD processes with a parton shower Monte Carlo event generator (HERWIG)
• homepage: http://www.hep.phy.cam.ac.uk/theory/webber/MCatNLO/
• Authors: Stefano Frixione and Bryan Webber
• David Water's notes for MC@NLO, Oct 8 2003, html
• CDF Note 7769: Documentation for the UserInfo? and UserInfoColl? classes -- useful for storing event weights.
• Jason Galyardt's notes
• Web Lecture by Stefano Frixione ( INFN ), Jun 24 2004, html

GR@PPA - GRace At Proton-Proton/Antiproton collisions

• A GRACE -based event-generator framework for high energy hadron-collision interactions. The program can be embedded in a general-purpose event generator PYTHIA and HERWIG , to add initial- and final-state parton showers and the simulation of hadronization and decays.
• homepage: http://atlas.kek.jp/physics/nlo-wg/grappa.html
• Authours: Soshi Tsuno, et. al.
• W+jets study at CDF Tsuno's study
• It can generate W/Z/WW/WZ/ZZ/ttbar/QCD/4bjets + njets

NLO Calculation

MCFM - Monte Carlo for FeMtobarn? processes

• It can generate LO but not NLO unweighted events. It provides NLO calculations of Higgs/ttbar/Ewk/QCD processes
• homepage: http://mcfm.fnal.gov/
• Authors: John Campbell, Keith Ellis
• Configuration:
  • technical.DAT: Use Spira's Higgs BR and Width results

 .true.          [spira]

• Tips: Compiled MCFM to generate LO unweighted events in HBOOK ntuple format

   1. Compile mcfm with CERNLIB 
      A edit Install script
            set CERNLIB     =    /home/cdfsoft/products/cern/2004/Linux+2.4/lib
      B. Generate a makefile
            ./Install 
      C. edit makefile
            NTUPLES = YES
      D. Compile, type make
         In the end, you'll see these messages.
          ----> MCFM compiled with its own PDFs only <----
          ----> MCFM compiled with optional n-tuple output <----        
   2. Generate n-tuple with mcfm. You can only generate LO unweighted events. Reseed to generate more statistics
       Edit input.DAT
       .true.         [creatent]  //create ntuple
       1089            [ij]         //different random number seed

   3. Convert hbook file to root file
       h2root [hbookfile] [root filename] 

NNLO Calculation

FEHiP? - Fully Exclusive Higgs Production

• It cannot generate unweighted events but can calculate LO/NLO/NNLO cross sections of Higgs. Higgs can only decay through H->gamma gamma channels.
• homepage: http://www.phys.hawaii.edu/~kirill/FEHiP.htm
• Authors: C. Anastasiou , K. Melnikov and F. Petriello.
• The ppbar collision is not implemented in the default source codes. Frank Petriello provides us three modified files for ppbar calculations. Shih-Chieh adds four new parameters for different Higgs (Pt, Rapidity) cuts.src codes
• Edit constraint.F to implement event selection cuts. However, there are no histogram output from FEHiP? . We should consider implement by ourselves.
• A comparison of Higgs Pt/Eta spectrum to Pythia is done

• The finner binning shows that there are negative contributions for lowest Pt bin. Why is that?

PDF

• PDF used by Pythia@CDF

  'cteq5_l'              [pdlabel]
  4                         [NGROUP, see PDFLIB]
  46                       [NSET - see PDFLIB]
  MRST98.LHpdf  [LHAPDF group]
  1                         [LHAPDF set]
     

Others

• Higgs-boson pT in gluon fusion, by Russel P. Kauffman, Phys. Rev. D 44, 1415–1425 (1991), pdf: The mass dependent pT spectrum of Higgs.
• Simulating the H→WW→llnunu Channel by Anne-Sylvie Giolo-Nicollerat, May 22 2006, pdf: Good talks about Higgs pT spectrum effacts
• hep-ph/0604077: Combining Monte Carlo generators with next-to-next-to-leading order calculations: event reweighting for Higgs boson production at the LHC, Giovanna Davatz, Fabian Stoeckli, Charalampos Anastasiou, Guenther Dissertori, Michael Dittmar, Kirill Melnikov, Frank Petriello, JHEP 0607 (2006) 037: Event reweighting study by using FEHiP? , MC@NLO and Pythia
• D0's simulation group: A good summary of MC generators

-- ShihChiehHsu - 23 Oct 2006