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MC Generators for CMS

MC Generators for CMS. Overview of the CMS MC Generator group: activities and tasks. Paolo Bartalini, University of Florida Filip Moortgat, ETH Zurich. Mini-Workshop on Early CMS Physics , Fermilab, June 8 2007. MC Generators vs CMS organization.

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MC Generators for CMS

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  1. MC Generators for CMS Overview of the CMS MC Generator group: activities and tasks Paolo Bartalini, University of Florida Filip Moortgat, ETH Zurich Mini-Workshop on Early CMS Physics, Fermilab, June 8 2007

  2. MC Generators vs CMS organization • New CMS management -> CMS Physics Groups recently re-organized. • The emphasis is on the early measurements and their impact on detector commissioning/calibration activities • CMS MC Generator Tools (F. Moortgat, P. Bartalini) • Implementing and maintaining generator interfaces in CMSSW • Organizing MC production requests -> Spring 2007, CSA07 • Validating/comparing generators & related tools • MC tuning • All this happens after two important 2006 milestones • The publication of the CMS Physics TDR • Generator framework frozen to provide a stable reference -> sticking with the Fortran based CMKIN • The CSA06 exercise • Emphasis on Computing issues (data transfer between Tiers etc.) -> Migration of the MC generators in CMSSW started -> MC Validation & Tuning activities not particularly relevant As a consequence current relevant MC Tuning & Validation activities are still a bit ALPGEN & Pythia centric Fundamental validation tests (Sanity Checks, Basic Conservation Properties) are of course also ongoing for all the other Monte Carlo generators (see next slides) More information at https://twiki.cern.ch/twiki/bin/view/CMS/GeneratorMain

  3. Generators in CMSSW (1) GeneratorInterface in CMSSW: Pythia6Interface +++H. Naves, F. Moortgat Herwig6Interface +++F. Stoeckli (including Jimmy) Pythia8Interface ++M. Kirsanov Herwig++Interface +(expression of interest, Karlsruhe) SherpaInterface +(expression of interest, Karlsruhe) HydjetInterface ++C. Mironov TopRexInterface ++S. Slabospitsky MC@NLOInterface +++F. Stoeckli ALPGENInterface ++M. Pierini, M. Spiropulu MadGraphInterface +++D. Kcira, M. Hansen (also works for Phantom and Helac) (S. Bolognesi, F.M.) CompHepInterface ++S. Slabospitsky, D. Konstantinov EvtGenInterface +U. Langenegger, R. Covarelli

  4. Generators/Tools in CMSSW (2) Continued: ExHumeInterface +++A.Vilela Pereira PomwigInterface +++ A.Vilela Pereira LHAPDF ++H. Naves, F.M. CosmicMuonGenerator +++P. Biallass BeamHaloGenerator ++E. Perez ParticleGuns ++J. Yarba MCFileReader ++J. Weng NtupleConverter ++J. Weng GENSER1 / GENSER2 Libraries are adopted, if available & no need to modify More information https://twiki.cern.ch/twiki/bin/view/CMS/GeneratorTaskList +++ = advanced ++ = ongoing + = resources identified

  5. News in CMSSW_1_4_X • new HepMC version from LCG (event record) • new HepPDT version from LCG (particle data table) • code reorganization: all generator interfaces and filters • in “GeneratorInterface” • Pythia version 6.409: includes (optional) new parton shower and underlying event model, SLHA interface and quarkonia production • HERWIG/Jimmy included • MC@NLO included • LHAPDF included • Cosmic Muon Generator updated • Two dedicated diffractive generators included • Run section will include cross section (2) and filter efficiency

  6. Spring07 status https://twiki.cern.ch/twiki/bin/view/CMS/GeneratorProduction2007 • Spring07 GEN-SIM production with CMSSW_1_2_3 basically done. • ~35 M events (~500 requests) done • few late/special requests still ongoing • DIGI-RECO of these samples with CMSSW_1_3_1 is ~90% done: • Total: ~50M events processed / month

  7. Spring07 status (2) • for details about specific samples : • 1) production status: • https://cmsdoc.cern.ch/cms/test/aprom/DBS/prodrequest/ProdRequest/getAllRequestsPage • 2) data location: (! Use DBS-2 site!) • http://cmsdbs.cern.ch/DBS2_discovery/ • All data will by default go to CERN/FNAL • You can request the data to go to specific sites using Phedex: • http://cmsdoc.cern.ch/cms/aprom/phedex/

  8. CSA07 plan • CSA07 Production: 100M CSA07 “Standard Model” cocktail: • Min bias (20 Mevt) • QCD jets (25 Mevt) and +jets (5 Mevt) • Electrons/muons from b-decays (20 Mevt) • Drell-Yan and Onia (10 Mevt) • W/Z (plus jets) (15 Mevt) • Top (5 Mevt) PYTHIA ALPGEN Will be produced with CMSSW_1_4_X (GEN+SIM) and CMSSW_1_5_X (DIGI+RECO) • details (developing): see • https://twiki.cern.ch/twiki/bin/view/CMS/GeneratorProduction2007CSA07 • Summer07 production: all signal samples and background samples • missing in the above will be produced at the Tier-2’s

  9. May mini workshops • Recent activities: two mini-workshops in May: • May 14th: MC Tuning mini w/s • May 21st: ALPGEN Generation mini w/s Agenda MC Tuning workshop:

  10. The MC Tuning Goals • To provide both Best and Error settings for • Hard process description • Hard process scale • PDF description • QCD radiation • Fragmentation of light and heavy quarks • Minimum Bias (including the variations in the relative amount of diffractives etc.) • Underlying Event • Decays • Etc. Some guidelines available in CMS Note 2005/013 (To be reviewed) Big Issue for “Predicting” at the LHC ==> Energy Dependency of the Parameters Often need to make compromises: no LO PDF Error Sets, etc. See also talk of Rick Field, This Morning

  11. Relaxing the momentum sum rule: LO* LO* performs better than LO and NLO in both cases [R. Thorne]

  12. PYTHIA 6.2 Tunes Use LO as with L = 192 MeV! K-factor (Sjöstrand) UE Parameters ISR Parameter Intrensic KT Now also D6 and D6T available (Tunes with CTEQ6L PDFs) [Rick Field] Two different solutions for the energy dependency of the PT cut-off in MI ==> Define methodology to estimate some of the theoretical uncertainties

  13. UE: Application to muon isolation in H4msearch (suppression of tt and Zbb backgrounds) 1. How well can we predict the isolation cut efficiency using the current Monte Carlo generators? 2. Can we calibrate the isolation cut efficiency using the experimental data themselves and, if yes, would the associated experimental systematic errors be smaller than the Monte Carlo based theoretical uncertainties? • Isolation parameter is a sum of PT of tracks inside a cone dR(η,φ) = 0.3 • (PT of considered tracks > 0.8 GeV) Random cone direction: all the calculations for isolation observable done for uniformly distributed random directions in event instead of directions for 'real' muons. 5% uncertainty only in one cut 2% relative uncertainty w.r.t. Drell-Yan -3σ case (smaller PTcut-off) -0σ case (default PTcut-off) +3σ case (greater PTcut-off) [CMS Note 2006/033]

  14. Quarkonia also prefers dampening... Phys. Rev. D71: 032001, 2005 Total Color octet Color-singlet NRQCD PYTHIA NRQCD PYTHIA CTEQ6L|y|<0.6 Total Color octet Color-singlet CTEQ6L|y|<0.6 CDF data pT0=2.85 GeV nice agreement • disagreement at low PT [M.Bargiotti] [M.Bargiotti] Regularization natural: gluon exchange in the t channel d/dPT2 ~ 1/ dPT4 LHC Predictions: Let’s assume universality: same PT0 of MPI, same energy dependency!

  15. PYTHIA 8 vs. CDF for the J/y Similar but not “universal” for Y Good agreementfor pT above 2 GeV/c [C. Lourenco]

  16. Validation of Pythia 6.2 vs6.3vs6.4based on MB and UE Analyses in CMSSW The candidates (charged particles) are created and used to define the observables at generator level Results are summarized in terms of: + charged spectra + charged jet kinematics + MB and UE observables UE&MB@CMS CMSSW Package: AnalysisExamples/MinimumBiasUnderlyingEvent [L. Fano’]

  17. Minimum Bias: basic kine observables on charged tracks 6.2 6.3 6.4 More soft charged in 6.4?

  18. Minumum Bias: MB and UE observables Df “Toward” “Transverse” “Transverse” “Away” Softer charged spectrum more evident ? 6.2 6.3 6.4 transverse toward away away In UE observables, charged are selected with PT>0.5

  19. MPI Model effect on Long  range correlations central forward no correlation long range correlation Pythia without MI -> no correlation Pythia with MI: Long range correlations, trigger enhancing differences in the central region Generator Level Studies with Pythia 6.409 [K.Borras] (Thanks to P.Skands for making available PYTUNE)

  20. Diffractive peak Leading protons Simulation of forward protons What do we expect ? p Universal number Same for ep, pp No surprise: vertex factorisation xL=P’/Pbeam [Grothe, Ruspa] Fastest proton in the event

  21. Simulation of forward protons What we find... Pythia approx OK in diffractive peak (after removing elastic component, not there in HERA data) Pythia wrong in shape and normalisation outside diffractive peak (approx factor 2-3) Re-weighting adopted [Grothe, Ruspa] xL=P’/Pbeam Phojet slightly worse than Pythia Fastest proton in the event

  22. Example of Automated Validation Results of an automated PERL script which allows to run the same CMSSW job with all the versions of a MC generators available in GENSER All charmonia processes (ISUB = 421-439) have been chosen. No cross-section reweigthing has been applied. Cross-sections are for all included subprocesses. Pythia version Events generated Total cross-section (mb) 6_325 100000 1.130E+01 6_326 100000 1.130E+01 6_327 100000 1.130E+01 6_400 100000 1.130E+01 6_402 100000 1.130E+01 6_403 100000 1.130E+01 6_404 100000 1.130E+01 6_405 100000 1.130E+01 6_406 100000 1.370E+01 6_409 100000 1.370E+01 The transition apparently happens when going from Pythia version 6_405 to version 6_406. Please find Pythia release notes under the following URL's: Pythia 6.3 : http://www.thep.lu.se/~torbjorn/pythia/pythia6327.update Pythia 6.4 : http://www.hepforge.org/downloads/Pythia6 [F. Bechtel]

  23. Other Examples of Automated Validation from LCG http://lcgapp.cern.ch/project/simu/generator/genval.html

  24. ALPGEN mini workshop I. Segoni

  25. ALPGEN processes ALPGEN production/validation for Spring07 production Work in close collaboration with the ALPGEN authors. New implementations often triggered by the CMS requests for example: matching for QQQ’Q’ to appear in v2.2x

  26. ALPGEN: Computing G. Gomez-Ceballos, M. Klute, D. Evans, A. Fanfani • cmsGenscript has been written for ME generation (before cmsRun) • https://twiki.cern.ch/twiki/bin/view/CMS/CmsGen • https://twiki.cern.ch/twiki/bin/view/CMS/ProdAgentDevelopmentPlan

  27. ALPGEN: W/Z+jets with VBF preselection iteration 1 iteration 2 iteration 3 iteration 4 ~60 jobs each normalised to 1 iteration 1 iteration 2 iteration 3 ~240 jobs each normalised to 1 [Nikitenko, Greder, Takahashi]

  28. Goal: to Study the Tail of the Boson PT [Pierini, Spiropulu]

  29. Future of MC Tuning & Validation in CMS • A more “inclusive” and “systematic” approach is needed • From basic sanity checks to physics validation for all the supported models • From local tuning/validation to global tuning/validation • Convenient Frameworks need to be evaluated/adopted. • Evaluation phase • Vista • Rivet/JetWeb • Official visit of the PH Generators’ group to Fermilab - Thanks to S.Mrenna, P.McBride etc.

  30. Official visit of the PH Generators’ group to Fermilab Thanks to S.Mrenna, P.McBride etc. Now collecting several expression of interest to contribute to the activities of the CMS Generator Group - Theory, Exp (from CDF, D0 etc.). - Don’t hesitate to contact us ! Tomorrow: MC Generators tutorial (Filip)

  31. BACKUP

  32. CMS PH Organigram

  33. April 2007 MC Meetings (Phys. Days) • Generator Meeting • HELAC - PHEGAS : automatic helicity amplitude calculation and parton level generation (CostasPapadopoulos) • VBFNLO : NLO parton level MC for Vector Boson Fusion (ManuelBaehr) • A simple root format for generator events (OliverOberst ) • SUSY/BSM Meeting • SUSY-HIT and SDECAY status(MiladaMuehlleitner) • B-Physics Meeting • EvtGen Interface Status Report(Roberto Covarelli) • QCD/TOP/EW Meeting • News from MC production (Ilaria Segoni) • Plenary • Vista@CMS: Physics Commissioning (Bruce Knuteson)

  34. MadGraph in CMSSW: Flow of Events Dorian Kcira et al. Package: GeneratorInterface/MadGraphInterface • MadGraph • Generate events • Output partons • LesHouches format • MadGraph • Interface • Generate event • Populate event from input file using • user routines from ME2pythia.f • Parton shower • Hadronization` • Les Houches format • Plain text file Pool File HepMCProduct HEADER: . . . EVENTS: <event> 4 661 0.7533903E-01 0.9118800E+02 0.7818608E-02 0.1300000E+00 21 -1 0 0 502 503 0.00000000000E+00 0.00000000000E+00 0.72071194343E+03 0.72071194343E+03 0.00000000000E+00 0. -1. 21 -1 0 0 501 502 0.00000000000E+00 0.00000000000E+00 -0.14548493253E+03 0.14548493253E+03 0.00000000000E+00 0. 1. 6 1 1 2 501 0 -0.42290358713E+02 -0.12398540766E+03 -0.32583445893E+02 0.22046094144E+03 0.17430000000E+03 0. 1. -6 1 1 2 0 503 0.42290358713E+02 0.12398540766E+03 0.60781045680E+03 0.64573593453E+03 0.17430000000E+03 0. -1. </event>

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