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ARC: Gautier Hamel de Monchenault, Jeffrey Berryhill

ARC: Gautier Hamel de Monchenault, Jeffrey Berryhill. CMS PAS EWK-09-006. Wednesday July 8, 2009. The “candles” and the “ladders”. masses ( ll ,lv ). scaling/ratios. aka “Berends-Giele” scaling. ☐ FULLY DATA-DRIVEN METHODS: READY TO BE APPLIED ON FIRST DATA. The Program.

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ARC: Gautier Hamel de Monchenault, Jeffrey Berryhill

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  1. ARC: Gautier Hamel de Monchenault, Jeffrey Berryhill CMS PAS EWK-09-006 Wednesday July 8, 2009

  2. The “candles” and the “ladders” masses ( ll ,lv) scaling/ratios aka “Berends-Giele” scaling ☐ FULLY DATA-DRIVEN METHODS: READY TO BE APPLIED ON FIRST DATA

  3. The Program • Test of the “Berends-Giele” (BG) scaling in W+n to W+(n+1) jets and double ratio • Relative measurement • Use different jet definitions (here: calo-, track-, corrected, PF) • Use electron and muon channels • Synchronize W+jets and Z+jets selections for cancellation of efficiency errors in the double ratio • Data control samples for heavy-flavor (hf) enriched background component (top) to the W+jets • Z-candle provides data control sample for W+jets • Predict W(+>=3,4) jets from the low jet multiplcities

  4. Double Ratio: general strategy Event Reconstruction and Cut-Based W+jets, Z+jets selection Maximum Likelihood Fits Background control samples Tests of the fits, PDF validations Predict W + ≥ 3,4 jets

  5. W/Z synchronized selection • Common selection requirements: • Single non-isolated HLT lepton trigger • Electron/muon reconstructon • Lepton identification (ele only)* • Lepton isolation* • Lepton - PV compatibility • Jet clustering • Electron(s) from W(Z) cleaning from jet collections • Jet counting * for Z, asymmetric id+iso • W specific requirements: • >= 1 lepton • Z mass veto • extra muon veto (e) • MET > 15 GeV (QCD rejection) • Z specific requirements: • >= 2 leptons • Z mass window orthogonal selection • Yields and ratio determination: • Maximum Likelihood fit • Efficiency correction of yields, if needed

  6. Lepton reco + ID • Lepton Identification • PixelMatch GSF electron tight ele-ID (W, see table - tight+loose for Z legs) • GlobalMuon • Lepton vertex requirements: • consistency with event primary vertex • Relative tracker + ECAL + HCAL isolation (electron) • Relative tracker + absolute ECAL + HCAL isolation (muon) tight ele-id electron iso cuts Tight id and iso optimized for W+jets: used for W and Z ‘high pT leg’ (use egamma POG loose ID and iso for ‘low pT leg’) cone size muon iso cuts cuts

  7. Jet definitions • For W/Z + jets selection, everything is done as a function of inclusive jet multiplicity • We consider several types of jets (SISCone algorithm): • calo-jets: jets clustered from the calorimeter (ECAL+HCAL) cells re-projected w.r.t. event primary vertex • track-jets: jets clustered from tracks consistent with the event primary vertex • corrected calo-jets: synchronized with the above calo-jets definition • Particle Flow jets: synchronized with the above calo-jets definition These types of jets • have orthogonal detector systematics: calorimeter vs tracker • probe different regions of phase space: 30 vs 15 in pT, 3.0 vs 2.4 in h pT > 30 GeV/c, |h| < 3.0 pT > 15 GeV/c, |h| < 2.4 pT > 60 GeV/c, |h| < 3.0 pT > 60 GeV/c, |h| < 3.0

  8. maximum likelihood fit • signal, backgrounds yields extracted on data with extended, maximum likelihood fit Z+jets: 1dim fit: P=PDF(mee) W+jets: 1dim fit: P=PDF(mTW) total number of events entering the fit (i.e. extended likelihood) • Ni=signal and backgrounds yields • Z+jets: i=signal, tt • W+jets: i=signal, tt+QCD, Z+jets 10

  9. Z MLFit Z Maximum Likelihood Fit Background control sample as in the Z+jets ‘candle’ (EWK-08-009)

  10. Top challenge in W+j • 2-category ML fit: • Heavy-flavor enriched (top-like) • Heavy flavor depleted (signal-like) • Design ‘event impact parameter’ variables to perform at 100 pb-1 • Validate using b-tags • Design all data control samples to extract shapes and efficiencies

  11. 2-category ML fit

  12. W ML Fit (electrons) W Maximum Likelihood Fit Background control sample

  13. W ML Fit (muons) W Maximum Likelihood Fit Background control sample

  14. top, W control samples from the data

  15. ML Fits

  16. ML Fits

  17. Berends scaling in W+jets

  18. Berends scaling in W+jets

  19. Ratios and Double Ratios ☐ Results on double ratios stable for different jet-definitions and electron and muon final states. Cancellation of systematics important for first measurements

  20. W/Z Ratio

  21. Implication: Predict W+3,4 jet rates ☐ More precise than the expected NLO and NNLO calculations expected to be finalized in the next years

  22. Conclusions Analysis presented: a data-driven strategy to measure production of W+jets with 100pb-1 at √s=10 TeV a data-driven strategy to measure production of Z+jets to be used as a denominator in W/Z ratio control samples on data and validation strategies on data reduced impact of energy scale on the W/Z ratio Goals achieved: shown that W+n jets over W+(n+1) jets is constant as a function of n used the slope to estimate high multiplicities better than measurement shown that W+n jets / Z+n jets ratio is also constant as a function of n used the ratio to estimate high multiplicities better than measurement

  23. Backup Slides

  24. Supporting Notes • AN 2009-092 • AN 2009-045 • AN 2008-105 • AN 2008-096 • AN 2008-095 • AN 2008-092 • AN 2008-091 CMSSW_2_1_X CMSSW_1_6_X

  25. Datasets CMSSW_2_1_X Fall08 Summer08

  26. W signal shapes control samples Anti-electron control sample All yields normalized to 100 pb-1 of integrated luminosity Anti-muon control sample

  27. Signal hf efficiency control sample All efficiencies reflect expected precision with 100 pb-1 of integrated luminosity

  28. Top hf efficiency control sample Top control sample for hf efficiency All yields normalized to 100 pb-1 of integrated luminosity ttbar shapes for hf selection variables

  29. event hf-variables Define event variables which use track impact parameters to maximize the probability to find the flying b-quark in the ttbar jets: Jet-variable Event-variable

  30. hf-categories heavy flavour depleted region (signal region): events passing squared DEVTxy - DEVTz cut heavy flavour enriched region (ttbar region): events failing cut on one of the two variables muons: Dxy/zEVT< 100 μm for both calo/track jets electrons: Dxy/zEVT< 180 (80) μm for calo(track) jets definition of the two regions optimized minimizing the statistical error (W+≥3jets). The optimal point is the same as in the worst case scenario [no mT(W) discriminant power] in this way we do not use the full info but only “yes/not” (safer at startup) W/top ratio hf-efficiencies taken from data control samples

  31. From theory to the experiment Crucial test of the QCD theory: factorization theorem cross sections evaluators: @NLO up to W/Z+2jets matrix-element MC’s (i.e. parton level) unitary parton-jet transition (exp: perfect jet reconstruction) parton showers: from partons to observable hadrons Z, W boson fj(x,Q): PDFs fj(x,Q): PDFs FSR ISR FSR underlying event hard scattering parton(s) ISR transition to hadronic observable: hadronization, fragmentation, jet definition, efficiencies,... jets

  32. from the SM to terra incognita W/Z+jets have large cross section at LHC: dominant background for SM measurements: eg. ttbar, Higgs: and for searches: new heavy particles may produce W/Z, with jets from ISR or FSR jets also from the decay of the new heavy particles additional jets are at a cost in SM: O(10) (αs) σ(Z→ll)/σ(W→lν) ≈ 0.1 cross sections factor x 10-100 higher than Tevatron

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