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Hadronic Event Shape Variables in pp collision at 7 TeV

Hadronic Event Shape Variables in pp collision at 7 TeV. Introduction Data-set and Event Selection Comparison of Basic Jet Objects in Data and MC Event Shape Variables in Data and MC Systematics and Sensitivity Final Results Summary.

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Hadronic Event Shape Variables in pp collision at 7 TeV

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  1. Hadronic Event Shape Variables in pp collision at 7 TeV • Introduction • Data-set and Event Selection • Comparison of Basic Jet Objects in Data and MC • Event Shape Variables in Data and MC • Systematics and Sensitivity • Final Results • Summary PAS : QCD-10-013, CMS AN-2010/100 and CMS AN-2010/127

  2. Introduction • Experiment : Normalised Event Shape variables are expected to be robust against jet energy scale uncertainties and jet energy resolution effects • Theory : Calculations of Event Shape variables are carried out in perturbative QCD • Event Shape variables can be used to distinguish different models of QCD multijet production • Possibility with large statistics: measurement of αs Variables are defined in terms of four momenta in the transverse plane, in analogy to e+e− collider,Banfi, Salam, Zanderighi, JHEP 0408 (2004) 62 Central Transverse Thrust Central Thrust Minor

  3. Central Transverse Thrust • Plotted in the natural logarithm, log τ = log(1−T)

  4. MC samples • /MinBias/Spring10-START3X V26A 357ReReco-v2/GEN-SIM-RECO • /MinBias TuneD6T 7TeV-pythia6/Spring10-START3X V26B-v1/GEN-SIM-RECO • /MinBias TuneP0 7TeV-pythia6/Spring10-START3X V26B-v1/GEN-SIM-RECO • /MinBias 7TeV-pythia8/Spring10-START3X V26B-v1/GEN-SIM-RECO • /QCD Ptxx/Summer10-START36 V9 S09-v1/GEN-SIM-RECODEBUG, where range of pˆT from15 GeV/c to kinematic limit (D6T sample, default MC). • /QCD Ptyy-herwig/Summer10-START36 V9 S09-v1/GEN-SIM-RECO, where range of pˆT from15 GeV/c to kinematic limit. • /QCD Pt-yytozz 7TeV-pythia8/Summer10-START36 V10 S09-v1/GEN-SIM-RECO, where yytozz are the range of pˆT from 15 GeV/c to kinematic limit. • /QCDxxJets Ptyytozz-alpgen/Summer10-START36 V9 S09-v1/GEN-SIM-RECO, where xx = 2,3,4 and 5, yytozz are the range of pˆT ranges from 40 GeV/c to kinematics limit. • /QCD Ptyytozz-madgraph/Summer10-START36 V9 S09-v1/GEN-SIM-RECO, where yytozz are the range of pˆT from 50 GeV/c to 500 GeV/c. • CMSSW_3_6_1    and    Spring10 jet corrections  

  5. Data and MC event samples • Data : • 1. /MinimumBias/Commissioning10-SD JetMETTau-Jun14thSkim v1/RECO (run# 134630 to 135802) • 2. /JetMETTau/Run2010A-Jun14thReReco v2/RECO ( 135821 to 137028) • 3. /JetMETTau/Run2010A-PromptReco-v4/RECO (run# 137437-139790) • 4. /JetMETTauMonitor/Run2010A-PromptReco-v4/RECO (run# 137437-139790) • 5. /JetMETTau/Run2010A-Jul16thReReco-v1/RECO (run# 139779 to 140160) • Cert 132440-137028 7TeV June14thReReco Collisions10 JSON v2.txt, • Cert 132440-139790 7TeV StreamExpress Collisions10 JSON.txt • and Cert 139779-1340159 7TeV July16thReReco Collisions10 JSON.txt • Dataset Luminiosty (nb−1) • Total HLT Jet30U HLT Jet15U • Run2010A-Jun14thReReco v2 4.92 4.92 4.92 • SD JetMETTau-Jun14thSkim 6.64 6.64 6.64 • Run2010A-PromptReco-v4 65.53 65.53 4.71 • Run2010A-Jul16thReReco-v1 124.98 36.60 2.99 • Upto Run 139790 77.09 77.10 16.26 • Upto Run 140159 202.07 113.70 19.25

  6. Event selection • Technical trigger : LHC clock (BPTX) and veto on Beam Halo !(36||37||38||39) • High Level : HLT_Jet15 / HLT_Jet30 • Vertex: at least one primary vertex with |Δz|<15cm, |Δr|<2cm and ndf >4 • Scraping event : less than ten tracks or more than 25% of the tracks with HighPurity • Jet Cleaning (next slide)

  7. Jet algorithms (AntiKt-5) Used all four types of jets • CaloJet • PFJet • JetTPT • Tracker Jet Selection of Jets : (JTF recommendation) • Jet selection : Loose JetId cuts for CaloJet and JetJPT ( n90hits>1, emEnergyFraction>0.01, fHPD<0.98) • PF jet : NeutralEM(Had)EnergyFraction<1.0 • In barrel (|η|<2.4), ChargedHadronEnergyFraction >0, chargedEMEnergyFraction<1.0, charge multiplicity>0 • For all types : At least two objects in jet • Out of all jets with |η|<2.6, two leading jets should be within |η|<1.3 • Leading two jets should pass JetID criteria and PT1 > 90 GeV/c / 60GeV/c • Event shapes are calculated with all jets within |η|<1.3 and Pt >30 GeV/c

  8. Trigger criteria • JetMETTauMonitor_Run2010a_May27thRereco • No matching of Reco and HLT jet, requires one HLT_Jet15 object • In analysis, Pt of leading jet is > 60 GeV/c also analysis with >90 GeV/c • Correction for trigger efficiency in Tracker jet Data |η|<2.6

  9. Event Shape variables (Prel)

  10. Comparison of Basic objects : ΔΦ of leading Jets CaloJet • With |η|<1.3 MC is normalised to total numbers of entries in data • Obviously Alpgen and Pythia8 have bias JetJPT PFJet TrackerJet

  11. Discrepancy in Alpgen sample • Mangano : Alpgen should not looks that different • CMS collegues : Alpgen and Madgraph should be similar • Wrong matching efficiency values on production twiki, which have been corrected now. Thanks to the Generator group (esp. Fabian Stoeckli) for the quick response. Ratio of cross-sections after matching changed for lowest 3j/2j_Pt40-120 –sample from previously 0.18 to now 0.35 due to new evaluated efficiencies Similarly gamma+1-4jet sample also had wrong weight factor (physics-validation/775.html) Nobody has noticed this in last six months !!!!!!!!!!!! sample Old effi New effi 2j_40_120 0.64 0.571 2j_120_280 0.25 0.279 2j_280_500 0.24 0.204 2j_500_5000 0.23 0.192 3j_40_120 0.17 0.299 3j_120_280 0.21 0.207 3j_280_500 0.20 0.144 3j_500_5000 0.17 0.134

  12. Comparison of Basic objects : ΔΦ of leading Jets CaloJet • Discrepancy in Alpgen reduces also close to madGraph, but now main difference in coming from Pythia8 JetJPT PFJet TrackerJet

  13. Comparison of Basic objects : ΔPt of leading Jets CaloJet • Distribution in tracker jets are different from others. Combination of charge and neutral hadrons are different in different models. JetJPT PFJet TrackerJet

  14. Comparison of Basic objects : Pt2 sin(ΔΦ)/Pt1 of leading Jets CaloJet • Deviation in Alpgen and Madgraph are opposite to Pythia8. • Simplue guess : Alpgen/Madgraph, Thrust value is larger, opposite in Pythia8 JetJPT PFJet TrackerJet

  15. Comparison of event shape variables • Data with only statistical error • MC samples • Pythia6 • Pythia8 • Herwig++ • Alpgen • Madgraph • D6T and P0 tuning of Pythia6 are consistent with each other • Herwig+Jimmy is also consistent with Herwig++

  16. Systematic uncertainty and Sensitivity • Systematic uncertainty: • Jet Energy and Position Resolution (on MC) • Jet Energy Scale (on Data) • Eta dependent Jet Energy Scale (on Data) • Sensitivity : • Jet Types • Jet Algorithms • Underlying event • Initial State Radiation • Final State Radiation

  17. Effect of Jet Energy Scale on Event Shape Variables (±5%) : An example Thrust Minor • Most of the sample is common, more (less) events are accepted with increase (decrease) in JES • 3% uncertainty • Effect of eta dependent scale uncertainty is negligible

  18. Jet Energy and position Resolution Uncertainty • Recommendations: - 10 % uncertainty in the sigma of the jet energy resolution curves - compare the distributions with the default sigma, 1.1×σ and 0.9×σ The jet energy resolution uncertainty leads to deviations within 2-4% over most of the range

  19. Comparison of various Jet types in data Minor Thrust • Difference in Different types, is it same in MC too ? All are normalised to total numbers of entries in Calo objects

  20. Effects of Jet constituents/Algorithm on the comparison of Data and MC • Double ratio : (Type1/Type2)Data / (Type1/Type2)MC Only one (maximum) error in Data and MC are considered Consistent with ONE, but need more statistics

  21. Effects of Jet Pt/eta criteria • Double ratio : (Sel1/Sel2)Data / (Sel1/Sel2)MC In PAS Consistent with ONE, but need more statistics Consistent with one, but need to look with larger statistics

  22. Stability over time

  23. Results Yellow Error band contains systematicand statistical uncertainties on data and MC,the black error bar shows the statistical error on Data only Pythia and Herwig++ are close to the data, Alpgen,Madgraph and Pythia8 show large discrepancies

  24. Thrust Minor and Y23 Minor Y23 • Pythia8 differs in Thrust/Minor, but not in Y23, splitting of jets into two looks fine in pythia8. Very sensitive to αS

  25. Comparison with two and three jet events • With only two jet events, Alpgen/Madgraph and Pythai8 differ from data, which was predicted from simple Pt2 sin(ΔΦ)/Pt1 distribution 2-jet 3-jet

  26. Comparison with Pt> 45 and 60 GeV on all jets • Same as 30 GeV criteia 45GeV 60GeV

  27. Central Thrust and Thrust Minor with 60GeV crit (HLT_Jet15U) Thrust Minor • Same as 90GeV/c criteria

  28. Summary • First measurements of central event shape variables from pp collision data at cm energy of 7 TeV • Several types of jets are used in the analysis : CaloJet, JetJPT, PFJet, TrackerJet • Systematic uncertainty in the measurements studied due to • Jet energy scale (constant as well as η dependent scale) • Jet energy and position resolution for MC predictions • Measurements are compared with several QCD inspired models • Reasonable agreement with different tunes PYTHIA6 and HERWIG(++) • ALPGEN, MADGRAPH and PYTHIA8, with default CMS parameter tunes, show significant discrepancies with data • Talked with different Generator people about this discrepancy

  29. Central Thrust and Thrust Minor with only two jet events Thrust Minor • Same as all events

  30. Comparison of Basic objects : PT of leading jets • Looks fine

  31. Comparison of Basic objects : Pesudorapidity • A dip in Data around |eta|=1.3

  32. Comparison of Basic objects : Azimuthal angle • A periodicity is observed, less in tracker jet

  33. JetJPT trigger With matching Trigger jets within Δr < 0.15

  34. Systematic/Sensitivity • But used only JER, JES, JES(η) V01-09-01-09 CondFormats/JetMETObjects V00-02-13    CommonTools/RecoAlgos V03-28-04    DataFormats/JetReco V04-03-05    RecoJets/JetProducers

  35. Effect of inter calibration of calo towers (4%) Minor Thrust • Most of the sample is common • Average shift is ~2%

  36. Effect of Jet cleaning criteria, loose vs tight Minor Thrust • Calo : JPT : + fHHP < 0.95 and EMfrac<0.9 • PF : + EM(HAD)energy fraction < 0.9 • Rejection : 6.0/3.6/0.9 for CaloJet, JetJPT, PFJet Samples differ by 3% only, effect <1% effect

  37. Comparison of various Jet Algorithms Minor Thrust • Observe a variation, which is expected due to different algorithms

  38. Trigger criteria of Tracker Jet

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