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The Tevatron Connection

The Tevatron Connection. Rick Field University of Florida ( for the CDF Collaboration ). CDF Run 2. Jet Physics in Run 2 at CDF. Outline of Talk. Constructing Jets in Run 2 at CDF (MidPoint and K T Algorithms). New from CDF: The K T -Jet Inclusive Cross Section.

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The Tevatron Connection

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  1. The Tevatron Connection Rick Field University of Florida (for the CDF Collaboration) CDF Run 2 Rick Field - Florida/CDF

  2. Jet Physics in Run 2 at CDF Outline of Talk • Constructing Jets in Run 2 at CDF (MidPoint and KT Algorithms). • New from CDF: The KT-Jet Inclusive Cross Section. High PT “jets” probe short distances! KT Algorithm • New from CDF: The b-Jet Inclusive Cross Section. • New from CDF: The b-bbar Jet Cross Section and Correlations. • Understanding and Modeling the “Underlying Event” in Run 2 at CDF. Rick Field - Florida/CDF

  3. CDF-QCD Group CDF-QCD Group Learn more about how nature works. Compare with theory and work to provide information that will lead to improved Monte-Carlo models and structure functions. Our contributions will benefit to the colliders of the future! • Jet Cross Sections and Correlations: JetClu,MidPoint, KT algorithms. • DiJet Mass Distributions:Df distribution, compositness. • Heavy Flavor Jets: b-jet and b-bbar jet cross sections and correlations. • Z and W Bosons plus Jets: including b-jets. • Jets Fragmentation: jet shapes, momentum distributions, two-particle correlations. • Underlying Event Studies: charged particles and energy for jet, jet+jet, g+jet, Z+jet. • Pile-Up Studies: modeling of pile-up. Some CDF-QCD Group Analyses! Rick Field - Florida/CDF Important for the LHC!

  4. Jets at 1.96 TeV “Real Jets” “Theory Jets” • Experimental Jets: The study of “real” jets requires a “jet algorithm” and the different algorithms correspond to different observables and give different results! Next-to-leading order parton level calculation 0, 1, 2, or 3 partons! • Experimental Jets: The study of “real” jets requires a good understanding of the calorimeter response! • Experimental Jets: To compare with NLO parton level (and measure structure functions) requires a good understanding of the “underlying event”! Rick Field - Florida/CDF

  5. KT Algorithm • kT Algorithm: • Cluster together calorimeter towers by their kT proximity. • Infrared and collinear safe at all orders of pQCD. • No splitting and merging. • No ad hoc Rsep parameter necessary to compare with parton level. • Every parton, particle, or tower is assigned to a “jet”. • No biases from seed towers. • Favored algorithm in e+e- annihilations! Will the KT algorithm be effective in the collider environment where there is an “underlying event”? KT Algorithm Raw Jet ET = 533 GeV Raw Jet ET = 618 GeV CDF Run 2 Only towers with ET > 0.5 GeV are shown Rick Field - Florida/CDF

  6. Jet Corrections • Calorimeter Jets: • We measure “jets” at the “hadron level” in the calorimeter. • We certainly want to correct the “jets” for the detector resolution and effieciency. • Also, we must correct the “jets” for “pile-up”. • Must correct what we measure back to the true “particle level” jets! • Particle Level Jets: • Do we want to make further model dependent corrections? • Do we want to try and subtract the “underlying event” from the “particle level” jets. • This cannot really be done, but if you trust the Monte-Carlo models modeling of the “underlying event” you can try and do it by using the Monte-Carlo models. • Parton Level Jets: • Do we want to use our data to try and extrapolate back to the parton level? • This also cannot really be done, but again if you trust the Monte-Carlo models you can try and do it by using the Monte-Carlo models. The “underlying event” consists of hard initial & final-state radiation plus the “beam-beam remnants” and possible multiple parton interactions. Rick Field - Florida/CDF

  7. Jet Corrections I believe we should correct the data back to what we measure (i.e. the particle level with an “underlying event”)! • Calorimeter Jets: • We measure “jets” at the “hadron level” in the calorimeter. • We certainly want to correct the “jets” for the detector resolution and effieciency. • Also, we must correct the “jets” for “pile-up”. • Must correct what we measure back to the true “particle level” jets! Experiment I believe we should correct (or calculate) the theory for what we measure (i.e. the particle level with an “underlying event”)! We need MC@NLO! • Particle Level Jets: • Do we want to make further model dependent corrections? • Do we want to try and subtract the “underlying event” from the “particle level” jets. • This cannot really be done, but if you trust the Monte-Carlo models modeling of the “underlying event” you can try and do it by using the Monte-Carlo models. Theory • Parton Level Jets: • Do we want to use our data to try and extrapolate back to the parton level? • This also cannot really be done, but again if you trust the Monte-Carlo models you can try and do it by using the Monte-Carlo models. The “underlying event” consists of hard initial & final-state radiation plus the “beam-beam remnants” and possible multiple parton interactions. Rick Field - Florida/CDF

  8. KT Jet Cross-Section NLO parton level theory corrected to the “particle level”! Data at the “particle level”! Correction factors applied to NLO theory! Rick Field - Florida/CDF

  9. KT Jet Cross-Section NLO parton level theory corrected to the “particle level”! Data at the “particle level”! 7 7 8 Correction factors applied to NLO theory! Rick Field - Florida/CDF

  10. KT Jet Cross-Section NLO parton level theory corrected to the “hadron level”! Data at the “hadron level”! Theory and experiment agree very well! The KT algorithm works fine at the collider! Correction factors applied to NLO theory! Rick Field - Florida/CDF

  11. The b-Jet InclusiveCross-Section Construct the invariant mass of particles pointing back to the secondary vertex! 98 < pT(jet) < 106 GeV/c Monte-Carlo Templates • Extract fraction of b-tagged jets from data using the shape of the mass of the secondary vertex as discriminating quantity (bin-by-bin as a function of jet pT). Rick Field - Florida/CDF

  12. The b-Jet InclusiveCross-Section Inclusive b-Jet Cross Section • The data are compared with PYTHIA (tune A)! Data/PYA ~ 1.4 • Comparison with MC@NLO coming soon! Rick Field - Florida/CDF

  13. The b-bbar DiJet Cross-Section • ET(b-jet#1) > 30 GeV, ET(b-jet#2) > 20 GeV, |h(b-jets)| < 1.2. Systematic Uncertainty Preliminary CDF Results: sbb = 34.5  1.8  10.5nb QCD Monte-Carlo Predictions: Differential Cross Section as a function of the b-bbar DiJet invariant mass! • Large Systematic Uncertainty: • Jet Energy Scale (~20%). • b-tagging Efficiency (~8%) Predominately Flavor creation! Rick Field - Florida/CDF

  14. “Flavor Creation” b-quark Initial - State Radiation Proton AntiProton Underlying Event Underlying Event Final - State b-quark Radiation The b-bbar DiJet Cross-Section • ET(b-jet#1) > 30 GeV, ET(b-jet#2) > 20 GeV, |h(b-jets)| < 1.2. Preliminary CDF Results: sbb = 34.5  1.8 10.5 nb QCD Monte-Carlo Predictions: Differential Cross Section as a function of the b-bbar DiJet invariant mass! JIMMY Runs with HERWIG and adds multiple parton interactions! JIMMY: MPI J. M. Butterworth J. R. Forshaw M. H. Seymour Adding multiple parton interactions (i.e. Jimmy) to enhance the “underlying event” increases the b-bbar jet cross section! Rick Field - Florida/CDF

  15. b-bbar DiJet Correlations Tune A! Differential Cross Section as a function of Df of the two b-jets! • The two b-jets are predominately “back-to-back” (i.e. “flavor creation”)! • Pythia Tune A agrees fairly well with the Df correlation! Not an accident! Rick Field - Florida/CDF

  16. “Flavor Creation” b-quark Initial - State Radiation Proton AntiProton Underlying Event Underlying Event Final - State b-quark Radiation b-bbar DiJet Correlations Tune A! • The two b-jets are predominately “back-to-back” (i.e. “flavor creation”)! Differential Cross Section as a function of Df of the two b-jets! • Pythia Tune A agrees fairly well with the Df correlation! • Agrees very well with MC@NLO + HERWIG + JIMMY! Rick Field - Florida/CDF

  17. “Flavor Creation” b-quark Initial - State Radiation Proton AntiProton Underlying Event Underlying Event Final - State b-quark Radiation b-Jet bbar-Jet Correlations The “underlying event” is important in jet (and b-jet) production at the Tevatron! Tune A! • The two b-jets are predominately “back-to-back” (i.e. “flavor creation”)! Differential Cross Section as a function of Df of the two b-jets! • Pythia Tune A agrees fairly well with the Df correlation! • Agrees very well with MC@NLO + HERWIG + JIMMY! Rick Field - Florida/CDF

  18. The “Underlying Event”in Run 2 at CDF The “underlying event” consists of hard initial & final-state radiation plus the “beam-beam remnants” and possible multiple parton interactions. • Two Classes of Events: “Leading Jet” and “Back-to-Back”. • Two “Transverse” regions: “transMAX”, “transMIN”, “transDIF”. • PTmax and PTmaxT distributions and averages. • Df Distributions: “Density” and “Associated Density”. • <pT> versus charged multiplicity: “min-bias” and the “transverse” region. • Correlations between the two “transverse” regions: “trans1” vs “trans2”. “Transverse” region is very sensitive to the “underlying event”! CDF Run 2 results: Rick Field - Florida/CDF

  19. The “Transverse” Regionsas defined by the Leading Jet Look at the charged particle density in the “transverse” region! Charged Particle Df Correlations pT > 0.5 GeV/c |h| < 1 • Look at charged particle correlations in the azimuthal angle Df relative to the leading calorimeter jet (JetClu R = 0.7, |h| < 2). • Define |Df| < 60o as “Toward”, 60o < -Df < 120o and 60o < Df < 120o as “Transverse 1” and “Transverse 2”, and |Df| > 120o as “Away”. Each of the two “transverse” regions have area DhDf = 2x60o = 4p/6. The overall “transverse” region is the sum of the two transverse regions (DhDf = 2x120o = 4p/3). “Transverse” region is very sensitive to the “underlying event”! Rick Field - Florida/CDF

  20. Tuned PYTHIA 6.206 CDF Default! PYTHIA 6.206 CTEQ5L • Plot shows the “Transverse” charged particle density versus PT(chgjet#1) compared to the QCD hard scattering predictions of two tuned versions of PYTHIA 6.206 (CTEQ5L, Set B (PARP(67)=1)and Set A (PARP(67)=4)). Run 1 Analysis Old PYTHIA default (more initial-state radiation) Old PYTHIA default (more initial-state radiation) New PYTHIA default (less initial-state radiation) New PYTHIA default (less initial-state radiation) Rick Field - Florida/CDF

  21. Run 1 b-quarkAzimuthal Correlations PYTHIA Tune A (more initial-state radiation) PYTHIA Tune B (less initial-state radiation) • Predictions of PYTHIA 6.206 (CTEQ5L) with PARP(67)=1 (new default, Tune B) and PARP(67)=4 (old default, Tune A) for the azimuthal angle, Df, between a b-quark with PT1 > 15 GeV/c, |y1| < 1 and bbar-quark with PT2 > 10 GeV/c, |y2|<1 in proton-antiproton collisions at 1.8 TeV. The curves correspond to ds/dDf (mb/o) for flavor creation, flavor excitation, shower/fragmentation, and the resulting total. Rick Field - Florida/CDF

  22. Run 1 b-quarkAzimuthal Correlations PYTHIA Tune A (more initial-state radiation) • Predictions of HERWIG 6.4 (CTEQ5L) for the azimuthal angle, Df, between a b-quark with PT1 > 15 GeV/c, |y1| < 1 and bbar-quark with PT2 > 10 GeV/c, |y2|<1 in proton-antiproton collisions at 1.8 TeV. The curves correspond to ds/dDf (mb/o) for flavor creation, flavor excitation, shower/fragmentation, and the resulting total. PYTHIA Tune B (less initial-state radiation) “Flavor Creation” Rick Field - Florida/CDF

  23. CDF Run I AnalysisAzimuthal Correlations • Run I preliminary uncorrected CDF data for the azimuthal angle, Df, between a b-quark |y1| < 1 and bbar-quark |y2|<1 in proton-antiproton collisions at 1.8 TeV. Preliminary CDF Run 1 b-bbar quark Df! • PYTHIA Tune A (with more initial state radiation) agreed better with the CDF Run 1 data! • Thus we choose Tune A over Tune B as the CDF default! Now Published! Phys. Rev. D71, 092001 (2005) Rick Field - Florida/CDF

  24. Charged Particle DensityDf Dependence Run 2 Refer to this as a “Leading Jet” event • Look at the “transverse” region as defined by the leading jet (JetClu R = 0.7, |h| < 2) or by the leading two jets (JetClu R = 0.7, |h| < 2). “Back-to-Back” events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back-to-back” (Df12 > 150o) with almost equal transverse energies (ET(jet#2)/ET(jet#1) > 0.8) and ET(jet#3) < 15 GeV. Subset Refer to this as a “Back-to-Back” event • Shows the Df dependence of the charged particle density, dNchg/dhdf, for charged particles in the range pT > 0.5 GeV/c and |h| < 1 relative to jet#1 (rotated to 270o) for 30 < ET(jet#1) < 70 GeV for “Leading Jet” and “Back-to-Back” events. Rick Field - Florida/CDF

  25. “Transverse” PTsum DensityPYTHIA Tune A vs HERWIG “Leading Jet” “Back-to-Back” Now look in detail at “back-to-back” events in the region 30 < ET(jet#1) < 70 GeV! • Shows the average charged PTsum density, dPTsum/dhdf, in the “transverse” region (pT > 0.5 GeV/c, |h| < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events. • Compares the (uncorrected) data with PYTHIA Tune A and HERWIG after CDFSIM. Rick Field - Florida/CDF

  26. Charged PTsum DensityPYTHIA Tune A vs HERWIG HERWIG (without multiple parton interactions) does not produces enough PTsum in the “transverse” region for 30 < ET(jet#1) < 70 GeV! Rick Field - Florida/CDF

  27. Tuned JIMMY versusPYTHIA Tune A JIMMY: MPI J. M. Butterworth J. R. Forshaw M. H. Seymour JIMMY Runs with HERWIG and adds multiple parton interactions! JIMMY tuned to agree with PYTHIA Tune A! • (left) Shows the Run 2 data on the Df dependence of the charged scalar PTsum density (|h|<1, pT>0.5 GeV/c) relative to the leading jet for 30 < ET(jet#1) < 70 GeV/c compared with PYTHIA Tune A (after CDFSIM). • (right) Shows the generator level predictions of PYTHIA Tune A and a tuned version of JIMMY (PTmin=1.8 GeV/c) for the Df dependence of the charged scalar PTsum density (|h|<1, pT>0.5 GeV/c) relative to the leading jet for PT(jet#1) > 30 GeV/c. The tuned JIMMY and PYTHIA Tune A agree in the “transverse” region. • (right) For JIMMY the contributions from the multiple parton interactions (MPI), initial-state radiation (ISR), and the 2-to-2 hard scattering plus finial-state radiation (2-to-2+FSR) are shown. Rick Field - Florida/CDF

  28. JIMMY (MPI) versus HERWIG (BBR) • (left) Shows the generator level predictions of JIMMY (MPI, PTmin=1.8 GeV/c) and HERWIG (BBR) for the Df dependence of the charged scalar PTsum density (|h|<1, pT>0.5 GeV/c) relative to the leading jet for PT(jet#1) > 30 GeV/c. • (right) Shows the generator level predictions of JIMMY (MPI, PTmin=1.8 GeV/c) and HERWIG (BBR) for the Df dependence of the scalar ETsum density (|h|<1, pT>0 GeV/c) relative to the leading jet for PT(jet#1) > 30 GeV/c. • The “multiple-parton interaction” (MPI) contribution from JIMMY is about a factor of two larger than the “Beam-Beam Remnant” (BBR) contribution from HERWIG. The JIMMY program replaces the HERWIG BBR is its MPI. Rick Field - Florida/CDF

  29. Tuned JIMMY versusPYTHIA Tune A Tuned JIMMY produces more ETsum than PYTHIA Tune A! • (left) Shows the generator level predictions of PYTHIA Tune A and JIMMY (PTmin=1.8 GeV/c) for the Df dependence of the charged scalar PTsum density (|h|<1, pT>0.5 GeV/c) relative to the leading jet with PT(jet#1) > 30 GeV/c. JIMMY and PYTHIA Tune A agree in the “transverse” region.. • (right) Shows the generator level predictions of PYTHIA Tune A and JIMMY (PTmin=1.8 GeV/c) for the Df dependence of the scalar ETsum density (|h|<1, pT>0) relative to the leading jet for PT(jet#1) > 30 GeV/c. • The tuned JIMMY produces a lot more ETsum (pT>0) in the “transverse” region than does PYTHIA Tune A! Rick Field - Florida/CDF

  30. Tuned JIMMY versusPYTHIA Tune A Tuned JIMMY produces more ETsum than PYTHIA Tune A! The next step is to study the energy in the “transverse region”. We will have results on this soon! • (left) Shows the generator level predictions of PYTHIA Tune A and JIMMY (PTmin=1.8 GeV/c) for the Df dependence of the charged scalar PTsum density (|h|<1, pT>0.5 GeV/c) relative to the leading jet with PT(jet#1) > 30 GeV/c. JIMMY and PYTHIA Tune A agree in the “transverse” region.. • (right) Shows the generator level predictions of PYTHIA Tune A and JIMMY (PTmin=1.8 GeV/c) for the Df dependence of the scalar ETsum density (|h|<1, pT>0) relative to the leading jet for PT(jet#1) > 30 GeV/c. • The tuned JIMMY produces a lot more ETsum (pT>0) in the “transverse” region than does PYTHIA Tune A! Rick Field - Florida/CDF

  31. “Flavor Creation” b-quark Initial - State Radiation Proton AntiProton Underlying Event Underlying Event Final - State b-quark Radiation Summary • The KT algorithm works fine at the Tevatron and theory/data (CTEQ61M) look flat! KT Algorithm • We have measured the inclusive b-jet section, b-bbar jet cross section and correlations, and everything is as expected - nothing goofy! CDF Run 2 “Underlying event” important in jet (and b-jet) production! • We are making good progress in understanding and modeling the “underlying event”. We now have PYTHIA tune A and JIMMY tune A! Energy density in the “transverse region” coming soon! Rick Field - Florida/CDF

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