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Studying the Underlying Event at CDF and the LHC

Studying the Underlying Event at CDF and the LHC. Rick Field University of Florida. Outline of Talk. Review what we learned about “min-bias” and the “underlying event” in Run 1 at CDF. LBNL January 13, 2009. Explain the various PYTHIA “underlying event” tunes and extrapolations to the LHC.

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Studying the Underlying Event at CDF and the LHC

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  1. Studying the Underlying Event atCDF and the LHC Rick Field University of Florida Outline of Talk • Review what we learned about “min-bias” and the “underlying event” in Run 1 at CDF. LBNL January 13, 2009 • Explain the various PYTHIA “underlying event” tunes and extrapolations to the LHC. • “CDF-QCD Data for Theory”: Studying the “underlying event” using high pT jet production and Z-boson production. R. Field, C. Group, & D. Kar • Some things I do not understand about the CDF “underlying event” data. • UE&MB@CMS: Plans to measure “min-bias” and the “underlying event” at CMS. CMS at the LHC CDF Run 2 Rick Field – Florida/CDF/CMS

  2. “Hard Scattering” Component QCD Monte-Carlo Models:High Transverse Momentum Jets • Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and final-state gluon radiation (in the leading log approximation or modified leading log approximation). “Underlying Event” • The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or semi-soft multiple parton interactions (MPI). The “underlying event” is an unavoidable background to most collider observables and having good understand of it leads to more precise collider measurements! • Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event” observables receive contributions from initial and final-state radiation. Rick Field – Florida/CDF/CMS

  3. “Hard Scattering” Component QCD Monte-Carlo Models:Lepton-Pair Production • Start with the perturbative Drell-Yan muon pair production and add initial-state gluon radiation (in the leading log approximation or modified leading log approximation). “Underlying Event” • The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or semi-soft multiple parton interactions (MPI). • Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event” observables receive contributions from initial-state radiation. Rick Field – Florida/CDF/CMS

  4. Proton-AntiProton Collisionsat the Tevatron The CDF “Min-Bias” trigger picks up most of the “hard core” cross-section plus a small amount of single & double diffraction. stot = sEL + sIN stot = sEL + sSD+sDD+sHC 1.8 TeV: 78mb = 18mb + 9mb + (4-7)mb + (47-44)mb CDF “Min-Bias” trigger 1 charged particle in forward BBC AND 1 charged particle in backward BBC The “hard core” component contains both “hard” and “soft” collisions. Beam-Beam Counters 3.2 < |h| < 5.9 Rick Field – Florida/CDF/CMS

  5. 3 charged particles dNchg/dhdf = 3/4p = 0.24 1 charged particle Divide by 4p 1 GeV/c PTsum dNchg/dhdf = 1/4p = 0.08 3 GeV/c PTsum dPTsum/dhdf = 1/4p GeV/c = 0.08 GeV/c dPTsum/dhdf = 3/4p GeV/c = 0.24 GeV/c Particle Densities • Study the charged particles (pT > 0.5 GeV/c, |h| < 1) and form the charged particle density, dNchg/dhdf, and the charged scalar pT sum density, dPTsum/dhdf. Charged Particles pT > 0.5 GeV/c |h| < 1 CDF Run 2 “Min-Bias” DhDf = 4p = 12.6 Rick Field – Florida/CDF/CMS

  6. CDF Run 1 “Min-Bias” DataCharged Particle Density • Shows CDF “Min-Bias” data on the number of charged particles per unit pseudo-rapidity at 630 and 1,800 GeV. There are about 4.2 charged particles per unit h in “Min-Bias” collisions at 1.8 TeV (|h| < 1, all pT). <dNchg/dh> = 4.2 <dNchg/dhdf> = 0.67 • Convert to charged particle density, dNchg/dhdf, by dividing by 2p. There are about 0.67 charged particles per unit h-f in “Min-Bias” collisions at 1.8 TeV (|h| < 1, all pT). 0.25 0.67 • There are about 0.25 charged particles per unit h-f in “Min-Bias” collisions at 1.96 TeV (|h| < 1, pT > 0.5 GeV/c). Rick Field – Florida/CDF/CMS

  7. CDF Run 2 Min-Bias “Associated”Charged Particle Density “Associated” densities do not include PTmax! Highest pT charged particle! • Use the maximum pT charged particle in the event, PTmax, to define a direction and look at the the “associated” density, dNchg/dhdf, in “min-bias” collisions (pT > 0.5 GeV/c, |h| < 1). It is more probable to find a particle accompanying PTmax than it is to find a particle in the central region! • Shows the data on the Df dependence of the “associated” charged particle density, dNchg/dhdf, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” events. Also shown is the average charged particle density, dNchg/dhdf, for “min-bias” events. Rick Field – Florida/CDF/CMS

  8. CDF Run 2 Min-Bias “Associated”Charged Particle Density Rapid rise in the particle density in the “transverse” region as PTmax increases! PTmax > 2.0 GeV/c Transverse Region Transverse Region Ave Min-Bias 0.25 per unit h-f PTmax > 0.5 GeV/c • Shows the data on the Df dependence of the “associated” charged particle density, dNchg/dhdf, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” eventswith PTmax > 0.5, 1.0, and 2.0 GeV/c. • Shows “jet structure” in “min-bias” collisions (i.e.the “birth” of the leading two jets!). Rick Field – Florida/CDF/CMS

  9. CDF Run 1: Evolution of Charged Jets“Underlying Event” • Look at charged particle correlations in the azimuthal angle Df relative to the leading charged particle jet. • Define |Df| < 60o as “Toward”, 60o < |Df| < 120o as “Transverse”, and |Df| > 120o as “Away”. • All three regions have the same size in h-f space, DhxDf = 2x120o = 4p/3. Charged Particle Df Correlations PT > 0.5 GeV/c |h| < 1 Look at the charged particle density in the “transverse” region! “Transverse” region very sensitive to the “underlying event”! CDF Run 1 Analysis Rick Field – Florida/CDF/CMS

  10. Factor of 2! Run 1 Charged Particle Density“Transverse” pT Distribution • Compares the average “transverse” charge particle density with the average “Min-Bias” charge particle density (|h|<1, pT>0.5 GeV). Shows how the “transverse” charge particle density and the Min-Bias charge particle density is distributed in pT. PT(charged jet#1) > 30 GeV/c “Transverse” <dNchg/dhdf> = 0.56 “Min-Bias” CDF Run 1 Min-Bias data <dNchg/dhdf> = 0.25 Rick Field – Florida/CDF/CMS

  11. ISAJET 7.32“Transverse” Density ISAJET uses a naïve leading-log parton shower-model which does not agree with the data! • Plot shows average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus PT(charged jet#1) compared to the QCD hard scattering predictions of ISAJET 7.32 (default parameters with PT(hard)>3 GeV/c) . • The predictions of ISAJET are divided into two categories: charged particles that arise from the break-up of the beam and target (beam-beam remnants); and charged particles that arise from the outgoing jet plus initial and final-state radiation(hard scattering component). ISAJET “Hard” Component Beam-Beam Remnants Rick Field – Florida/CDF/CMS

  12. HERWIG 6.4“Transverse” Density • Plot shows average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus PT(charged jet#1) compared to the QCD hard scattering predictions of HERWIG 5.9(default parameters with PT(hard)>3 GeV/c). • The predictions of HERWIG are divided into two categories: charged particles that arise from the break-up of the beam and target (beam-beam remnants); and charged particles that arise from the outgoing jet plus initial and final-state radiation(hard scattering component). HERWIG uses a modified leading-log parton shower-model which does agrees better with the data! HERWIG “Hard” Component Beam-Beam Remnants Rick Field – Florida/CDF/CMS

  13. HERWIG 6.4“Transverse” PT Distribution • Compares the average “transverse” charge particle density (|h|<1, pT>0.5 GeV) versus PT(charged jet#1) and the pT distribution of the “transverse” density, dNchg/dhdfdPT with the QCD hard scattering predictions of HERWIG 6.4(default parameters with PT(hard)>3 GeV/c. Shows how the “transverse” charge particle density is distributed in pT. HERWIG has the too steep of a pT dependence of the “beam-beam remnant” component of the “underlying event”! Herwig PT(chgjet#1) > 30 GeV/c “Transverse” <dNchg/dhdf> = 0.51 Herwig PT(chgjet#1) > 5 GeV/c <dNchg/dhdf> = 0.40 Rick Field – Florida/CDF/CMS

  14. MPI: Multiple PartonInteractions • PYTHIA models the “soft” component of the underlying event with color string fragmentation, but in addition includes a contribution arising from multiple parton interactions (MPI) in which one interaction is hard and the other is “semi-hard”. • The probability that a hard scattering events also contains a semi-hard multiple parton interaction can be varied but adjusting the cut-off for the MPI. • One can also adjust whether the probability of a MPI depends on the PT of the hard scattering, PT(hard) (constant cross section or varying with impact parameter). • One can adjust the color connections and flavor of the MPI (singlet or nearest neighbor, q-qbar or glue-glue). • Also, one can adjust how the probability of a MPI depends on PT(hard) (single or double Gaussian matter distribution). Rick Field – Florida/CDF/CMS

  15. Tuning PYTHIA:Multiple Parton Interaction Parameters Hard Core Determine by comparing with 630 GeV data! Affects the amount of initial-state radiation! Take E0 = 1.8 TeV Reference point at 1.8 TeV Rick Field – Florida/CDF/CMS

  16. PYTHIA 6.206 Defaults MPI constant probability scattering • Plot shows the “Transverse” charged particle density versus PT(chgjet#1) compared to the QCD hard scattering predictions of PYTHIA 6.206 (PT(hard) > 0) using the default parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L. PYTHIA default parameters Default parameters give very poor description of the “underlying event”! Note Change PARP(67) = 4.0 (< 6.138) PARP(67) = 1.0 (> 6.138) Rick Field – Florida/CDF/CMS

  17. Run 1 PYTHIA Tune A CDF Default! • 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)andSet A(PARP(67)=4)). PYTHIA 6.206 CTEQ5L 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/CMS

  18. PYTHIA Tune A Min-Bias“Soft” + ”Hard” Tuned to fit the CDF Run 1 “underlying event”! PYTHIA Tune A CDF Run 2 Default 12% of “Min-Bias” events have PT(hard) > 5 GeV/c! 1% of “Min-Bias” events have PT(hard) > 10 GeV/c! • PYTHIA regulates the perturbative 2-to-2 parton-parton cross sections with cut-off parameters which allows one to run with PT(hard) > 0. One can simulate both “hard” and “soft” collisions in one program. Lots of “hard” scattering in “Min-Bias” at the Tevatron! • The relative amount of “hard” versus “soft” depends on the cut-off and can be tuned. • This PYTHIA fit predicts that 12% of all “Min-Bias” events are a result of a hard 2-to-2 parton-parton scattering with PT(hard) > 5 GeV/c (1% with PT(hard) > 10 GeV/c)! Rick Field – Florida/CDF/CMS

  19. PYTHIA Tune ALHC Min-Bias Predictions 12% of “Min-Bias” events have PT(hard) > 10 GeV/c! LHC? • Shows the center-of-mass energy dependence of the charged particle density, dNchg/dhdfdPT, for “Min-Bias” collisions compared with PYTHIA Tune A with PT(hard) > 0. 1% of “Min-Bias” events have PT(hard) > 10 GeV/c! • PYTHIA Tune A predicts that 1% of all “Min-Bias” events at 1.8 TeV are a result of a hard 2-to-2 parton-parton scattering with PT(hard) > 10 GeV/c which increases to 12% at 14 TeV! Rick Field – Florida/CDF/CMS

  20. “Towards”, “Away”, “Transverse” Look at the charged particle density, the charged PTsum density and the ETsum density in all 3 regions! • Look at correlations in the azimuthal angle Df relative to the leading charged particle jet (|h| < 1) or the leading calorimeter jet (|h| < 2). • Define |Df| < 60o as “Toward”, 60o < |Df| < 120o as “Transverse ”, and |Df| > 120o as “Away”. Each of the three regions have area DhDf = 2×120o = 4p/3. Df Correlations relative to the leading jet Charged particles pT > 0.5 GeV/c |h| < 1 Calorimeter towers ET > 0.1 GeV |h| < 1 “Transverse” region is very sensitive to the “underlying event”! Z-Boson Direction Rick Field – Florida/CDF/CMS

  21. Event Topologies • “Leading Jet” events correspond to the leading calorimeter jet (MidPoint R = 0.7) in the region |h| < 2 with no other conditions. “Leading Jet” subset • “Inclusive 2-Jet 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 (PT(jet#2)/PT(jet#1) > 0.8) with no other conditions . “Inc2J Back-to-Back” subset “Exc2J Back-to-Back” • “Exclusive 2-Jet 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 (PT(jet#2)/PT(jet#1) > 0.8) and PT(jet#3) < 15 GeV/c. “Charged Jet” • “Leading ChgJet” events correspond to the leading charged particle jet (R = 0.7) in the region |h| < 1 with no other conditions. • “Z-Boson” events are Drell-Yan events with 70 < M(lepton-pair) < 110 GeV with no other conditions. Z-Boson Rick Field – Florida/CDF/CMS

  22. “transMAX” & “transMIN” • Define the MAX and MIN “transverse” regions (“transMAX” and “transMIN”) on an event-by-event basis with MAX (MIN) having the largest (smallest) density. Each of the two “transverse” regions have an area in h-f space of 4p/6. “transMIN” very sensitive to the “beam-beam remnants”! Z-Boson Direction Area = 4p/6 • The “transMIN” region is very sensitive to the “beam-beam remnant” and the soft multiple parton interaction components of the “underlying event”. • The difference, “transDIF” (“transMAX” minus “transMIN”), is very sensitive to the “hard scattering” component of the “underlying event” (i.e. hard initial and final-state radiation). • The overall “transverse” density is the average of the “transMAX” and “transMIN” densities. Rick Field – Florida/CDF/CMS

  23. Observables at theParticle and Detector Level “Leading Jet” “Back-to-Back” Rick Field – Florida/CDF/CMS

  24. CDF Run 1 PT(Z) Tune used by the CDF-EWK group! PYTHIA 6.2 CTEQ5L • Shows the Run 1 Z-boson pT distribution (<pT(Z)> ≈ 11.5 GeV/c) compared with PYTHIA Tune A (<pT(Z)> = 9.7 GeV/c), and PYTHIA Tune AW (<pT(Z)> = 11.7 GeV/c). UE Parameters ISR Parameters Effective Q cut-off, below which space-like showers are not evolved. Intrensic KT The Q2 = kT2 in as for space-like showers is scaled by PARP(64)! Rick Field – Florida/CDF/CMS

  25. Df Jet#1-Jet#2 Jet#1-Jet#2 Df Distribution Jet-Jet Correlations (DØ) • MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5) • L= 150 pb-1 (Phys. Rev. Lett. 94 221801 (2005)) • Data/NLO agreement good. Data/HERWIG agreement good. • Data/PYTHIA agreement good provided PARP(67) = 1.0→4.0 (i.e. like Tune A, best fit 2.5). Rick Field – Florida/CDF/CMS

  26. CDF Run 1 PT(Z) PYTHIA 6.2 CTEQ5L • Shows the Run 1 Z-boson pT distribution (<pT(Z)> ≈ 11.5 GeV/c) compared with PYTHIA Tune DW, and HERWIG. UE Parameters ISR Parameters Tune DW uses D0’s perfered value of PARP(67)! Intrensic KT Tune DW has a lower value of PARP(67) and slightly more MPI! Rick Field – Florida/CDF/CMS

  27. PYTHIA 6.2 Tunes All use LO as with L = 192 MeV! UE Parameters Uses CTEQ6L Tune A energy dependence! ISR Parameter Intrinsic KT Rick Field – Florida/CDF/CMS

  28. PYTHIA 6.2 Tunes These are “old” PYTHIA 6.2 tunes! There are new 6.4 tunes by Arthur Moraes (ATLAS) Hendrik Hoeth (MCnet) Peter Skands (Tune S0) All use LO as with L = 192 MeV! UE Parameters Tune B Tune AW Tune BW Tune A ATLAS energy dependence! ISR Parameter Tune DW Tune D6 Tune D Tune D6T Intrinsic KT Rick Field – Florida/CDF/CMS

  29. PYTHIA 6.2 Tunes All use LO as with L = 192 MeV! UE Parameters Q2 ordered showers, old MPI! ISR Parameter Intrinsic KT Rick Field – Florida/CDF/CMS

  30. JIMMY at CDF JIMMY was tuned to fit the energy density in the “transverse” region for “leading jet” events! JIMMY Runs with HERWIG and adds multiple parton interactions! PT(JIM)= 2.5 GeV/c. The Drell-Yan JIMMY Tune PTJIM = 3.6 GeV/c, JMRAD(73) = 1.8 JMRAD(91) = 1.8 The Energy in the “Underlying Event” in High PT Jet Production JIMMY: MPI J. M. Butterworth J. R. Forshaw M. H. Seymour PT(JIM)= 3.25 GeV/c. “Transverse” <Densities> vs PT(jet#1) Rick Field – Florida/CDF/CMS

  31. Overall Totals (|h| < 1) ETsum = 775 GeV! • Data at 1.96 TeV on the overall number of charged particles (pT > 0.5 GeV/c, |h| < 1) and the overall scalar pT sum of charged particles (pT > 0.5 GeV/c, |h| < 1) and the overall scalar ET sum of all particles (|h| < 1) for “leading jet” events as a function of the leading jet pT. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level).. “Leading Jet” ETsum = 330 GeV PTsum = 190 GeV/c Nchg = 30 Rick Field – Florida/CDF/CMS

  32. “Towards”, “Away”, “Transverse” • Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level). “Leading Jet” Factor of ~13 Factor of ~16 Factor of ~4.5 • Data at 1.96 TeV on the charged particle scalar pT sum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level). • Data at 1.96 TeV on the particle scalar ET sum density, dET/dhdf, for |h| < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  33. Charged Particle Density HERWIG + JIMMY Tune (PTJIM = 3.6) H. Hoeth, MPI@LHC08 • Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “Z-Boson” and “Leading Jet” events as a function of the leading jet pT or PT(Z) for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and Tune A, respectively, at the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  34. Charged PTsum Density • Data at 1.96 TeV on the charged scalar PTsum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “Z-Boson” and “Leading Jet” events as a function of the leading jet pT or PT(Z) for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and Tune A, respectively, at the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  35. The “TransMAX/MIN” Regions • Data at 1.96 TeV on the charged particle density, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “Z-Boson” and “Leading Jet” events as a function of PT(Z) or the leading jet pT for the “transMAX”, and “transMIN” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and Tune A, respectively, at the particle level (i.e. generator level). • Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT and for Z-Boson events as a function of PT(Z) for “TransDIF” =“transMAX” minus “transMIN” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  36. The “TransMAX/MIN” Regions • Data at 1.96 TeV on the charged scalar PTsum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “Z-Boson” and “Leading Jet” events as a function of PT(Z) or the leading jet pT for the “transMAX”, and “transMIN” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and Tune A, respectively, at the particle level (i.e. generator level). • Data at 1.96 TeV on the charged scalar PTsum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “leading jet” events as a function of the leading jet pT and for Z-Boson events as a function of PT(Z) for “TransDIF” =“transMAX” minus “transMIN” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  37. Charged Particle <pT> H. Hoeth, MPI@LHC08 • Data at 1.96 TeV on the charged particle average pT, with pT > 0.5 GeV/c and |h| < 1 for the “toward” region for “Z-Boson” and the “transverse” region for “Leading Jet” events as a function of the leading jet pT or PT(Z). The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and Tune A, respectively, at the particle level (i.e. generator level). The Z-Boson data are also compared with PYTHIA Tune DW, the ATLAS tune, and HERWIG (without MPI) Rick Field – Florida/CDF/CMS

  38. Z-Boson: “Towards”, Transverse”, & “TransMIN” Charge Density H. Hoeth, MPI@LHC08 • Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “Z-Boson” events as a function of PT(Z) for the “toward” and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and HERWIG (without MPI) at the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  39. Z-Boson: “Towards”, Transverse”, & “TransMIN” Charge Density H. Hoeth, MPI@LHC08 • Data at 1.96 TeV on the charged scalar PTsum density, dPT/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “Z-Boson” events as a function of PT(Z) for the “toward” and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and HERWIG (without MPI) at the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  40. DWT Z-Boson: “Towards” Region • Data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 1 for “Z-Boson” events as a function of PT(Z) for the “toward” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and HERWIG (without MPI) at the particle level (i.e. generator level). HW without MPI Rick Field – Florida/CDF/CMS

  41. DWT Z-Boson: “Towards” Region • Data at 1.96 TeV on the average pT of charged particles with pT > 0.5 GeV/c and |h| < 1 for “Z-Boson” events as a function of PT(Z) for the “toward” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune AW and HERWIG (without MPI) at the particle level (i.e. generator level). HW (without MPI) almost no change! Rick Field – Florida/CDF/CMS

  42. The “Transverse” Region • Data at 1.96 TeV on the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level). “Leading Jet” 0.4 density corresponds to 1.67 GeV in the “transverse” region! • Shows the Data - Theory for the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI). Rick Field – Florida/CDF/CMS

  43. The “TransMAX/MIN” Regions • Data at 1.96 TeV on the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transMAX” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level). “Leading Jet” • Data at 1.96 TeV on the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for the “transMIN” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level). • Data at 1.96 TeV on the scalar ET sum density, dET/dhdf, with |h| < 1 for “leading jet” events as a function of the leading jet pT for “transDIF” = “transMAX”-”transMIN. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  44. The Leading Jet Mass • Data at 1.96 TeV on the leading jet invariant mass for “leading jet” events as a function of the leading jet pT for the “transverse” region. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (i.e. generator level). “Leading Jet” Off by ~2 GeV • Shows the Data - Theory for the leading jet invariant mass for “leading jet” events as a function of the leading jet pT for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI). Rick Field – Florida/CDF/CMS

  45. Min-Bias at the LHC • “Min-Bias” is not well defined. What you see depends on what you trigger on! Every trigger produces some biases. • We have learned a lot about “Min-Bias” at the Tevatron, but we do not know what to expect at the LHC. This will depend on the Min-Bias Trigger! • We are making good progress in understanding and modeling the “underlying event”. However, we do not yet have a perfect fit to all the features of the CDF “underlying event” data! • Need to measure “Min-Bias” and the “underlying event” at the LHC as soon as possible and tune the Monte-Carlo modles and compare with CDF! Rick Field – Florida/CDF/CMS

  46. The “Underlying Event” inHigh PT Jet Production (LHC) • Charged particle density in the “Transverse” region versus PT(jet#1) at 1.96 TeV for PY Tune AW and HERWIG (without MPI). Charged particle density versus PT(jet#1) The “Underlying Event” “Underlying event” much more active at the LHC! • Charged particle density in the “Transverse” region versus PT(jet#1) at 14 TeV for PY Tune AW and HERWIG (without MPI). Rick Field – Florida/CDF/CMS

  47. Drell-Yan Production (Run 2 vs LHC) • Average Lepton-Pair transverse momentum at the Tevatron and the LHC for PYTHIA Tune DW and HERWIG (without MPI). Lepton-Pair Transverse Momentum <pT(m+m-)> is much larger at the LHC! Shapes of the pT(m+m-) distribution at the Z-boson mass. Z • Shape of the Lepton-Pair pT distribution at the Z-boson mass at the Tevatron and the LHC for PYTHIA Tune DW and HERWIG (without MPI). Rick Field – Florida/CDF/CMS

  48. The “Underlying Event” inDrell-Yan Production • Charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG (without MPI). The “Underlying Event” Charged particle density versus M(pair) HERWIG (without MPI) is much less active than PY Tune AW (with MPI)! “Underlying event” much more active at the LHC! Z Z • Charged particle density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG (without MPI). Rick Field – Florida/CDF/CMS

  49. UE&MB@CMS UE&MB@CMS • “Underlying Event” Studies: The “transverse region” in “leading Jet” and “back-to-back” charged particle jet production and the “central region” in Drell-Yan production. (requires charged tracks andmuons for Drell-Yan) Study charged particles and muons using the CMS detector at the LHC (as soon as possible)! • Min-Bias Studies: Charged particle distributions and correlations. Construct “charged particle jets” and look at “mini-jet” structure and the onset of the “underlying event”. (requires only charged tracks) • Drell-Yan Studies: Transverse momentum distribution of the lepton-pair versus the mass of the lepton-pair, <pT(pair)>, <pT2(pair)>, ds/dpT(pair) (only requires muons). Event structure for large lepton-pair pT (i.e.mm +jets, requires muons). Rick Field – Florida/CDF/CMS

  50. Summary In my RPM talk on Thursday I will show new results on <pT> versus Nchg for min-bias and Z-boson production! • It is important to produce a lot of plots (corrected to the particle level) so that the theorists can tune and improve the QCD Monte-Carlo models. If they improve the “transverse” region they might miss-up the “toward” region etc.. We need to show the whole story! • We are making good progress in understanding and modeling the “underlying event”. However, we do not yet have a perfect fit to all the features of the CDF “underlying event” data! CDF Run 2 publication. Should be out soon! • There are over 128 plots to get “blessed” and then published. So far we have only looked at average quantities. We plan to also produce distributions and flow plots CDF-QCD Data for Theory • I will construct a “CDF-QCD Data for Theory” WEBsite with the “blessed” plots together with tables of the data points and errors so that people can have access to the results . UE&MB@CMS • Need to measure “Min-Bias” and the “underlying event” at the LHC as soon as possible and tune the Monte-Carlo modles and compare with CDF! Rick Field – Florida/CDF/CMS

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