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

2. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 2 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). “Hard Scattering” Component “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 and final-state radiation. The “underlying event” is an unavoidable background to most collider observables and having good understand of it leads to more precise collider measurements!

3. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 3 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. “Hard Scattering” Component

4. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 4 Proton-AntiProton Collisions at the Tevatron  tot =  EL  SD   DD   HC 1.8 TeV: 78mb = 18mb + 9mb + (4-7)mb + (47-44)mb The CDF “Min-Bias” trigger picks up most of the “hard core” cross-section plus a small amount of single & double diffraction. The “hard core” component contains both “hard” and “soft” collisions. Beam-Beam Counters 3.2 < |  | < 5.9 CDF “Min-Bias” trigger 1 charged particle in forward BBC AND 1 charged particle in backward BBC  tot =  EL  IN

5. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 5 1 charged particle dN chg /d  d  = 1/4  = 0.08  Study the charged particles (p T > 0.5 GeV/c, |  | < 1) and form the charged particle density, dN chg /d  d , and the charged scalar p T sum density, dPT sum /d  d . Charged Particles p T > 0.5 GeV/c |  | < 1  = 4  = 12.6 1 GeV/c PTsum dPT sum /d  d  = 1/4  GeV/c = 0.08 GeV/cdN chg /d  d  = 3/4  = 0.24 3 charged particles dPT sum /d  d  = 3/4  GeV/c = 0.24 GeV/c 3 GeV/c PTsum CDF Run 2 “Min-Bias” Observable Average Average Density per unit  -  N chg Number of Charged Particles (p T > 0.5 GeV/c, |  | < 1) 3.17 +/- 0.310.252 +/- 0.025 PT sum (GeV/c) Scalar p T sum of Charged Particles (p T > 0.5 GeV/c, |  | < 1) 2.97 +/- 0.230.236 +/- 0.018 Divide by 4  CDF Run 2 “Min-Bias” Particle Densities

6. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 6  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  in “Min-Bias” collisions at 1.8 TeV (|  | < 1, all p T ). = 4.2 = 0.67  Convert to charged particle density, dN chg /d  d  by dividing by 2 . There are about 0.67 charged particles per unit  -  in “Min-Bias” collisions at 1.8 TeV (|  | < 1, all p T ). 0.67  There are about 0.25 charged particles per unit  -  in “Min-Bias” collisions at 1.96 TeV (|  | 0.5 GeV/c). 0.25 CDF Run 1 “Min-Bias” Data Charged Particle Density

7. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 7  Use the maximum p T charged particle in the event, PTmax, to define a direction and look at the the “associated” density, dN chg /d  d , in “min-bias” collisions (p T > 0.5 GeV/c, |  | < 1). “Associated” densities do not include PTmax! Highest p T charged particle!  Shows the data on the  dependence of the “associated” charged particle density, dN chg /d  d , for charged particles (p T > 0.5 GeV/c, |  | < 1, not including PTmax) relative to PTmax (rotated to 180 o ) for “min-bias” events. Also shown is the average charged particle density, dN chg /d  d , for “min-bias” events. It is more probable to find a particle accompanying PTmax than it is to find a particle in the central region! CDF Run 2 Min-Bias “Associated” Charged Particle Density

8. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 8  Shows the data on the  dependence of the “associated” charged particle density, dN chg /d  d , for charged particles (p T > 0.5 GeV/c, |  | 0.5, 1.0, and 2.0 GeV/c. Transverse Region  Shows “jet structure” in “min-bias” collisions (i.e. the “birth” of the leading two jets!). Ave Min-Bias 0.25 per unit  -  PTmax > 0.5 GeV/c PTmax > 2.0 GeV/c CDF Run 2 Min-Bias “Associated” Charged Particle Density Rapid rise in the particle density in the “transverse” region as PTmax increases!

9. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 9  Look at charged particle correlations in the azimuthal angle  relative to the leading charged particle jet.  Define |  | 120 o as “Away”.  All three regions have the same size in  -  space,  x  = 2x120 o = 4  /3. Charged Particle  Correlations P T > 0.5 GeV/c |  | < 1 Look at the charged particle density in the “transverse” region! “Transverse” region very sensitive to the “underlying event”! CDF Run 1 Analysis CDF Run 1: Evolution of Charged Jets “Underlying Event”

10. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 10  Compares the average “transverse” charge particle density with the average “Min-Bias” charge particle density (|  | 0.5 GeV). Shows how the “transverse” charge particle density and the Min-Bias charge particle density is distributed in p T. CDF Run 1 Min-Bias data = 0.25 P T (charged jet#1) > 30 GeV/c “Transverse” = 0.56 Factor of 2! “Min-Bias” Run 1 Charged Particle Density “Transverse” p T Distribution

11. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 11  Plot shows average “transverse” charge particle density (|  | 0.5 GeV) versus P T (charged jet#1) compared to the QCD hard scattering predictions of ISAJET 7.32 (default parameters with P T (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). Beam-Beam Remnants ISAJET “Hard” Component ISAJET 7.32 “Transverse” Density ISAJET uses a naïve leading-log parton shower-model which does not agree with the data!

12. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 12  Plot shows average “transverse” charge particle density (|  | 0.5 GeV) versus P T (charged jet#1) compared to the QCD hard scattering predictions of HERWIG 5.9 (default parameters with P T (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). Beam-Beam Remnants HERWIG “Hard” Component HERWIG uses a modified leading- log parton shower-model which does agrees better with the data! HERWIG 6.4 “Transverse” Density

13. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 13 Herwig P T (chgjet#1) > 5 GeV/c = 0.40 Herwig P T (chgjet#1) > 30 GeV/c “Transverse” = 0.51  Compares the average “transverse” charge particle density (|  | 0.5 GeV) versus P T (charged jet#1) and the p T distribution of the “transverse” density, dN chg /d  d  dP T with the QCD hard scattering predictions of HERWIG 6.4 (default parameters with P T (hard)>3 GeV/c. Shows how the “transverse” charge particle density is distributed in p T. HERWIG has the too steep of a p T dependence of the “beam-beam remnant” component of the “underlying event”! HERWIG 6.4 “Transverse” P T Distribution

14. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 14 MPI: Multiple Parton Interactions  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 P T of the hard scattering, P T (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 P T (hard) (single or double Gaussian matter distribution).

15. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 15 ParameterDefaultDescription PARP(83)0.5Double-Gaussian: Fraction of total hadronic matter within PARP(84) PARP(84)0.2Double-Gaussian: Fraction of the overall hadron radius containing the fraction PARP(83) of the total hadronic matter. PARP(85)0.33Probability that the MPI produces two gluons with color connections to the “nearest neighbors. PARP(86)0.66Probability that the MPI produces two gluons either as described by PARP(85) or as a closed gluon loop. The remaining fraction consists of quark-antiquark pairs. PARP(89)1 TeVDetermines the reference energy E 0. PARP(90)0.16Determines the energy dependence of the cut-off P T0 as follows P T0 (E cm ) = P T0 (E cm /E 0 )  with  = PARP(90) PARP(67)1.0A scale factor that determines the maximum parton virtuality for space-like showers. The larger the value of PARP(67) the more initial- state radiation. Hard Core Take E 0 = 1.8 TeV Reference point at 1.8 TeV Determine by comparing with 630 GeV data! Affects the amount of initial-state radiation! Tuning PYTHIA: Multiple Parton Interaction Parameters

16. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 16 Default parameters give very poor description of the “underlying event”! Note Change PARP(67) = 4.0 (< 6.138) PARP(67) = 1.0 (> 6.138) Parameter6.1156.1256.1586.206 MSTP(81)1111 MSTP(82)1111 PARP(81)1.41.9 PARP(82)1.552.1 1.9 PARP(89)1,000 PARP(90)0.16 PARP(67)4.0 1.0  Plot shows the “Transverse” charged particle density versus P T (chgjet#1) compared to the QCD hard scattering predictions of PYTHIA 6.206 (P T (hard) > 0) using the default parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L. PYTHIA default parameters PYTHIA 6.206 Defaults MPI constant probability scattering

17. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 17 Old PYTHIA default (more initial-state radiation) New PYTHIA default (less initial-state radiation) ParameterTune BTune A MSTP(81)11 MSTP(82)44 PARP(82)1.9 GeV2.0 GeV PARP(83)0.5 PARP(84)0.4 PARP(85)1.00.9 PARP(86)1.00.95 PARP(89)1.8 TeV PARP(90)0.25 PARP(67)1.04.0 Old PYTHIA default (more initial-state radiation) New PYTHIA default (less initial-state radiation)  Plot shows the “transverse” charged particle density versus P T (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 Run 1 PYTHIA Tune A PYTHIA 6.206 CTEQ5L CDF Default!

18. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 18 PYTHIA Tune A Min-Bias “Soft” + ”Hard”  PYTHIA regulates the perturbative 2-to-2 parton-parton cross sections with cut-off parameters which allows one to run with P T (hard) > 0. One can simulate both “hard” and “soft” collisions in one program.  The relative amount of “hard” versus “soft” depends on the cut-off and can be tuned. Tuned to fit the CDF Run 1 “underlying event”! 12% of “Min-Bias” events have P T (hard) > 5 GeV/c! 1% of “Min-Bias” events have P T (hard) > 10 GeV/c!  This PYTHIA fit predicts that 12% of all “Min-Bias” events are a result of a hard 2-to-2 parton-parton scattering with P T (hard) > 5 GeV/c (1% with P T (hard) > 10 GeV/c)! Lots of “hard” scattering in “Min-Bias” at the Tevatron! PYTHIA Tune A CDF Run 2 Default

19. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 19  Shows the center-of-mass energy dependence of the charged particle density, dN chg /d  d  dP T, for “Min-Bias” collisions compared with PYTHIA Tune A with P T (hard) > 0.  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 P T (hard) > 10 GeV/c which increases to 12% at 14 TeV! 1% of “Min-Bias” events have P T (hard) > 10 GeV/c! 12% of “Min-Bias” events have P T (hard) > 10 GeV/c! LHC? PYTHIA Tune A LHC Min-Bias Predictions

20. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 20 “Towards”, “Away”, “Transverse”  Look at correlations in the azimuthal angle  relative to the leading charged particle jet (|  | < 1) or the leading calorimeter jet (|  | < 2).  Define |  | 120 o as “Away”. Each of the three regions have area  = 2×120 o = 4  /3.  Correlations relative to the leading jet Charged particles p T > 0.5 GeV/c |  | < 1 Calorimeter towers E T > 0.1 GeV |  | < 1 “Transverse” region is very sensitive to the “underlying event”! Look at the charged particle density, the charged PTsum density and the ETsum density in all 3 regions! Z-Boson Direction

21. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 21 Event Topologies  “Leading Jet” events correspond to the leading calorimeter jet (MidPoint R = 0.7) in the region |  | < 2 with no other conditions. “Leading Jet”  “Leading ChgJet” events correspond to the leading charged particle jet (R = 0.7) in the region |  | < 1 with no other conditions. “Charged Jet” “Inc2J Back-to-Back” “Exc2J Back-to-Back”  “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” (  12 > 150 o ) with almost equal transverse energies (P T (jet#2)/P T (jet#1) > 0.8) with no other conditions.  “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” (  12 > 150 o ) with almost equal transverse energies (P T (jet#2)/P T (jet#1) > 0.8) and P T (jet#3) < 15 GeV/c. subset Z-Boson  “Z-Boson” events are Drell-Yan events with 70 < M(lepton-pair) < 110 GeV with no other conditions.

22. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 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  -  space of 4  /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). Area = 4  /6 “transMIN” very sensitive to the “beam-beam remnants”!  The overall “transverse” density is the average of the “transMAX” and “transMIN” densities. Z-Boson Direction

23. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 23 “Back-to-Back” ObservableParticle LevelDetector Level dN chg /d  d  Number of charged particles per unit  -  (p T > 0.5 GeV/c, |  | < 1) Number of “good” charged tracks per unit  -  (p T > 0.5 GeV/c, |  | < 1) dPT sum /d  d  Scalar p T sum of charged particles per unit  -  (p T > 0.5 GeV/c, |  | < 1) Scalar p T sum of “good” charged tracks per unit  -  (p T > 0.5 GeV/c, |  | < 1) Average p T of charged particles (p T > 0.5 GeV/c, |  | < 1) Average p T of “good” charged tracks (p T > 0.5 GeV/c, |  | < 1) PT max Maximum p T charged particle (p T > 0.5 GeV/c, |  | < 1) Require Nchg ≥ 1 Maximum p T “good” charged tracks (p T > 0.5 GeV/c, |  | < 1) Require Nchg ≥ 1 dET sum /d  d  Scalar E T sum of all particles per unit  -  (all p T, |  | < 1) Scalar E T sum of all calorimeter towers per unit  -  (E T > 0.1 GeV, |  | < 1) PT sum /ET sum Scalar p T sum of charged particles (p T > 0.5 GeV/c, |  | < 1) divided by the scalar E T sum of all particles (all p T, |  | < 1) Scalar p T sum of “good” charged tracks (p T > 0.5 GeV/c, |  | < 1) divided by the scalar E T sum of calorimeter towers (E T > 0.1 GeV, |  | < 1) “Leading Jet” Observables at the Particle and Detector Level

24. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 24 CDF Run 1 P T (Z)  Shows the Run 1 Z-boson p T distribution ( ≈ 11.5 GeV/c) compared with PYTHIA Tune A ( = 9.7 GeV/c), and PYTHIA Tune AW ( = 11.7 GeV/c). ParameterTune ATune AW MSTP(81)11 MSTP(82)44 PARP(82)2.0 GeV PARP(83)0.5 PARP(84)0.4 PARP(85)0.9 PARP(86)0.95 PARP(89)1.8 TeV PARP(90)0.25 PARP(62)1.01.25 PARP(64)1.00.2 PARP(67)4.0 MSTP(91)11 PARP(91)1.02.1 PARP(93)5.015.0 The Q 2 = k T 2 in  s for space-like showers is scaled by PARP(64)! Effective Q cut-off, below which space-like showers are not evolved. UE Parameters ISR Parameters Intrensic KT PYTHIA 6.2 CTEQ5L Tune used by the CDF-EWK group!

25. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 25 Jet-Jet Correlations (DØ) Jet#1-Jet#2  Distribution  Jet#1-Jet#2  MidPoint Cone Algorithm (R = 0.7, f merge = 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).

26. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 26 CDF Run 1 P T (Z)  Shows the Run 1 Z-boson p T distribution ( ≈ 11.5 GeV/c) compared with PYTHIA Tune DW, and HERWIG. ParameterTune DWTune AW MSTP(81)11 MSTP(82)44 PARP(82)1.9 GeV2.0 GeV PARP(83)0.5 PARP(84)0.4 PARP(85)1.00.9 PARP(86)1.00.95 PARP(89)1.8 TeV PARP(90)0.25 PARP(62)1.25 PARP(64)0.2 PARP(67)2.54.0 MSTP(91)11 PARP(91)2.1 PARP(93)15.0 UE Parameters ISR Parameters Intrensic KT PYTHIA 6.2 CTEQ5L Tune DW has a lower value of PARP(67) and slightly more MPI! Tune DW uses D0’s perfered value of PARP(67)!

27. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 27 PYTHIA 6.2 Tunes ParameterTune AWTune DWTune D6 PDFCTEQ5L CTEQ6L MSTP(81)111 MSTP(82)444 PARP(82)2.0 GeV1.9 GeV1.8 GeV PARP(83)0.5 PARP(84)0.4 PARP(85)0.91.0 PARP(86)0.951.0 PARP(89)1.8 TeV PARP(90)0.25 PARP(62)1.25 PARP(64)0.2 PARP(67)4.02.5 MSTP(91)111 PARP(91)2.1 PARP(93)15.0 Intrinsic KT ISR Parameter UE Parameters Uses CTEQ6L All use LO  s with  = 192 MeV! Tune A energy dependence!

28. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 28 PYTHIA 6.2 Tunes ParameterTune DWTTune D6TATLAS PDFCTEQ5LCTEQ6LCTEQ5L MSTP(81)111 MSTP(82)444 PARP(82)1.9409 GeV1.8387 GeV1.8 GeV PARP(83)0.5 PARP(84)0.4 0.5 PARP(85)1.0 0.33 PARP(86)1.0 0.66 PARP(89)1.96 TeV 1.0 TeV PARP(90)0.16 PARP(62)1.25 1.0 PARP(64)0.2 1.0 PARP(67)2.5 1.0 MSTP(91)111 PARP(91)2.1 1.0 PARP(93)15.0 5.0 Intrinsic KT ISR Parameter UE Parameters All use LO  s with  = 192 MeV! ATLAS energy dependence! Tune A Tune AW Tune B Tune BW Tune D Tune DW Tune D6 Tune D6T These are “old” PYTHIA 6.2 tunes! There are new 6.4 tunes by Arthur Moraes (ATLAS) Hendrik Hoeth (MCnet) Peter Skands (Tune S0)

29. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 29 PYTHIA 6.2 Tunes ParameterTune H(6.418)Tune DWTTune D6TATLAS PDFCTEQ5L CTEQ6LCTEQ5L MSTP(81)1111 MSTP(82)4444 PARP(82)2.1 GeV1.9409 GeV1.8387 GeV1.8 GeV PARP(83)0.840.5 PARP(84)0.50.4 0.5 PARP(85)0.821.0 0.33 PARP(86)0.911.0 0.66 PARP(89)1.01.96 TeV 1.0 TeV PARP(90)0.170.16 PARP(62)2.971.25 1.0 PARP(64)0.120.2 1.0 PARP(67)2.742.5 1.0 MSTP(91)1111 PARP(91)2.02.1 1.0 PARP(93)5.015.0 5.0 Intrinsic KT ISR Parameter UE Parameters All use LO  s with  = 192 MeV! Q 2 ordered showers, old MPI!

30. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 30 JIMMY at CDF The Energy in the “Underlying Event” in High P T Jet Production “Transverse” vs P T (jet#1) JIMMY: MPI J. M. Butterworth J. R. Forshaw M. H. Seymour 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. PT(JIM)= 3.25 GeV/c. The Drell-Yan JIMMY Tune PTJIM = 3.6 GeV/c, JMRAD(73) = 1.8 JMRAD(91) = 1.8

31. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 31 “Leading Jet” Overall Totals (|  | < 1)  Data at 1.96 TeV on the overall number of charged particles (p T > 0.5 GeV/c, |  | 0.5 GeV/c, |  | < 1) and the overall scalar ET sum of all particles (|  | < 1) for “leading jet” events as a function of the leading jet p T. 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).. Nchg = 30 PTsum = 190 GeV/c ETsum = 330 GeV ETsum = 775 GeV!

32. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 32 “Leading Jet” “Towards”, “Away”, “Transverse”  Data at 1.96 TeV on the density of charged particles, dN/d  d , with p T > 0.5 GeV/c and |  | < 1 for “leading jet” events as a function of the leading jet p T 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 charged particle scalar p T sum density, dPT/d  d , with p T > 0.5 GeV/c and |  | < 1 for “leading jet” events as a function of the leading jet p T 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 E T sum density, dET/d  d , for |  | < 1 for “leading jet” events as a function of the leading jet p T 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). Factor of ~4.5 Factor of ~16 Factor of ~13

33. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 33 Charged Particle Density  Data at 1.96 TeV on the density of charged particles, dN/d  d , with p T > 0.5 GeV/c and |  | < 1 for “Z-Boson” and “Leading Jet” events as a function of the leading jet p T or P T (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). HERWIG + JIMMY Tune (PTJIM = 3.6) H. Hoeth, MPI@LHC08

34. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 34 Charged PTsum Density  Data at 1.96 TeV on the charged scalar PTsum density, dPT/d  d , with p T > 0.5 GeV/c and |  | < 1 for “Z- Boson” and “Leading Jet” events as a function of the leading jet p T or P T (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).

35. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 35 The “TransMAX/MIN” Regions  Data at 1.96 TeV on the charged particle density, dN/d  d , with p T > 0.5 GeV/c and |  | < 1 for “Z-Boson” and “Leading Jet” events as a function of P T (Z) or the leading jet p T 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/d  d , with p T > 0.5 GeV/c and |  | < 1 for “leading jet” events as a function of the leading jet p T and for Z-Boson events as a function of P T (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).

36. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 36 The “TransMAX/MIN” Regions  Data at 1.96 TeV on the charged scalar PTsum density, dPT/d  d , with p T > 0.5 GeV/c and |  | < 1 for “Z- Boson” and “Leading Jet” events as a function of P T (Z) or the leading jet p T 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/d  d , with p T > 0.5 GeV/c and |  | < 1 for “leading jet” events as a function of the leading jet p T and for Z-Boson events as a function of P T (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).

37. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 37 Charged Particle Charged Particle  Data at 1.96 TeV on the charged particle average p T, with p T > 0.5 GeV/c and |  | < 1 for the “toward” region for “Z-Boson” and the “transverse” region for “Leading Jet” events as a function of the leading jet p T or P T (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) H. Hoeth, MPI@LHC08

38. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 38 Z-Boson: “Towards”, Transverse”, & “TransMIN” Charge Density  Data at 1.96 TeV on the density of charged particles, dN/d  d , with p T > 0.5 GeV/c and |  | < 1 for “Z- Boson” events as a function of P T (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). H. Hoeth, MPI@LHC08

39. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 39 Z-Boson: “Towards”, Transverse”, & “TransMIN” Charge Density  Data at 1.96 TeV on the charged scalar PTsum density, dPT/d  d , with p T > 0.5 GeV/c and |  | < 1 for “Z-Boson” events as a function of P T (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). H. Hoeth, MPI@LHC08

40. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 40 Z-Boson: “Towards” Region  Data at 1.96 TeV on the density of charged particles, dN/d  d , with p T > 0.5 GeV/c and |  | < 1 for “Z- Boson” events as a function of P T (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 DWT

41. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 41 Z-Boson: “Towards” Region  Data at 1.96 TeV on the average p T of charged particles with p T > 0.5 GeV/c and |  | < 1 for “Z- Boson” events as a function of P T (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). DWT HW (without MPI) almost no change!

42. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 42 “Leading Jet” The “Transverse” Region  Data at 1.96 TeV on the scalar E T sum density, dET/d  d , with |  | < 1 for “leading jet” events as a function of the leading jet p T 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).  Shows the Data - Theory for the scalar E T sum density, dET/d  d , with |  | < 1 for “leading jet” events as a function of the leading jet p T for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI). 0.4 density corresponds to 1.67 GeV in the “transverse” region!

43. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 43 “Leading Jet” The “TransMAX/MIN” Regions  Data at 1.96 TeV on the scalar E T sum density, dET/d  d , with |  | < 1 for “leading jet” events as a function of the leading jet p T 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).  Data at 1.96 TeV on the scalar E T sum density, dET/d  d , with |  | < 1 for “leading jet” events as a function of the leading jet p T 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 E T sum density, dET/d  d , with |  | < 1 for “leading jet” events as a function of the leading jet p T 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).

44. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 44 “Leading Jet” 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 p T 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).  Shows the Data - Theory for the leading jet invariant mass for “leading jet” events as a function of the leading jet p T for the “transverse” region for PYTHIA Tune A and HERWIG (without MPI). Off by ~2 GeV

45. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 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!

46. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 46 The “Underlying Event” in High P T Jet Production (LHC)  Charged particle density in the “Transverse” region versus P T (jet#1) at 1.96 TeV for PY Tune AW and HERWIG (without MPI).  Charged particle density in the “Transverse” region versus P T (jet#1) at 14 TeV for PY Tune AW and HERWIG (without MPI). The “Underlying Event” Charged particle density versus P T (jet#1) “Underlying event” much more active at the LHC!

47. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 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 ).  Shape of the Lepton-Pair p T distribution at the Z-boson mass at the Tevatron and the LHC for PYTHIA Tune DW and HERWIG ( without MPI ). Lepton-Pair Transverse Momentum Shapes of the p T (  +  - ) distribution at the Z-boson mass. is much larger at the LHC! Z

48. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 48 The “Underlying Event” in Drell-Yan Production  Charged particle density versus the lepton- pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG ( without MPI ).  Charged particle density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG ( without MPI ). The “Underlying Event” Charged particle density versus M(pair) “Underlying event” much more active at the LHC! HERWIG (without MPI) is much less active than PY Tune AW (with MPI)! Z Z

49. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 49 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 and muons for Drell- Yan)  Drell-Yan Studies: Transverse momentum distribution of the lepton-pair versus the mass of the lepton-pair,,, d  /dp T (pair) (only requires muons). Event structure for large lepton-pair p T (i.e.  +jets, requires muons).  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) UE&MB@CMS Study charged particles and muons using the CMS detector at the LHC (as soon as possible)!

50. University of California, Berkeley January 13, 2009 Rick Field – Florida/CDF/CMSPage 50 Summary  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!  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  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!  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 CDF-QCD Data for Theory CDF Run 2 publication. Should be out soon! In my RPM talk on Thursday I will show new results on versus Nchg for min-bias and Z-boson production!