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Lake Louise Winter Institute

Lake Louise Winter Institute

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Lake Louise Winter Institute

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  1. Lake Louise Winter Institute From Feynman-Field to the LHC 25 Years! Rick Field University of Florida Chateau Lake Louise February 2010 Outline of Talk 1 • The early days of Feynman-Field Phenomenology. • Studying “min-bias” collisions and the “underlying event” in Run 1 at CDF. CDF Run 2 • Tuning the QCD Monte-Carlo model generators. UE&MB@CMS CMS at the LHC • Studying the “associated” charged particle densities in “min-bias” collisions. Rick Field – Florida/CDF/CMS

  2. Feynman-Field Phenomenology Toward and Understanding of Hadron-Hadron Collisions 1st hat! Feynman and Field • From 7 GeV/c p0’s to 600 GeV/c Jets. The early days of trying to understand and simulate hadron-hadron collisions. Rick Field – Florida/CDF/CMS

  3. Hadron-Hadron Collisions FF1 1977 • What happens when two hadrons collide at high energy? Feynman quote from FF1 “The model we shall choose is not a popular one, so that we will not duplicate too much of the work of others who are similarly analyzing various models (e.g. constituent interchange model, multiperipheral models, etc.). We shall assume that the high PT particles arise from direct hard collisions between constituent quarks in the incoming particles, which fragment or cascade down into several hadrons.” • Most of the time the hadrons ooze through each other and fall apart (i.e.no hard scattering). The outgoing particles continue in roughly the same direction as initial proton and antiproton. • Occasionally there will be a large transverse momentum meson. Question: Where did it come from? • We assumed it came from quark-quark elastic scattering, but we did not know how to calculate it! “Black-Box Model” Rick Field – Florida/CDF/CMS

  4. Quark-Quark Black-Box Model No gluons! FF1 1977 Quark Distribution Functions determined from deep-inelastic lepton-hadron collisions Feynman quote from FF1 “Because of the incomplete knowledge of our functions some things can be predicted with more certainty than others. Those experimental results that are not well predicted can be “used up” to determine these functions in greater detail to permit better predictions of further experiments. Our papers will be a bit long because we wish to discuss this interplay in detail.” Quark Fragmentation Functions determined from e+e- annihilations Quark-Quark Cross-Section Unknown! Deteremined from hadron-hadron collisions. Rick Field – Florida/CDF/CMS

  5. Quark-Quark Black-Box Model FF1 1977 Predict increase with increasing CM energy W Predict particle ratios “Beam-Beam Remnants” Predict overall event topology (FFF1 paper 1977) 7 GeV/c p0’s! Rick Field – Florida/CDF/CMS

  6. Feynman Talk at Coral Gables(December 1976) 1st transparency Last transparency “Feynman-Field Jet Model” Rick Field – Florida/CDF/CMS

  7. QCD Approach: Quarks & Gluons Quark & Gluon Fragmentation Functions Q2 dependence predicted from QCD FFF2 1978 Feynman quote from FFF2 “We investigate whether the present experimental behavior of mesons with large transverse momentum in hadron-hadron collisions is consistent with the theory of quantum-chromodynamics (QCD) with asymptotic freedom, at least as the theory is now partially understood.” Parton Distribution Functions Q2 dependence predicted from QCD Quark & Gluon Cross-Sections Calculated from QCD Rick Field – Florida/CDF/CMS

  8. (bk) (ka) (ba) (cb) cc pair bb pair A Parameterization of the Properties of Jets • Assumed that jets could be analyzed on a “recursive” principle. Field-Feynman 1978 Secondary Mesons (after decay) • Let f(h)dh be the probability that the rank 1 meson leaves fractional momentum h to the remaining cascade, leaving quark “b” with momentum P1 = h1P0. Rank 2 Rank 1 • Assume that the mesons originating from quark “b” are distributed in presisely the same way as the mesons which came from quark a (i.e. same function f(h)), leaving quark “c” with momentum P2 = h2P1 = h2h1P0. Primary Mesons continue • Add in flavor dependence by letting bu = probabliity of producing u-ubar pair, bd = probability of producing d-dbar pair, etc. Calculate F(z) from f(h) and bi! • Let F(z)dz be the probability of finding a meson (independent of rank) with fractional mementum z of the original quark “a” within the jet. Original quark with flavor “a” and momentum P0 Rick Field – Florida/CDF/CMS

  9. Feynman-Field Jet Model R. P. Feynman ISMD, Kaysersberg, France, June 12, 1977 Feynman quote from FF2 “The predictions of the model are reasonable enough physically that we expect it may be close enough to reality to be useful in designing future experiments and to serve as a reasonable approximation to compare to data. We do not think of the model as a sound physical theory, ....” Rick Field – Florida/CDF/CMS

  10. High PT Jets CDF (2006) Feynman, Field, & Fox (1978) Predict large “jet” cross-section 30 GeV/c! Feynman quote from FFF “At the time of this writing, there is still no sharp quantitative test of QCD. An important test will come in connection with the phenomena of high PT discussed here.” 600 GeV/c Jets! Rick Field – Florida/CDF/CMS

  11. CDF DiJet Event: M(jj) ≈ 1.4 TeV ETjet1 = 666 GeV ETjet2 = 633 GeV Esum = 1,299 GeV M(jj) = 1,364 GeV M(jj)/Ecm≈ 70%!! Rick Field – Florida/CDF/CMS

  12. Monte-Carlo Simulationof Hadron-Hadron Collisions FF1-FFF1 (1977) “Black-Box” Model FF2 (1978) Monte-Carlo simulation of “jets” F1-FFF2 (1978) QCD Approach FFFW “FieldJet” (1980) QCD “leading-log order” simulation of hadron-hadron collisions “FF” or “FW” Fragmentation my early days yesterday ISAJET (“FF” Fragmentation) HERWIG (“FW” Fragmentation) PYTHIA (“String” Fragmentation) today HERWIG++ PYTHIA 6.4 SHERPA Rick Field – Florida/CDF/CMS

  13. Proton-Proton Collisions stot = sEL + sSD+sDD+sHC ND “Inelastic Non-Diffractive Component” The “hard core” component contains both “hard” and “soft” collisions. Rick Field – Florida/CDF/CMS

  14. Inelastic Non-Diffractive Cross-Section • The inelastic non-diffractive cross section versus center-of-mass energy from PYTHIA (×1.2). My guess! Linear scale! Log scale! stot = sEL + sSD+sDD+sND • sHC varies slowly. Only a 13% increase between 7 TeV (≈ 58 mb) and 14 teV (≈ 66 mb). Linear on a log scale! Rick Field – Florida/CDF/CMS

  15. “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

  16. 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

  17. Proton Proton Proton Proton MPI, Pile-Up, and Overlap MPI: Multiple Parton Interactions • MPI: Additional 2-to-2 parton-parton scatterings within a single hadron-hadron collision. Pile-Up Interaction Region Dz • Pile-Up: More than one hadron-hadron collision in the beam crossing. Overlap • Overlap: An experimental timing issue where a hadron-hadron collision from the next beam crossing gets included in the hadron-hadron collision from the current beam crossing because the next crossing happened before the event could be read out. Rick Field – Florida/CDF/CMS

  18. 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

  19. 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

  20. 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

  21. Tuning PYTHIA:Multiple Parton Interaction Parameters Hard Core Determines the energy dependence of the MPI! 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

  22. “Transverse” Conesvs “Transverse” Regions • Sum the PT of charged particles in two cones of radius 0.7 at the same h as the leading jet but with |DF| = 90o. • Plot the cone with the maximum and minimum PTsum versus the ET of the leading (calorimeter) jet. “Cone Analysis” (Tano, Kovacs, Huston, Bhatti) Transverse Cone: p(0.7)2=0.49p Transverse Region: 2p/3=0.67p Rick Field – Florida/CDF/CMS

  23. Energy Dependenceof the “Underlying Event” “Cone Analysis” (Tano, Kovacs, Huston, Bhatti) • Sum the PT of charged particles (pT > 0.4 GeV/c) in two cones of radius 0.7 at the same h as the leading jet but with |DF| = 90o. Plot the cone with the maximum and minimum PTsum versus the ET of the leading (calorimeter) jet. • Note that PYTHIA 6.115 is tuned at 630 GeV with PT0 = 1.4 GeV and at 1,800 GeV with PT0 = 2.0 GeV. This implies that e = PARP(90) should be around 0.30 instead of the 0.16 (default). • For the MIN cone 0.25 GeV/c in radius R = 0.7 implies a PTsum density of dPTsum/dhdf = 0.16 GeV/c and 1.4 GeV/c in the MAX cone implies dPTsum/dhdf = 0.91 GeV/c (average PTsum density of 0.54 GeV/c per unit h-f). 630 GeV 1,800 GeV PYTHIA 6.115 PT0 = 1.4 GeV PYTHIA 6.115 PT0 = 2.0 GeV Rick Field – Florida/CDF/CMS

  24. “Transverse” Charged DensitiesEnergy Dependence Rick Field Fermilab MC Workshop October 4, 2002! Increasing e produces less energy dependence for the UE resulting in less UE activity at the LHC! Lowering PT0 at 630 GeV (i.e. increasing e) increases UE activity resulting in less energy dependence. • Shows the “transverse” charged PTsum density (|h|<1, PT>0.4 GeV) versus PT(charged jet#1) at 630 GeV predicted by HERWIG 6.4 (PT(hard) > 3 GeV/c, CTEQ5L) and a tuned version of PYTHIA 6.206 (PT(hard) > 0, CTEQ5L, Set A, e = 0, e = 0.16 (default) and e = 0.25 (preferred)). • Also shown are the PTsum densities (0.16 GeV/c and 0.54 GeV/c) determined from the Tano, Kovacs, Huston, and Bhatti “transverse” cone analysis at 630 GeV. Reference point E0 = 1.8 TeV Rick Field – Florida/CDF/CMS

  25. 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

  26. 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

  27. 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

  28. 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

  29. 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

  30. 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

  31. PYTHIA 6.2 Tunes These are “old” PYTHIA 6.2 tunes! There are new 6.420 tunes by Peter Skands (Tune S320, update of S0) Peter Skands (Tune N324, N0CR) Hendrik Hoeth (Tune P329, “Professor”) 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 CMS Rick Field – Florida/CDF/CMS

  32. Peter’s Pythia Tunes WEBsite • http://home.fnal.gov/~skands/leshouches-plots/ Rick Field – Florida/CDF/CMS

  33. “Transverse” Charged Density 0.6 • Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 1) at 1.96 TeVas defined by PTmax, PT(chgjet#1), and PT(jet#1) from PYTHIATune Aat the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  34. Min-Bias “Associated”Charged Particle Density About a factor of 2.7 increase in the “transverse” region! • Shows the “associated” charged particle density in the “toward”, “away” and “transverse” regions as a function of PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 1.96 TeV and at 0.2 TeVfrom PYTHIATune DW at the particle level (i.e. generator level). 1.96 TeV ← 0.2 TeV (~factor of 10 increase) Tevatron RHIC Rick Field – Florida/CDF/CMS

  35. Min-Bias “Associated”Charged Particle Density About a factor of 2 increase in the “transverse” region! • Shows the “associated” charged particle density in the “toward”, “away” and “transverse” regions as a function of PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 1.96 TeV and at 14 TeVfrom PYTHIATune DW at the particle level (i.e. generator level). 1.96 TeV → 14 TeV (~factor of 7 increase) Tevatron LHC Rick Field – Florida/CDF/CMS

  36. Min-Bias “Associated”Charged Particle Density 35% more at RHIC means 26% less at the LHC! • Shows the “associated” charged particle density in the “transverse” regions as a function of PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 0.2 TeV and 14 TeVfrom PYTHIA Tune DW and Tune DWT at the particle level (i.e. generator level). The STAR data from RHIC favors Tune DW! ~1.35 ~1.35 0.2 TeV → 14 TeV (~factor of 70 increase) RHIC LHC Rick Field – Florida/CDF/CMS

  37. Min-Bias “Associated”Charged Particle Density • Shows the “associated” charged particle density in the “transverse” region as a function of PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 0.2 TeV, 1.96 TeV and 14 TeVpredicted by PYTHIA Tune DW at the particle level (i.e. generator level). ~1.9 ~2.7 0.2 TeV → 1.96 TeV (UE increase ~2.7 times) 1.96 TeV → 14 TeV (UE increase ~1.9 times) RHIC LHC Tevatron Rick Field – Florida/CDF/CMS

  38. The “Underlying Event” at STAR • At STAR they have measured the “underlying event at W = 200 GeV (|h| < 1, pT > 0.2 GeV) and compared their uncorrected data with PYTHIA Tune A + STAR-SIM. Rick Field – Florida/CDF/CMS

  39. Preliminary The “Underlying Event” at STAR Charged PTsum Density “Back-to-Back” Charged Particles (|h|<1.0, PT>0.2 GeV/c) Data uncorrected PYTHIA Tune A + STAR-SIM “Toward” 0.55 “Away” ~1.5 “Transverse” 0.37 “Leading Jet” PT(jet#1) (GeV/c) “Back-to-Back” • Data on the charged particle scalar pT sum density, dPT/dhdf, as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions compared with PYTHIA Tune A. Rick Field – Florida/CDF/CMS

  40. 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

  41. 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

  42. Min-Bias “Associated”Charged Particle Density PY Tune A PTmax > 2.0 GeV/c Transverse Region Transverse Region 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 GeV/c and PTmax > 2.0 GeV/c compared with PYTHIA Tune A (after CDFSIM). • PYTHIA Tune A predicts a larger correlation than is seen in the “min-bias” data (i.e.Tune A “min-bias” is a bit too “jetty”). Rick Field – Florida/CDF/CMS

  43. Min-Bias “Associated”Charged Particle Density • Shows the “associated” charged particle density in the “toward”, “away” and “transverse” regions as a function of PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 1.96 TeVfrom PYTHIA Tune A (generator level). “Toward” Region ~ factor of 2! “Transverse” “Transverse” • Shows 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 at 1.96 TeVwith PTmax > 0.5, 1.0, 2.0, 5.0, and 10.0 GeV/c from PYTHIA Tune A (generator level). Rick Field – Florida/CDF/CMS

  44. “Associated” Charged Particle Density • Shows the Df dependence of the “associated” charged particle density, dNchg/dhdf, for charged particles (pT > 0.5 GeV/c, |h| < 2, not including PTmax) relative to PTmax at 900 GeVwith PTmax > 2.0 GeV/c from PYTHIA Tune DW,Tune DWPro, andTune S320(generator level). PY Tune DW PY Tune DWPro PY Tune S320 Rick Field – Florida/CDF/CMS

  45. Charged Particle Density dN/dhdf • Shows the Df dependence of the “associated” charged particle density, dNchg/dhdf, for charged particles (pT > 0.5 GeV/c, |h| < 2, not including PTmax) relative to PTmax (rotated to 180o) at 900 GeVwith PTmax > 2.0 GeV/c from PYTHIA Tune DW. • Shows the Df dependence of the “overall” and “associated” charged particle density, dNchg/dhdf, for charged particles (pT > 0.5 GeV/c, |h| < 2, including all particles) relative to the leading charged particle jet (Anti-KT, d = 0.5) at 900 GeVwith PTmax > 2.0 GeV/c from PYTHIA Tune DW (generator level). Rick Field – Florida/CDF/CMS

  46. Charged Particle Density dN/dhdf AntiKT d = 0.5 AntiKT d = 0.7 • Shows the Df dependence of the “overall” and “associated” charged particle density, dNchg/dhdf, for charged particles (pT > 0.5 GeV/c, |h| < 2, including all particles) relative to the leading charged particle jet (Anti-KT, d = 0.5) at 900 GeVwith PTmax > 2.0 GeV/c from PYTHIA Tune DW (generator level). Rick Field – Florida/CDF/CMS

  47. Min-Bias “Associated”Charged Particle Density • Shows the “associated” charged particle density in the “transverse” region as a function of PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 0.2 TeV, 0.9 TeV, 1.96 TeV, 7 TeV, 10 TeV, 14 TeVpredicted by PYTHIA Tune DW at the particle level (i.e. generator level). LHC14 LHC10 LHC7 Tevatron 900 GeV RHIC 0.2 TeV → 1.96 TeV (UE increase ~2.7 times) 1.96 TeV → 14 TeV (UE increase ~1.9 times) RHIC LHC Tevatron Linear scale! Rick Field – Florida/CDF/CMS

  48. Min-Bias “Associated”Charged Particle Density • Shows the “associated” charged particle density in the “transverse” region as a function of PTmax for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) for “min-bias” events at 0.2 TeV, 0.9 TeV, 1.96 TeV, 7 TeV, 10 TeV, 14 TeVpredicted by PYTHIA Tune DW at the particle level (i.e. generator level). LHC14 LHC10 LHC7 Tevatron 900 GeV RHIC 7 TeV → 14 TeV (UE increase ~20%) LHC7 LHC14 Linear on a log plot! Log scale! Rick Field – Florida/CDF/CMS

  49. Lake Louise Winter Institute Extrapolating from the Tevatron to the LHC Rick Field University of Florida Chateau Lake Louise February 2010 Outline of Talk 2 (tomorrow) • The latest “underlying event” studies at CDF for “leading Jet” and Z-boson events. Data corrected to the particle level. CDF Run 2 • Min-Bias and the “underlying event”. • Studying <pT> versus Nchg in “min-bias” collisions and in Drell-Yan. UE&MB@CMS CMS at the LHC • UE studies at 900 GeV from CMS and ATLAS coming soon! • LHC predictions! Rick Field – Florida/CDF/CMS