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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. CMS at the LHC Studying the “associated” charged particle densities in “min-bias” collisions. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Toward and Understanding of Hadron-Hadron Collisions
Feynman-Field Phenomenology 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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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” Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Quark-Quark Black-Box Model
FF1 1977 Predict particle ratios Predict increase with increasing CM energy W “Beam-Beam Remnants” Predict overall event topology (FFF1 paper 1977) 7 GeV/c p0’s! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Feynman Talk at Coral Gables (December 1976)
1st transparency Last transparency “Feynman-Field Jet Model” Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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 Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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A Parameterization of the Properties of Jets
Field-Feynman 1978 Secondary Mesons (after decay) Assumed that jets could be analyzed on a “recursive” principle. (bk) (ka) 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 (cb) (ba) cc pair bb pair 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 Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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, ....” Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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High PT Jets CDF (2006) Feynman, Field, & Fox (1978) 30 GeV/c! 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! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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%!! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Monte-Carlo Simulation of 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 SHERPA PYTHIA 6.4 HERWIG++ Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Proton-Proton Collisions
stot = sEL + sSD + sDD + sHC ND “Inelastic Non-Diffractive Component” The “hard core” component contains both “hard” and “soft” collisions. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Inelastic Non-Diffractive Cross-Section
My guess! Linear scale! Log scale! stot = sEL + sSD + sDD + sND The inelastic non-diffractive cross section versus center-of-mass energy from PYTHIA (×1.2). sHC varies slowly. Only a 13% increase between 7 TeV (≈ 58 mb) and 14 teV (≈ 66 mb). Linear on a log scale! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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QCD Monte-Carlo Models: High Transverse Momentum Jets
“Hard Scattering” Component “Underlying Event” 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). 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! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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 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). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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 Proton Proton Proton Proton 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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Particle Densities Charged Particles pT > 0.5 GeV/c |h| < 1
DhDf = 4p = 12.6 CDF Run 2 “Min-Bias” CDF Run 2 “Min-Bias” Observable Average Average Density per unit h-f Nchg Number of Charged Particles (pT > 0.5 GeV/c, |h| < 1) 3.17 +/- 0.31 / PTsum (GeV/c) Scalar pT sum of Charged Particles 2.97 +/- 0.23 / 1 charged particle dNchg/dhdf = 1/4p = 0.08 dNchg/dhdf = 3/4p = 0.24 3 charged particles 1 GeV/c PTsum dPTsum/dhdf = 1/4p GeV/c = 0.08 GeV/c dPTsum/dhdf = 3/4p GeV/c = 0.24 GeV/c 3 GeV/c PTsum Divide by 4p 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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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CDF Run 1: Evolution of Charged Jets “Underlying Event”
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 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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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PYTHIA default parameters
PYTHIA Defaults MPI constant probability scattering PYTHIA default parameters Parameter 6.115 6.125 6.158 6.206 MSTP(81) 1 MSTP(82) PARP(81) 1.4 1.9 PARP(82) 1.55 2.1 PARP(89) 1,000 PARP(90) 0.16 PARP(67) 4.0 1.0 Plot shows the “Transverse” charged particle density versus PT(chgjet#1) compared to the QCD hard scattering predictions of PYTHIA (PT(hard) > 0) using the default parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L. Default parameters give very poor description of the “underlying event”! Note Change PARP(67) = 4.0 (< 6.138) PARP(67) = 1.0 (> 6.138) Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Tuning PYTHIA: Multiple Parton Interaction Parameters
Default Description PARP(83) 0.5 Double-Gaussian: Fraction of total hadronic matter within PARP(84) PARP(84) 0.2 Double-Gaussian: Fraction of the overall hadron radius containing the fraction PARP(83) of the total hadronic matter. PARP(85) 0.33 Probability that the MPI produces two gluons with color connections to the “nearest neighbors. PARP(86) 0.66 Probability 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 TeV Determines the reference energy E0. PARP(82) 1.9 GeV/c The cut-off PT0 that regulates the 2-to-2 scattering divergence 1/PT4→1/(PT2+PT02)2 PARP(90) 0.16 Determines the energy dependence of the cut-off PT0 as follows PT0(Ecm) = PT0(Ecm/E0)e with e = PARP(90) PARP(67) 1.0 A 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 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 Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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“Transverse” Cones vs “Transverse” Regions
“Cone Analysis” (Tano, Kovacs, Huston, Bhatti) Transverse Cone: p(0.7)2=0.49p Transverse Region: 2p/3=0.67p 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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Energy Dependence of the “Underlying Event”
“Cone Analysis” (Tano, Kovacs, Huston, Bhatti) 630 GeV 1,800 GeV PYTHIA 6.115 PT0 = 1.4 GeV PYTHIA 6.115 PT0 = 2.0 GeV 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 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). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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“Transverse” Charged Densities Energy 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 (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 Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Run 1 PYTHIA Tune A PYTHIA 6.206 CTEQ5L
CDF Default! PYTHIA CTEQ5L Parameter Tune B Tune A MSTP(81) 1 MSTP(82) 4 PARP(82) 1.9 GeV 2.0 GeV PARP(83) 0.5 PARP(84) 0.4 PARP(85) 1.0 0.9 PARP(86) 0.95 PARP(89) 1.8 TeV PARP(90) 0.25 PARP(67) 4.0 Run 1 Analysis Plot shows the “transverse” charged particle density versus PT(chgjet#1) compared to the QCD hard scattering predictions of two tuned versions of PYTHIA (CTEQ5L, Set B (PARP(67)=1) and Set A (PARP(67)=4)). 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) Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Run 1 Charged Particle Density “Transverse” pT Distribution
Factor of 2! PT(charged jet#1) > 30 GeV/c “Transverse” <dNchg/dhdf> = 0.56 “Min-Bias” CDF Run 1 Min-Bias data <dNchg/dhdf> = 0.25 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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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CDF Run 1 PT(Z) PYTHIA 6.2 CTEQ5L
Tune used by the CDF-EWK group! PYTHIA 6.2 CTEQ5L Parameter Tune A Tune AW MSTP(81) 1 MSTP(82) 4 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) 1.0 1.25 PARP(64) 0.2 PARP(67) 4.0 MSTP(91) PARP(91) 2.1 PARP(93) 5.0 15.0 UE Parameters ISR Parameters 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). 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)! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Jet-Jet Correlations (DØ)
Df Jet#1-Jet#2 Jet#1-Jet#2 Df Distribution MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5) L = 150 pb-1 (Phys. Rev. Lett (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). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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CDF Run 1 PT(Z) PYTHIA 6.2 CTEQ5L
Parameter Tune DW Tune AW MSTP(81) 1 MSTP(82) 4 PARP(82) 1.9 GeV 2.0 GeV PARP(83) 0.5 PARP(84) 0.4 PARP(85) 1.0 0.9 PARP(86) 0.95 PARP(89) 1.8 TeV PARP(90) 0.25 PARP(62) 1.25 PARP(64) 0.2 PARP(67) 2.5 4.0 MSTP(91) PARP(91) 2.1 PARP(93) 15.0 UE Parameters ISR Parameters Shows the Run 1 Z-boson pT distribution (<pT(Z)> ≈ 11.5 GeV/c) compared with PYTHIA Tune DW, and HERWIG. 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! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Tune A energy dependence!
PYTHIA 6.2 Tunes All use LO as with L = 192 MeV! Parameter Tune AW Tune DW Tune D6 PDF CTEQ5L CTEQ6L MSTP(81) 1 MSTP(82) 4 PARP(82) 2.0 GeV 1.9 GeV 1.8 GeV PARP(83) 0.5 PARP(84) 0.4 PARP(85) 0.9 1.0 PARP(86) 0.95 PARP(89) 1.8 TeV PARP(90) 0.25 PARP(62) 1.25 PARP(64) 0.2 PARP(67) 4.0 2.5 MSTP(91) PARP(91) 2.1 PARP(93) 15.0 UE Parameters Uses CTEQ6L Tune A energy dependence! ISR Parameter Intrinsic KT Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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PYTHIA 6.2 Tunes These are “old” PYTHIA 6.2 tunes!
There are new 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! Parameter Tune DWT Tune D6T ATLAS PDF CTEQ5L CTEQ6L MSTP(81) 1 MSTP(82) 4 PARP(82) GeV GeV 1.8 GeV PARP(83) 0.5 PARP(84) 0.4 PARP(85) 1.0 0.33 PARP(86) 0.66 PARP(89) 1.96 TeV 1.0 TeV PARP(90) 0.16 PARP(62) 1.25 PARP(64) 0.2 PARP(67) 2.5 MSTP(91) PARP(91) 2.1 PARP(93) 15.0 5.0 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 Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Peter’s Pythia Tunes WEBsite
Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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“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 TeV as defined by PTmax, PT(chgjet#1), and PT(jet#1) from PYTHIA Tune A at the particle level (i.e. generator level). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Min-Bias “Associated” Charged Particle Density
About a factor of 2.7 increase in the “transverse” region! 1.96 TeV ← 0.2 TeV (~factor of 10 increase) Tevatron RHIC 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 TeV from PYTHIA Tune DW at the particle level (i.e. generator level). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Min-Bias “Associated” Charged Particle Density
About a factor of 2 increase in the “transverse” region! 1.96 TeV → 14 TeV (~factor of 7 increase) Tevatron LHC 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 TeV from PYTHIA Tune DW at the particle level (i.e. generator level). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Min-Bias “Associated” Charged Particle Density
35% more at RHIC means 26% less at the LHC! ~1.35 ~1.35 0.2 TeV → 14 TeV (~factor of 70 increase) RHIC 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 TeV from PYTHIA Tune DW and Tune DWT at the particle level (i.e. generator level). The STAR data from RHIC favors Tune DW! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Min-Bias “Associated” Charged Particle Density
~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 Tevatron LHC 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 TeV predicted by PYTHIA Tune DW at the particle level (i.e. generator level). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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” Preliminary ~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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Min-Bias “Associated” Charged Particle Density
Highest pT charged particle! “Associated” densities do not include PTmax! 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. Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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” events with 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!). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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” events with 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”). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Min-Bias “Associated” Charged Particle Density
“Toward” Region “Transverse” “Transverse” ~ factor of 2! 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 TeV with PTmax > 0.5, 1.0, 2.0, 5.0, and 10.0 GeV/c from PYTHIA Tune A (generator level). 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 from PYTHIA Tune A (generator level). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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“Associated” Charged Particle Density
PY Tune DW PY Tune DWPro PY Tune S320 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 GeV with PTmax > 2.0 GeV/c from PYTHIA Tune DW, Tune DWPro, and Tune S320 (generator level). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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 GeV with 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 GeV with PTmax > 2.0 GeV/c from PYTHIA Tune DW (generator level). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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 GeV with PTmax > 2.0 GeV/c from PYTHIA Tune DW (generator level). Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Min-Bias “Associated” Charged Particle Density
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 Tevatron LHC 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 TeV predicted by PYTHIA Tune DW at the particle level (i.e. generator level). Linear scale! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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Min-Bias “Associated” Charged Particle Density
LHC14 LHC10 LHC7 Tevatron 900 GeV RHIC 7 TeV → 14 TeV (UE increase ~20%) LHC7 LHC14 Linear on a log plot! 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 TeV predicted by PYTHIA Tune DW at the particle level (i.e. generator level). Log scale! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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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. CMS at the LHC UE studies at 900 GeV from CMS and ATLAS coming soon! LHC predictions! Lake Louise Winter Institute February 15, 2010 Rick Field – Florida/CDF/CMS
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