Toward an Understanding of Hadron-Hadron. Collisions From Feynman-Field to the LHC

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Toward an Understanding of Hadron-Hadron Collisions From Feynman-Field to the LHC Rick Field University of Florida Outline of Talk The old days of

Extrapolations from the Tevatron to RHIC and the LHC.

1 Toward an Understanding of Hadron-Hadron Collisions From Feynman-Field to the LHC Rick Field University of Florida Outline of Talk The old days of Feynman-Field Phenomenology. XXIèmes Rencontres de Blois Windows on the Universe June 2st - 26th, 2009 The present day QCD Monte-Carlo Model tunes. Extrapolations from the Tevatron to RHIC and the LHC. CDF Run 2 Proton Underlying Event Outgoing Parton PT(hard) Initial-State Radiation AntiProton Underlying Event The underlying event at STAR. Outgoing Parton Final-State Radiation LHC predictions! Summary & Conclusions. CMS at the LHC UE&MB@CMS Rick Field Florida/CDF/CMS Page

Toward and Understanding of Hadron-Hadron Collisions

2 Toward and Understanding of Hadron-Hadron Collisions Feynman-Field Phenomenology st hat! Feynman and Field From 7 GeV/c π 0 s to 600 GeV/c Jets. The early days of trying to understand and simulate hadronhadron collisions. Proton Underlying Event Outgoing Parton PT(hard) Initial-State Radiation AntiProton Underlying Event Outgoing Parton Final-State Radiation Rick Field Florida/CDF/CMS Page 2

3 Hadron-Hadron Collisions FF 977 What happens when two hadrons collide at high energy? 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. Hadron??? Hadron Parton-Parton Scattering Outgoing Parton Soft Collision (no large transverse momentum) Occasionally there will be a large transverse momentum meson. Question: Where did it come from? Hadron Hadron We assumed it came from quark-quark elastic scattering, but we did not know how to calculate it! Black-Box Model Outgoing Parton high P T meson Rick Field Florida/CDF/CMS Page 3

4 Hadron-Hadron Collisions FF 977 What happens when two hadrons collide at high energy? Hadron Feynman quote from FF??? The model we shall choose is not a popular one, Most of the time the hadrons ooze so that we will not duplicate too much of the through each other and work fall apart of others (i.e. who are similarly analyzing no hard scattering). The various outgoing models (e.g. constituent interchange particles continue in roughly model, multiperipheral the same models, etc.). We shall Parton-Parton Scattering direction as initial proton assume and that the high P Outgoing Parton T particles arise from antiproton. direct hard collisions between constituent quarks in the incoming particles, which Occasionally there will fragment be a large or cascade down Hadron into several hadrons. transverse momentum meson. Question: Where did it come from? Hadron Soft Collision (no large transverse momentum) Hadron We assumed it came from quark-quark elastic scattering, but we did not know how to calculate it! Black-Box Model Outgoing Parton high P T meson Rick Field Florida/CDF/CMS Page 4

5 Quark Distribution Functions determined from deep-inelastic lepton-hadron collisions Quark-Quark Black-Box Box Model FF 977 No gluons! Quark-Quark Cross-Section Unknown! Deteremined from hadron-hadron collisions. Quark Fragmentation Functions determined from e + e - annihilations Rick Field Florida/CDF/CMS Page 5

6 Quark Distribution Functions determined from deep-inelastic lepton-hadron collisions Quark-Quark Black-Box Box Model FF 977 Feynman quote from FF 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. No gluons! Quark-Quark Cross-Section Unknown! Deteremined from hadron-hadron collisions. Quark Fragmentation Functions determined from e + e - annihilations Rick Field Florida/CDF/CMS Page 6

7 Quark-Quark Black-Box Box Model Predict particle ratios FF 977 Predict increase with increasing CM energy W The underlying event (Beam-Beam Remnants)! Predict overall event topology (FFF paper 977) 7 GeV/c π 0 s! Rick Field Florida/CDF/CMS Page 7

8 Quark-Quark Black-Box Box Model Predict particle ratios FF 977 Predict increase with increasing CM energy W When Jim Cronin s group at the University of Chicago measured these rations and we knew we were on the right track! The underlying event (Beam-Beam Remnants)! Predict overall event topology (FFF paper 977) 7 GeV/c π 0 s! Rick Field Florida/CDF/CMS Page 8

9 QCD Approach: Quarks & Gluons Quark & Gluon Fragmentation Functions Q 2 dependence predicted from QCD FFF2 978 Parton Distribution Functions Q 2 dependence predicted from QCD Quark & Gluon Cross-Sections Calculated from QCD Rick Field Florida/CDF/CMS Page 9

10 QCD Approach: Quarks & Gluons Quark & Gluon Fragmentation Functions Q 2 dependence predicted from QCD FFF2 978 Parton Distribution Functions Q 2 dependence predicted from QCD 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. Quark & Gluon Cross-Sections Calculated from QCD Rick Field Florida/CDF/CMS Page 0

Feynman quote from FFF At the time of this writing, there is still no sharp

11 High P T Jets Feynman, Field, & Fox (978) CDF (2006) Predict large jet cross-section 30 GeV/c! 600 GeV/c Jets! 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 P T discussed here. Rick Field Florida/CDF/CMS Page

12 QCD Monte-Carlo Models: High Transverse Momentum Jets Hard Scattering Outgoing Parton Initial-State Radiation PT(hard) Hard Scattering Jet Jet Initial-State Radiation Outgoing Parton PT(hard) Hard Scattering Component Proton Underlying Event AntiProton Underlying Event Outgoing Parton Final-State Radiation Outgoing Parton Jet Final-State Radiation Proton Underlying Event AntiProton Underlying Event Underlying Event Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and finalstate 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). The underlying event is an unavoidable Of course the outgoing colored partons fragment into hadron jet and inevitably underlying event background to most collider observables observables receive contributions from initial and final-state radiation. and having good understand of it leads to more precise collider measurements! Rick Field Florida/CDF/CMS Page 2

13 QCD Monte-Carlo Models: Lepton-Pair Production High Lepton-Pair P T Z-Boson Production Anti-Lepton Outgoing Parton High PLepton-Pair T Z-Boson Production Jet Initial-State Radiation Outgoing Anti-Lepton Parton Final-State Radiation Hard Scattering Component Initial-State Radiation Final-State Radiation Proton Underlying Event AntiProton Underlying Event Z-boson Lepton Z-boson Lepton Proton Underlying Event AntiProton Underlying Event Underlying Event 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). The underlying event consists of the beam-beam remnants and from particles arising from soft or semi-soft multiple parton interactions (MPI). Of course the outgoing colored partons fragment into hadron jet and inevitably underlying event observables receive contributions from initial-state radiation. Rick Field Florida/CDF/CMS Page 3

14 CDF Run : Evolution of Charged Jets Underlying Event region very sensitive to the underlying event! Charged Jet # Direction Toward-Side Jet Charged Particle Correlations P T > 0.5 GeV/c η < CDF Run Analysis Charged Jet # Direction 2π Away Region Transverse Region Look at the charged particle density in the transverse region! φ Leading Jet Toward Region Transverse Region Away-Side Jet 0 Away Region - η + Look at charged particle correlations in the azimuthal angle relative to the leading charged particle jet. Define < 60 o as, 60 o < < 20 o as, and > 20 o as. All three regions have the same size in η-φ space, ηx = 2x20 o = 4π/3. Rick Field Florida/CDF/CMS Page 4

15 PYTHIA default parameters Parameter MSTP(8) MSTP(82) PARP(8) PARP(82) PARP(89) PARP(90) PARP(67) PYTHIA Defaults MPI constant probability , , , "Transverse" Charged Density scattering "Transverse" Charged Particle Density: dn/dηdφ CDF Data data uncorrected theory corrected Pythia (default) MSTP(82)= PARP(8) =.9 GeV/c PT(charged jet#) (GeV/c).8 TeV η <.0 PT>0.5 GeV CTEQ3L CTEQ4L CTEQ5L CDF Min-Bias CDF JET20 Plot shows the charged particle density versus P T (chgjet#) compared to the QCD hard scattering predictions of PYTHIA (P T (hard) > 0) using the default parameters for multiple parton interactions and CTEQ3L, CTEQ4L, and CTEQ5L. Note Change PARP(67) = 4.0 (< 6.38) PARP(67) =.0 (> 6.38) Default parameters give very poor description of the underlying event! Rick Field Florida/CDF/CMS Page 5

16 Parameter Default Tuning PYTHIA: Multiple Parton Interaction Parameters Description PARP(83) PARP(84) PARP(85) Double-Gaussian: Fraction of total hadronic matter within PARP(84) Double-Gaussian: Fraction of the overall hadron radius containing the fraction PARP(83) of the total hadronic matter. Determines the energy Probability that the MPI produces two gluons dependence of the MPI! with color connections to the nearest neighbors. Hard Core Color String Multiple Parton Interaction Color String PARP(86) 0.66 Probability that Affects the MPI the produces amount two of gluons either as described initial-state by PARP(85) radiation! or as a closed gluon loop. The remaining fraction consists of quark-antiquark pairs. Multiple Parton Determine Interaction by comparing with 630 GeV data! Color String PARP(89) PARP(82) PARP(90) TeV.9 GeV/c 0.6 Determines the reference energy E 0. The cut-off P T0 that regulates the 2-to-2 scattering divergence /PT 4 /(PT 2 +P T0 2 ) 2 Determines the energy dependence of the cut-off P T0 as follows P T0 (E cm ) = P T0 (E cm /E 0 ) ε with ε = PARP(90) PT0 (GeV/c) PYTHIA Hard-Scattering Cut-Off PT0 Take E 0 =.8 TeV ε = 0.25 (Set A)) PARP(67).0 A scale factor that determines the maximum parton virtuality for space-like showers. The larger the value of PARP(67) the more initialstate radiation. ε = 0.6 (default) 00,000 0,000 00,000 Reference point at.8 TeV CM Energy W (GeV) Rick Field Florida/CDF/CMS Page 6

17 PYTHIA CTEQ5L Parameter MSTP(8) MSTP(82) PARP(82) PARP(83) PARP(84) PARP(85) PARP(86) PARP(89) PARP(90) PARP(67) Tune B TeV New PYTHIA default (less initial-state radiation) 4.9 GeV.0 Run PYTHIA Tune A Tune A GeV TeV CDF Default! "Transverse" Charged Particle Density: dn/dηdφ "Transverse" Charged Density CDF Preliminary data uncorrected theory corrected CTEQ5L Plot shows the transverse charged particle density versus P T (chgjet#) compared to the QCD hard scattering predictions of two tuned versions of PYTHIA (CTEQ5L, Set B (PARP(67)=) and Set A (PARP(67)=4)). Old PYTHIA default (more initial-state radiation) PYTHIA (Set B) PARP(67)= PYTHIA (Set A) PARP(67)= PT(charged jet#) (GeV/c) Run Analysis.8 TeV η <.0 PT>0.5 GeV Rick Field Florida/CDF/CMS Page 7

18 Charged Density PTmax Direction ChgJet# Direction "Transverse" Charged Density "Transverse" Charged Particle Density: dn/dηdφ RDF Preliminary py Tune A generator level PTmax ChgJet# Jet#.96 TeV Charged Particles ( η <.0, PT>0.5 GeV/c) Jet# Direction PT(jet#) or PT(chgjet#) or PTmax (GeV/c) Shows the charged particle density in the transverse region for charged particles (p T > 0.5 GeV/c, η < ) at.96 TeV as defined by PTmax, PT(chgjet#), and PT(jet#) from PYTHIA Tune A at the particle level (i.e. generator level). Rick Field Florida/CDF/CMS Page 8

19 All use LO α s with Λ = 92 MeV! Parameter Tune AW Tune DW Tune D6 PYTHIA 6.2 Tunes PDF CTEQ5L CTEQ5L CTEQ6L UE Parameters MSTP(8) MSTP(82) PARP(82) GeV 4.9 GeV 4.8 GeV Uses CTEQ6L PARP(83) PARP(84) PARP(85) Tune A energy dependence! ISR Parameter PARP(86) PARP(89) TeV.0.8 TeV.0.8 TeV PARP(90) PARP(62) PARP(64) PARP(67) MSTP(9) PARP(9) PARP(93) Intrinsic KT Rick Field Florida/CDF/CMS Page 9

20 All use LO α s with Λ = 92 MeV! Parameter PYTHIA 6.2 Tunes Tune DWT Tune D6T ATLAS PDF CTEQ5L CTEQ6L CTEQ5L MSTP(8) UE Parameters MSTP(82) PARP(82).9409 GeV.8387 GeV.8 GeV PARP(83) PARP(84) ATLAS energy dependence! PARP(85) ISR Parameter PARP(86) PARP(89).0.96 TeV.0.96 TeV TeV PARP(90) PARP(62) PARP(64) PARP(67) MSTP(9) PARP(9) PARP(93) Intrinsic KT Rick Field Florida/CDF/CMS Page 20

21 PYTHIA 6.2 Tunes All use LO α s with Λ = 92 MeV! Tune A UE Parameters ISR Parameter Tune D Intrinsic KT Parameter Tune DWT Tune D6T ATLAS PDF CTEQ5L CTEQ6L CTEQ5L MSTP(8) MSTP(82) PARP(82).9409 GeV.8387 GeV.8 GeV PARP(83) PARP(84) 0.5 Tune AW Tune B Tune BW PARP(85) PARP(86).0.0 PARP(89).96 TeV.96 TeV PARP(90) PARP(62) PARP(64) PARP(67) MSTP(9) PARP(9) Tune 2. DW 2. PARP(93) TeV Tune D6 5.0 ATLAS energy dependence! Tune D6T Rick Field Florida/CDF/CMS Page 2

22 PYTHIA 6.2 Tunes All use LO α s with Λ = 92 MeV! Tune A UE Parameters ISR Parameter Tune D Intrinsic KT Parameter Tune DWT Tune D6T ATLAS PDF CTEQ5L CTEQ6L CTEQ5L MSTP(8) MSTP(82) PARP(82).9409 GeV.8387 GeV.8 GeV PARP(83) PARP(84) 0.5 Tune AW Tune B PARP(85) These are Tune BW.0 old PYTHIA tunes! There are new tunes by PARP(86) PARP(89) Peter Skands.96 TeV (Tune.96 S320, TeV update.0 TeV of S0) PARP(90) Peter Skands (Tune N324, N0CR) PARP(62) Hendrik Hoeth (Tune P329, Professor ) PARP(64) PARP(67) MSTP(9) PARP(9) Tune 2. DW 2. PARP(93) Tune D6 5.0 ATLAS energy dependence! Tune D6T Rick Field Florida/CDF/CMS Page 22

23 "Transverse" Charged Density Min-Bias Associated Charged Particle Density 35% more at RHIC means "Transverse" Charged Particle Density: dn/dηdφ 26% less at the LHC! "Transverse" Charged Particle Density: dn/dηdφ RDF Preliminary generator level Min-Bias 0.2 TeV ~.35 PY Tune DW PY Tune DWT Charged Particles ( η <.0, PT>0.5 GeV/c) PTmax (GeV/c) "Transverse" Charged Density RDF Preliminary generator level Min-Bias 4 TeV PY Tune DWT ~.35 Charged Particles ( η <.0, PT>0.5 GeV/c) PTmax (GeV/c) PY Tune DW RHIC PTmax Direction 0.2 TeV 4 TeV (~factor of 70 increase) LHC PTmax Direction Shows the associated charged particle density in the transverse regions as a function of PTmax for charged particles (p T > 0.5 GeV/c, η <, not including PTmax) for min-bias events at 0.2 TeV and 4 TeV from PYTHIA Tune DW and Tune DWT at the particle level (i.e. generator level). The STAR data from RHIC favors Tune DW! Rick Field Florida/CDF/CMS Page 23

24 Min-Bias Associated Charged Particle Density "Transverse" Charged Density "Transverse" Charged Particle Density: dn/dηdφ RDF Preliminary py Tune DW generator level ~.9 ~2.7 Min-Bias Charged Particles ( η <.0, PT>0.5 GeV/c) PTmax (GeV/c) 0.2 TeV 4 TeV.96 TeV RHIC PTmax Direction 0.2 TeV.96 TeV (UE increase ~2.7 times) Tevatron PTmax Direction.96 TeV 4 TeV (UE increase ~.9 times) LHC PTmax Direction Shows the associated charged particle density in the transverse region as a function of PTmax for charged particles (p T > 0.5 GeV/c, η <, not including PTmax) for min-bias events at 0.2 TeV,.96 TeV and 4 TeV predicted by PYTHIA Tune DW at the particle level (i.e. generator level). Rick Field Florida/CDF/CMS Page 24

25 The Underlying Event at STAR At STAR they have measured the underlying event at W = 200 GeV ( η <, p T > 0.2 GeV) and compared their uncorrected data with PYTHIA Tune A + STAR-SIM. Rick Field Florida/CDF/CMS Page 25

26 The Underlying Event at STAR At STAR they have measured the underlying event at W = 200 GeV ( η <, p T > 0.2 GeV) and compared their uncorrected data with PYTHIA Tune A + STAR-SIM. Rick Field Florida/CDF/CMS Page 26

27 "Transverse" Charged Density RDF LHC Prediction! "Transverse" Charged Particle Density: dn/dηdφ RDF Preliminary generator level Min-Bias.96 TeV PY64 Tune S320 PY64 Tune P329 PY64 Tune N PTmax (GeV/c) Min-Bias Associated Charged Particle Density PY Tune A Charged Particles ( η <.0, PT>0.5 GeV/c) "Transverse" Charged Density "Transverse" Charged Particle Density: dn/dηdφ RDF Preliminary generator level PY ATLAS PY Tune A PY64 Tune S320 PY Tune DW Min-Bias 4 TeV Charged Particles ( η <.0, PT>0.5 GeV/c) PTmax (GeV/c) PY64 Tune P329 PY Tune DWT PTmax Direction PTmax Direction Tevatron LHC Shows the associated charged particle density in the transverse region as a function of PTmax for charged particles (p T > 0.5 GeV/c, η <, not including PTmax) for min-bias events at.96 TeV from PYTHIA Tune A, Tune S320, Tune N324, and Tune P329 at the particle level (i.e. generator level). Extrapolations of PYTHIA Tune A, Tune DW, Tune DWT, Tune S320, Tune P329, and pyatlas to the LHC. Rick Field Florida/CDF/CMS Page 27

28 "Transverse" Charged Density RDF LHC Prediction! "Transverse" Charged Particle Density: dn/dηdφ RDF Preliminary generator level Min-Bias Associated Charged Particle Density "Transverse" Charged Density "Transverse" Charged Particle Density: dn/dηdφ PY Tune A 0.8 PY64 Tune P329 PY64 Tune N324 PY Tune A PY64 Tune S320 PY64 Tune S320 PY Tune DW Min-Bias Min-Bias Charged Particles ( η <.0, PT>0.5 GeV/c).96 TeV 4 TeV Charged Particles ( η <.0, PT>0.5 GeV/c) If the LHC data 0.0 are not in PTmax Direction PY64 Tune P329 PTmax (GeV/c).6.2 RDF Preliminary generator level the range shown here then we learn new (QCD) physics! PY ATLAS PTmax (GeV/c) PTmax Direction PY Tune DWT Tevatron LHC Shows the associated charged particle density in the transverse region as a function of PTmax for charged particles (p T > 0.5 GeV/c, η <, not including PTmax) for min-bias events at.96 TeV from PYTHIA Tune A, Tune S320, Tune N324, and Tune P329 at the particle level (i.e. generator level). Extrapolations of PYTHIA Tune A, Tune DW, Tune DWT, Tune S320, Tune P329, and pyatlas to the LHC. Rick Field Florida/CDF/CMS Page 28

29 Z-Boson: Towards Region "Toward" Charged Particle Density: RDF LHC dn/dηdφ Prediction! "Toward" Charged Particle Density: dn/dηdφ "Toward" Charged Density RDF Preliminary generator level PY64 Tune S320 PY Tune DW PY64 Tune P329 PY Tune AW Drell-Yan.96 TeV 70 < M(pair) < 0 GeV Charged Particles ( η <.0, PT>0.5 GeV/c) "Toward" Charged Density RDF Preliminary generator level Drell-Yan 4 TeV PY64 Tune P329 PY Tune DWT PY64 Tune S320 PY Tune DW 70 < M(pair) < 0 GeV PY ATLAS Charged Particles ( η <.0, PT>0.5 GeV/c) Lepton-Pair PT (GeV/c) Lepton-Pair PT (GeV/c) Z-BosonDirection Z-BosonDirection Tevatron LHC Data at.96 TeV on the density of charged particles, dn/dηdφ, with p T > 0.5 GeV/c and η < for Z- Boson events as a function of P T (Z) for the toward region from PYTHIA Tune AW, Tune DW, Tune S320, and Tune P329 at the particle level (i.e. generator level). Extrapolations of PYTHIA Tune AW, Tune DW, Tune DWT, Tune S320, and Tune P329 to the LHC. Rick Field Florida/CDF/CMS Page 29

30 Z-Boson: Towards Region "Toward" Charged Density "Toward" Charged Particle Density: RDF LHC dn/dηdφ Prediction! RDF Preliminary generator level PY64 Tune S320 PY Tune DW Z-BosonDirection PY64 Tune P Lepton-Pair PT (GeV/c) PY Tune AW Drell-Yan.96 TeV 70 < M(pair) < 0 GeV Charged Particles ( η <.0, PT>0.5 GeV/c) "Toward" Charged Density "Toward" Charged Particle Density: dn/dηdφ RDF Preliminary generator level Drell-Yan 4 TeV PY64 Tune P329 If the LHC data are not in 0.0 the range shown here then we learn new (QCD) physics! PY Tune DWT PY64 Tune S Lepton-Pair PT (GeV/c) Z-BosonDirection PY Tune DW 70 < M(pair) < 0 GeV PY ATLAS Charged Particles ( η <.0, PT>0.5 GeV/c) Tevatron LHC Data at.96 TeV on the density of charged particles, dn/dηdφ, with p T > 0.5 GeV/c and η < for Z- Boson events as a function of P T (Z) for the toward region from PYTHIA Tune AW, Tune DW, Tune S320, and Tune P329 at the particle level (i.e. generator level). Extrapolations of PYTHIA Tune AW, Tune DW, Tune DWT, Tune S320, and Tune P329 to the LHC. Rick Field Florida/CDF/CMS Page 30

31 Charged Particle Density RDF Preliminary generator level Charged Particle Density: dn/d /dη Charged Particle Density: dn/dη PY64 Tune P329 Charged Particles (all PT) PY Tune DW PY64 Tune S PseudoRapidity η Min-Bias.96 TeV RDF LHC Prediction! PY Tune A Charged Particle Density RDF Preliminary generator level PY ATLAS Charged Particle Density: dn/dη PY64 Tune S320 Charged Particles (all PT) PY Tune DW PseudoRapidity η PY Tune A Min-Bias 4 TeV PY64 Tune P329 PY Tune DWT Minumum Bias Collisions Minumum Bias Collisions Proton AntiProton Tevatron LHC Proton Proton Charged particle (all p T ) pseudo-rapidity distribution, dnchg/dηdφ, at.96 TeV for inelastic non-diffractive collisions from PYTHIA Tune A, Tune DW, Tune S320, and Tune P324. Extrapolations (all pt) of PYTHIA Tune A, Tune DW, Tune S320, Tune P324. and ATLAS to the LHC. Rick Field Florida/CDF/CMS Page 3

32 Charged Particle Density RDF Preliminary generator level Charged Particle Density: dn/d /dη Charged Particle Density: dn/dη Charged Particle Density Charged Particle Density: dn/dη PY ATLAS 3.0 PY Tune DW 4.0 PY Tune DW 2.0 PY64 Tune S320 PY Tune A PY64 Tune S320 PY64 Tune P Min-Bias Min-Bias Charged Particles (all PT).96 TeV Charged Particles (all PT) 4 TeV 0.0 If the LHC data 0.0 are not in Minumum Bias Collisions PseudoRapidity η RDF LHC Prediction! PY Tune A RDF Preliminary generator level the range shown here then we learn new (QCD) physics! PseudoRapidity η Minumum Bias Collisions PY64 Tune P329 PY Tune DWT Proton AntiProton Tevatron LHC Proton Proton Charged particle (all p T ) pseudo-rapidity distribution, dnchg/dηdφ, at.96 TeV for inelastic non-diffractive collisions from PYTHIA Tune A, Tune DW, Tune S320, and Tune P324. Extrapolations (all pt) of PYTHIA Tune A, Tune DW, Tune S320, Tune P324. and ATLAS to the LHC. Rick Field Florida/CDF/CMS Page 32

33 Summary & Conclusions We are making good progress in understanding and modeling the underlying event. RHIC data at 200 GeV are very important! The new Pythia p T ordered tunes (py64 S320 and py64 P329) are very similar to Tune A, Tune AW, and Tune DW. At present the new tunes do not fit the data better than Tune AW and Tune DW. However, the new tune are theoretically preferred! It is clear now that the default value PARP(90) = 0.6 is not correct and the value should be closer to the Tune A value of The new and old PYTHIA tunes are beginning to converge and I believe we are finally in a position to make some legitimate predictions at the LHC! All tunes with the default value PARP(90) = 0.6 are wrong and are overestimating the activity of min-bias and the underlying event at the LHC! This includes all my T tunes and the ATLAS tunes! Need to measure Min-Bias and the underlying event at the LHC as soon as possible to see if there is new QCD physics to be learned! PT0 (GeV/c) Proton Underlying Event Outgoing Parton PYTHIA Final-State Radiation UE&MB@CMS Outgoing Parton PT(hard) Hard-Scattering Cut-Off PT0 ε = 0.25 (Set A)) ε = 0.6 (default) Initial-State Radiation AntiProton Underlying Event 00,000 0,000 00,000 CM Energy W (GeV) Rick Field Florida/CDF/CMS Page 33

34 Summary & Conclusions We are making good progress in understanding and modeling the underlying event. RHIC data at 200 GeV are very important! The new Pythia p T ordered tunes (py64 S320 and py64 P329) are very similar to Tune A, Tune AW, and Tune DW. At present the new tunes do not fit the data better than Tune AW and Tune DW. However, the new tune are theoretically preferred! It is clear now that the default value PARP(90) = 0.6 is not correct and the value should be closer to the Tune A value of The new and old PYTHIA tunes are beginning to converge and I believe we are finally in a position to make some legitimate predictions at the LHC! All tunes with the default value PARP(90) = 0.6 are wrong and are overestimating the activity of min-bias and the underlying event at the LHC! This includes all my T tunes and the ATLAS tunes! Need to measure Min-Bias and the underlying event at the LHC as soon as possible to see if there is new QCD physics to be learned! PT0 (GeV/c) Proton Underlying Event Outgoing Parton PYTHIA Outgoing Parton of Tune A at the Tevatron! PT(hard) Final-State Radiation Hard-Scattering Cut-Off PT0 UE&MB@CMS However, I believe that the better fits to the LEP fragmentation data at high z will lead to small improvements ε = 0.25 (Set A)) ε = 0.6 (default) Initial-State Radiation AntiProton Underlying Event 00,000 0,000 00,000 CM Energy W (GeV) Rick Field Florida/CDF/CMS Page 34

The LHC Physics Environment

The LHC Physics Environment Talk : What We Have Learned at the Tevatron Rick Field University of Florida Outline of Talk The old days of Feynman-Field Phenomenology. Review what we learned about minbias,