International Symposium on Multiparticle Dynamics 22 Years! Many of you were at Volendam! Rick Field (experimenter?) “Min Bias and the Underlying Events in Run 2 at CDF” Rick Field (theorist?) “Jet Formation in QCD” ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 1 “Min-Bias” and the “Underlying Event” in Run 2 at CDF Outline of Talk Scattering Multiple“Hard” Parton Interactions Discuss briefly the components of the “underlying event” of a hard scattering as described by the QCD parton-shower Monte-Carlo Models. OutgoingParton Parton Outgoing PT(hard) PT(hard) Proton Proton AntiProton AntiProton Underlying Event Underlying Event Underlying Event Underlying Event Initial-State Radiation Final-State Radiation Outgoing Parton Outgoing Parton Review the CDF Run 1 analysis which was used to Charged Particle Jet tune the multiple parton interaction parameters in PYTHIA (i.e. Tune A and Tune B). Calorimeter Jet Study the “underlying event” in CDF Run 2 as defined by the leading calorimeter jet and compare with PYTHIA Tune A (with MPI) and HERWIG (without MPI). JetClu R = 0.7 ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 2 The “Underlying Event” in Hard Scattering Processes What happens when a high energy proton and an antiproton collide? “Min-Bias” “Soft” Collision (no hard scattering) ProtonProton AntiProton AntiProton 2 TeV Most of the time the proton and antiproton ooze through each other and fall apart (i.e. no hard scattering). “Hard” Scattering Outgoing Parton The outgoing particles continue in PT(hard) roughly the same direction as initial Are proton and antiproton. A “Min-Bias” Proton these AntiProton collision. the Underlying Event Underlying Event Initial-State Occasionally there will be a “hard” same? Radiation parton-parton collision resulting in large Final-State Radiation No! transverse momentum outgoing partons. Outgoing Parton Also a “Min-Bias” collision. The “underlying event” is everything except the two outgoing hard scattered “jets”. It is an unavoidable background to many collider observables. ISMD2004 July 27, 2004 “Underlying Event” Proton AntiProton Beam-Beam Remnants Rick Field - Florida/CDF Beam-Beam Remnants “underlying event” has initial-state radiation! Initial-State Radiation Page 3 Beam-Beam Remnants “Hard” Collision outgoing parton “Hard” Component Maybe not all “soft”! “Soft?” Component AntiProton Proton initial-state radiation initial-state radiation + Beam-Beam Remnants outgoing parton outgoing jet final-state radiation final-state radiation The underlying event in a hard scattering process has a “hard” component (particles that arise from initial & final-state radiation and from the outgoing hard scattered partons) and a “soft?” component (“beam-beam remnants”). Clearly? the “underlying event” in a hard scattering process should not look like a “MinBias” event because of the “hard” component (i.e. initial & final-state radiation). However, perhaps “Min-Bias” collisions are a good model for the “beam-beam remnant” component of the “underlying event”. “Min-Bias” Collision “Soft?” Component color string Are these the same? Hadron Hadron color string Beam-Beam Remnants The “beam-beam remnant” component is, however, color connected to the “hard” component so this comparison is (at best) an approximation. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 4 MPI: Multiple Parton Interactions “Hard” Collision Multiple Parton Interaction outgoing parton “Hard” Component “Semi-Hard” MPI “Soft” Component AntiProton Proton initial-state radiation outgoing parton final-state radiation or + initial-state radiation outgoing jet final-state radiation 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”. Beam-Beam Remnants color string color string 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). ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 5 The “Transverse” Regions as defined by the Leading Jet Jet #1 Direction “Transverse” region is very sensitive to the “underlying event”! Charged Particle Correlations 2p pT > 0.5 GeV/c |h| < 1 Away Region “Toward-Side” Jet Look at the charged particle density in the “transverse” region! Jet #1 Direction Transverse Region 1 “Toward” “Toward” “Transverse” “Transverse” “Away” “Trans 1” Leading Jet “Trans 2” Toward Region Transverse Region 2 “Away” “Away-Side” Jet Away Region 0 -1 h +1 Look at charged particle correlations in the azimuthal angle relative to the leading calorimeter jet (JetClu R = 0.7, |h| < 2). o o o o o Define || < 60 as “Toward”, 60 < - < 120 and 60 < < 120 as “Transverse 1” and o “Transverse 2”, and || > 120 as “Away”. Each of the two “transverse” regions have o area h = 2x60 = 4p/6. The overall “transverse” region is the sum of the two o transverse regions (h = 2x120 = 4p/3). ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 6 Particle Densities h = 4p = 12.6 2p 31 charged charged particles particle Charged Particles pT > 0.5 GeV/c |h| < 1 CDF Run 2 “Min-Bias” CDF Run 2 “Min-Bias” Observable Average Nchg Number of Charged Particles (pT > 0.5 GeV/c, |h| < 1) 3.17 +/- 0.31 0.252 +/- 0.025 PTsum (GeV/c) Scalar pT sum of Charged Particles (pT > 0.5 GeV/c, |h| < 1) 2.97 +/- 0.23 0.236 +/- 0.018 Average Density per unit h- chg/dhd = 1/4p 3/4p = 0.08 0.24 dNchg 13 GeV/c PTsum 0 -1 h +1 Divide by 4p dPTsum/dhd = 1/4p 3/4p GeV/c = 0.08 0.24 GeV/c Study the charged particles (pT > 0.5 GeV/c, |h| < 1) and form the charged particle density, dNchg/dhd, and the charged scalar pT sum density, dPTsum/dhd. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 7 PYTHIA 6.206 Defaults MPI constant probability scattering PYTHIA default parameters 6.115 6.125 6.158 6.206 MSTP(81) 1 1 1 1 MSTP(82) 1 1 1 1 PARP(81) 1.4 1.9 1.9 1.9 PARP(82) 1.55 2.1 2.1 1.9 PARP(89) 1,000 1,000 1,000 PARP(90) 0.16 0.16 0.16 4.0 1.0 1.0 PARP(67) 4.0 1.00 "Transverse" Charged Density Parameter "Transverse" Charged Particle Density: dN/dhd CDF Data Pythia 6.206 (default) MSTP(82)=1 PARP(81) = 1.9 GeV/c data uncorrected theory corrected 0.75 Run 1 Analysis 0.50 0.25 1.8 TeV |h|<1.0 PT>0.5 GeV 0.00 0 5 10 15 20 25 30 35 40 45 50 PT(charged jet#1) (GeV/c) CTEQ3L CTEQ4L CTEQ5L CDF Min-Bias CDF JET20 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. Note Change PARP(67) = 4.0 (< 6.138) PARP(67) = 1.0 (> 6.138) ISMD2004 July 27, 2004 Default parameters give very poor description of the “underlying event”! Rick Field - Florida/CDF Page 10 Tuned PYTHIA 6.206 Double Gaussian PYTHIA 6.206 CTEQ5L Tune B Tune A MSTP(81) 1 1 MSTP(82) 4 4 PARP(82) 1.9 GeV 2.0 GeV PARP(83) 0.5 0.5 PARP(84) 0.4 0.4 PARP(85) 1.0 0.9 PARP(86) 1.0 0.95 PARP(89) 1.8 TeV 1.8 TeV PARP(90) 0.25 0.25 PARP(67) 1.0 4.0 New PYTHIA default (less initial-state radiation) ISMD2004 July 27, 2004 1.00 "Transverse" Charged Density Parameter "Transverse" Charged Particle Density: dN/dhd CDF Preliminary PYTHIA 6.206 (Set A) PARP(67)=4 data uncorrected theory corrected 0.75 Run 1 Analysis 0.50 0.25 CTEQ5L PYTHIA 6.206 (Set B) PARP(67)=1 1.8 TeV |h|<1.0 PT>0.5 GeV 0.00 0 5 10 15 20 25 30 35 40 45 50 PT(charged jet#1) (GeV/c) 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) and Set A (PARP(67)=4)). Old PYTHIA default (more initial-state radiation) Rick Field - Florida/CDF Page 11 Tuned PYTHIA 6.206 “Transverse” PT Distribution "Transverse" Charged Particle Density "Transverse" Charged Particle Density: dN/dhd 1.0E+00 CDF Preliminary PYTHIA 6.206 (Set A) PARP(67)=4 data uncorrected theory corrected 0.75 CDF Data 0.50 0.25 CTEQ5L PYTHIA 6.206 (Set B) PARP(67)=1 0.00 0 5 10 15 20 25 Charged Density dN/dhddPT (1/GeV/c) "Transverse" Charged Density 1.00 PT(chgjet#1) > 30 GeV/c 1.0E-01 data uncorrected theory corrected PYTHIA 6.206 Set A PARP(67)=4 1.0E-02 Hear more about PARP(67) in Lee Sawyer’s talk on Wednesday! 1.8 TeV |h|<1.0 PT>0.5 GeV 30 35 40 45 PT(charged jet#1) (GeV/c) PT(charged jet#1) > 30 GeV/c 50 1.0E-03 1.0E-04 PT(chgjet#1) > 5 GeV/c 1.0E-05 PYTHIA 6.206 Set B PARP(67)=1 1.8 TeV |h|<1 PT>0.5 GeV/c PARP(67)=4.0 (old default) is favored over PARP(67)=1.0 (new default)! 1.0E-06 0 Can we distinguish between 2 4 6 8 10 12 PARP(67)=1 and PARP(67)=4? PT(charged) (GeV/c) No way! Right! 14 Compares the average “transverse” charge particle density (|h|<1, PT>0.5 GeV) versus PT(charged jet#1) and the PT distribution of the “transverse” density, dNchg/dhddPT with the QCD Monte-Carlo predictions of two tuned versions of PYTHIA 6.206 (PT(hard) > 0, CTEQ5L, Set B (PARP(67)=1) and Set A (PARP(67)=4)). ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 12 PYTHIA 6.206 Tune A (CDF Default) Describes the rise from “Min-Bias” to 1.0E+00 “underlying event”! "Transverse" Charged Particle Density: dN/dhd 1.00 PYTHIA 6.206 Set A data uncorrected theory corrected 0.75 0.50 0.25 1.8 TeV |h|<1.0 PT>0.5 GeV/c 0.00 0 5 10 15 20 25 30 35 40 45 PT(charged jet#1) (GeV/c) Charged Particle Density: dN/dhd 1.0 CDF Published dN/dhd “Min-Bias” 50 Set A PT(charged jet#1) > 30 GeV/c “Transverse” <dNchg/dhd> = 0.60 0.8 0.6 PYTHIA 6.206 Set A CDF Run 1 Charged Density dN/dhddPT (1/GeV/c) "Transverse" Charged Density CDF Run 1 Charged Particle Density data uncorrected theory corrected "Transverse" PT(chgjet#1) > 5 GeV/c 1.0E-01 "Transverse" PT(chgjet#1) > 30 GeV/c 1.0E-02 1.0E-03 1.0E-04 CDF Min-Bias CTEQ5L 1.8 TeV |h|<1 PT>0.5 GeV/c 0.4 1.0E-05 Set A Min-Bias <dNchg/dhd> = 0.24 0 0.2 2 4 6 8 10 12 14 Pythia 6.206 Set A 1.8 TeV all PT CDF Min-Bias 1.8 TeV PT(charged) (GeV/c) 0.0 -4 -3 -2 -1 0 1 2 3 4 Pseudo-Rapidity h Compares the average “transverse” charge particle density (|h|<1, PT>0.5 GeV) versus PT(charged jet#1) and the PT distribution of the “transverse” and “Min-Bias” densities with the QCD Monte-Carlo predictions of a tuned version of PYTHIA 6.206 (PT(hard) > 0, CTEQ5L, Set A). Describes “Min-Bias” collisions! Describes the “underlying event”! ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 13 Charged Particle Density Dependence Run 2 Charged Particle Density: dN/dhd Log Scale! Jet #1 Direction 10.0 30 < ET(jet#1) < 70 GeV “Toward” “Transverse” “Transverse” Jet #3 “Away” Charged Particle Density CDF Preliminary “Toward-Side” Jet data uncorrected "Transverse" Region 1.0 Jet#1 Charged Particles (|h|<1.0, PT>0.5 GeV/c) “Away-Side” “Away-Side” Jet Jet 0.1 0 30 60 90 Min-Bias 0.25 per unit h- 120 150 180 210 (degrees) 240 270 300 Leading Jet 330 360 Shows the dependence of the charged particle density, dNchg/dhd, for charged particles in the range pT > 0.5 GeV/c and |h| < 1 relative to jet#1 (rotated to 270o) for “leading jet” events 30 < ET(jet#1) < 70 GeV. Also shows charged particle density, dNchg/dhd, for charged particles in the range pT > 0.5 GeV/c and |h| < 1 for “min-bias” collisions. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 14 Refer to this as a “Leading Jet” event Charged Particle Density Dependence Run 2 Jet #1 Direction Particle Density: Density: dN/dhd dN/dhd Charged Particle “Toward” “Transverse” CDF Preliminary “Transverse” “Away” Refer to this as a “Back-to-Back” event Jet #1 Direction “Toward” “Transverse” Density Charged Particle Density Subset 10.0 10.0 data uncorrected 30 << ET(jet#1) ET(jet#1)<<70 70GeV GeV 30 Back-to-Back Leading Jet Min-Bias "Transverse" "Transverse" Region Region 1.0 1.0 Jet#1 Jet#1 Charged Particles Charged (|h|<1.0, PT>0.5 GeV/c) (|h|<1.0, “Transverse” 0.1 0.1 “Away” 00 30 60 90 120 150 180 180 210 210 240 240 270 270 300 300 330 330 360 360 (degrees) (degrees) Jet #2 Direction Look at the “transverse” region as defined by the leading jet (JetClu R = 0.7, |h| < 2) or by the leading two jets (JetClu R = 0.7, |h| < 2). “Back-to-Back” events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back-to-back” (12 > 150o) with almost equal transverse energies (ET(jet#2)/ET(jet#1) > 0.8). Shows the dependence of the charged particle density, dNchg/dhd, for charged particles in the range pT > 0.5 GeV/c and |h| < 1 relative to jet#1 (rotated to 270o) for 30 < ET(jet#1) < 70 GeV for “Leading Jet” and “Back-to-Back” events. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 15 “Transverse” PTsum Density versus ET(jet#1) Run 2 Jet #1 Direction “Toward” “Transverse” “Transverse” “Away” “Back-to-Back” Jet #1 Direction “Toward” “Transverse” "AVE Transverse" PTsum Density: dPT/dhd 1.4 “Transverse” "Transverse" PTsum Density (GeV/c) “Leading Jet” uncorrected datadata uncorrected theory + CDFSIM PY Tune A 1.0 0.8 0.6 0.4 Back-to-Back HW 0.2 1.96 TeV Charged Particles (|h|<1.0, PT>0.5 GeV/c) 0.0 0 50 “Away” Jet #2 Direction Leading Jet 2 Preliminary CDF Run Preliminary 1.2 100 150 200 250 ET(jet#1) (GeV) Min-Bias 0.24 GeV/c per unit h- Shows the average charged PTsum density, dPTsum/dhd, in the “transverse” region (pT > 0.5 GeV/c, |h| < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events. Compares the (uncorrected) data with PYTHIA Tune A and HERWIG after CDFSIM. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 16 “TransMIN” PTsum Density versus ET(jet#1) “Leading Jet” Jet #1 Direction "MIN Transverse" PTsum Density: dPT/dhd “Toward” “TransMAX” "Transverse" PTsum Density (GeV/c) 0.6 CDF Run 2 Preliminary Jet #1 Direction “TransMIN” “Away” 1.96 TeV data uncorrected theory + CDFSIM Leading Jet Jet Leading PY Tune A 0.4 “Toward” “Back-to-Back” Jet #1 Direction “Toward” “TransMAX” “TransMIN” “Away” Jet #2 Direction “TransMAX” 0.2 “TransMIN” Min-Bias “Away” Back-to-Back Back-to-Back HW Charged Particles (|h|<1.0, PT>0.5 GeV/c) 0.0 0 50 “transMIN” is very sensitive to the “beam-beam remnant” component of the “underlying event”! 100 150 200 250 ET(jet#1) (GeV) Use the leading jet to define the MAX and MIN “transverse” regions on an event-byevent basis with MAX (MIN) having the largest (smallest) charged particle density. Shows the “transMIN” charge particle density, dNchg/dhd, for pT > 0.5 GeV/c, |h| < 1 versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 17 “Transverse” PTsum Density PYTHIA Tune A vs HERWIG “Leading Jet” Jet #1 Direction "AVE Transverse" PTsum Density: dPT/dhd “Toward” “Transverse” “Transverse” “Away” “Back-to-Back” Jet #1 Direction “Toward” “Transverse” “Transverse” "Transverse" PTsum Density (GeV/c) 1.4 Leading Jet CDF Preliminary 1.2 data uncorrected theory + CDFSIM PY Tune A 1.0 0.8 0.6 0.4 Back-to-Back HW 0.2 1.96 TeV Charged Particles (|h|<1.0, PT>0.5 GeV/c) 0.0 0 50 100 150 200 250 ET(jet#1) (GeV) “Away” Jet #2 Direction Now look in detail at “back-to-back” events in the region 30 < ET(jet#1) < 70 GeV! Shows the average charged PTsum density, dPTsum/dhd, in the “transverse” region (pT > 0.5 GeV/c, |h| < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events. Compares the (uncorrected) data with PYTHIA Tune A and HERWIG after CDFSIM. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 18 Charged PTsum Density PYTHIA Tune A vs HERWIG HERWIG (without multiple parton interactions) does not produces enough PTsum in the “transverse” region for 30 < ET(jet#1) < 70 GeV! Charged PTsum Density: dPT/dhd Charged PTsum Density: dPT/dhd 100.0 Charged Particles 30 < ET(jet#1) < 70 GeV (|h|<1.0, PT>0.5 GeV/c) Back-to-Back PY Tune A Charged PTsum Density (GeV/c) Charged PTsum Density (GeV/c) 100.0 10.0 1.0 HERWIG 10.0 "Transverse" Region 1.0 Hear more about the CDF Preliminary distribution of charged particles within jets in Sasha Pronko’s talk on Thursday! Data - Theory: Charged PTsum Density dPT/dhd Data - Theory: Charged PTsum Density dPT/dhd CDF Preliminary Jet#1 "Transverse" Region data uncorrected theory + CDFSIM 0.1 Charged Particles 30 < ET(jet#1) < 70 GeV (|h|<1.0, PT>0.5 GeV/c) Back-to-Back Jet#1 data uncorrected theory + CDFSIM 0.1 0 30 60 90 120 150 180 210 240 270 300 330 360 0 30 60 90 120 (degrees) 180 210 240 270 300 330 360 300 330 360 (degrees) 2 2 data uncorrected theory + CDFSIM 1 Back-to-Back 30 < ET(jet#1) < 70 GeV PYTHIA Tune A CDF Preliminary Data - Theory (GeV/c) CDF Preliminary Data - Theory (GeV/c) 150 0 -1 "Transverse" Region Charged Particles (|h|<1.0, PT>0.5 GeV/c) data uncorrected theory + CDFSIM 1 30 < ET(jet#1) < 70 GeV Back-to-Back HERWIG 0 -1 "Transverse" Region Charged Particles (|h|<1.0, PT>0.5 GeV/c) Jet#1 Jet#1 -2 -2 0 30 60 90 120 150 180 210 240 270 300 330 360 0 30 90 120 150 180 210 240 270 (degrees) (degrees) ISMD2004 July 27, 2004 60 Rick Field - Florida/CDF Page 19 “Transverse” PTmax versus ET(jet#1) Jet #1 Direction “Leading Jet” “TransMIN” Highest“TransMAX” pT particle in the “transverse” region! “Back-to-Back” “Away” Jet #1 Direction “Toward” “TransMAX” PTmaxT PTmaxT “TransMIN” “Away” "Transverse" PTmax (GeV/c) Jet #1 Direction “Toward” PTmaxT "Transverse" Charged PTmax 3.0 CDF Run 2 Preliminary 1.96 TeV 2.5 data uncorrected Leading Jet 2.0 “Toward” 1.5 “TransMAX” 1.0 “TransMIN” 0.5“Away” Min-Bias Back-to-Back Charged Particles (|h|<1.0, PT>0.5 GeV/c) 0.0 0 50 100 150 200 250 ET(jet#1) (GeV) Jet #2 Direction Min-Bias Use the leading jet to define the “transverse” region and look at the maximum pT charged particle in the “transverse” region, PTmaxT. Shows the average PTmaxT, in the “transverse” region (pT > 0.5 GeV/c, |h| < 1) versus ET(jet#1) for “Leading Jet” and “Back-to-Back” events compared with the average maximum pT particle, PTmax, in “min-bias” collisions (pT > 0.5 GeV/c, |h| < 1). ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 21 Min-Bias “Associated” Highest pT charged particle! Charged Particle Density “Associated” densities do not include PTmax! Charged Particle Density: dN/dhd PTmax Direction 0.5 Correlations in Charged Particle Density CDF Preliminary Associated Density PTmax not included data uncorrected 0.4 Charge Density 0.3 0.2 0.1 Charged Particles (|h|<1.0, PT>0.5 GeV/c) PTmax Min-Bias 0.0 0 30 60 90 120 150 180 210 240 270 300 330 360 (degrees) Use the maximum pT charged particle in the event, PTmax, to define a direction and look at the the “associated” density, dNchg/dhd. Shows the data on the dependence of the “associated” charged particle density, dNchg/dhd, 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/dhd, for “min-bias” events. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 22 Min-Bias “Associated” Rapid rise in the particle density in the “transverse” region as PTmax increases! Charged Particle Density Associated Particle Density: dN/dhd PTmaxDirection Direction PTmax 1.0 “Toward” “Transverse” “Transverse” Correlations in “Away” Associated Particle Density Jet #1 PTmax > 2.0 GeV/c PTmax > 1.0 GeV/c 0.8 Charged Particles (|h|<1.0, PT>0.5 GeV/c) CDF Preliminary data uncorrected PTmax > 0.5 GeV/c Transverse Region 0.6 Transverse Region 0.4 0.2 Jet #2 PTmax PTmax not included Min-Bias 0.0 0 30 60 90 120 150 180 210 240 270 300 330 360 (degrees) Ave Min-Bias 0.25 per unit h- Shows the data on the dependence of the “associated” charged particle density, dNchg/dhd, 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!). ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 23 Back-to-Back “Associated” Charged Particle Densities Maximum pT particle in the “transverse” region! Jet #1 Direction PTmaxT Direction “Associated” densities do not include PTmaxT! “Toward” “TransMAX” PTmaxT “TransMIN” PTmaxT Direction Jet#1 Region Jet#2 Region Jet#1 Region Jet#2 Region “Away” Jet #2 Direction Use the leading jet in “back-to-back” events to define the “transverse” region and look at the maximum pT charged particle in the “transverse” region, PTmaxT. Look at the dependence of the “associated” charged particle and PTsum densities, dNchg/dhd and dPTsum/dhd for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmaxT) relative to PTmaxT. Rotate so that PTmaxT is at the center of the plot (i.e. 180o). ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 24 Back-to-Back “Associated” Charged Particle Density “Associated” densities do not include PTmaxT! PTmaxT Direction Jet #1 Jet#1 Region Associated Particle Density Jet #2 Charged Particles (|h|<1.0, PT>0.5 GeV/c) CDF Preliminary Jet #3 Jet#2 Region Associated Particle Density: dN/dhd 10.0 data uncorrected Back-to-Back 30 < ET(jet#1) < 70 GeV PTmaxT not included 1.0 Jet#2 Region PTmaxT > 2.0 GeV/c PTmaxT > 1.0 GeV/c Jet #4?? "Jet#1" Region PTmaxT PTmaxT > 0.5 GeV/c 0.1 0 30 60 90 120 150 180 210 240 270 300 330 360 (degrees) Log Scale! Look at the dependence of the “associated” charged particle density, dNchg/dhd for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmaxT) relative to PTmaxT (rotated to 180o) for PTmaxT > 0.5 GeV/c, PTmaxT > 1.0 GeV/c and PTmaxT > 2.0 GeV/c, for “back-to-back” events with 30 < ET(jet#1) < 70 GeV . Shows “jet structure” in the “transverse” region (i.e. the “birth” of the 3rd & 4th jet). ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 25 “Back-to-Back” “Associated” Density “Back-to-Back” vs “MinBias” “Birth” ofCharge jet#3 in the “Associated” Density “transverse” region! PTmaxT Direction Associated Particle Density: dN/dhd “Min-Bias” “Associated” Density Associated Particle Density Jet#2 Region 10.0 Jet#1 Region PTmax Direction PTmaxT > 2.0 GeV/c PTmax > 2.0 GeV/c Charged Particles Particles Charged (|h|<1.0, PT>0.5 PT>0.5 GeV/c) GeV/c) (|h|<1.0, 3030< <ET(jet#1) ET(jet#1)< <7070GeV GeV 1.0 Min-Bias x 1.65 PTmaxT PTmaxT PTmax PTmax Min-Bias PTmaxT, PTmaxT,PTmax PTmaxnot notincluded included CDFPreliminary Preliminary CDF data uncorrected data uncorrected 0.1 Correlations in 0 30 60 90 120 150 180 210 240 270 300 330 360 (degrees) Log Scale! “Birth” of jet#1 in Shows the dependence of the “associated” charged particle density,“min-bias” dNchg/dhd for collisions! pT > 0.5 GeV/c, |h| < 1 (not including PTmaxT) relative to PTmaxT (rotated to 180o) for PTmaxT > 2.0 GeV/c, for “back-to-back” events with 30 < ET(jet#1) < 70 GeV. Shows the data on the dependence of the “associated” charged particle density, dNchg/dhd, pT > 0.5 GeV/c, |h| < 1 (not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” events with PTmax > 2.0 GeV/c. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 27 Jet Topologies QCDThree Four Jet QCD Jet Topology Topology Charged Particle Density: dN/dhd QCD 2-to-4 Scattering Multiple Parton Interactions 2 Preliminary CDF Final-State Jet #1 data uncorrected Radiation Outgoing Parton 346 10 14 30 < ET(jet#1) < 70 GeV Outgoing Parton Outgoing PartonBack-to-Back 18 30 34 38 326 42 322 46 318 Jet #1 PT(hard) 50 54 Jet#1 306 58 PT(hard) 302 298 PTmaxT Proton Direction Proton 6 358 26 330 310 Jet #3 354 22 334 314 Jet#1 Region 350 342 338 62 66 70 294 Jet #4 74 290 78 286 Jet #4 AntiProton AntiProton "Transverse" Jet #3 Region 282 278 274 Jet#2 Region Underlying Event Underlying Event PTmaxT 270 86 90 94 98 266 Underlying Event 102 262 Jet #2 0.5 258 Underlying Event 106 254 110 Jet #2 250 114 1.0 246 118 126 238 1.5 234 230 130 134 138 226 Particles ChargedFinal-State GeV/c) (|h|<1.0, PT>0.5 Radiation Associated Density PTmaxT > 2 GeV/c (not included) 142 222 2.0 218 214 146 150 154 210 Polar Plot Initial-State Radiation 122 242 82 "Transverse" Region 158 206 162 202 198 194 190 178 186 174 170 166 182 Parton Outgoing Outgoing Shows the dependence ofParton the “associated” charged particleOutgoing density,Parton dNchg/dhd, pT > 0.5 GeV/c, |h| < 1, PTmaxT > 2.0 GeV/c (not including PTmaxT) relative to PTmaxT (rotated to 180o) and the charged particle density, dNchg/dhd, pT > 0.5 GeV/c, |h| < 1, relative to jet#1 (rotated to 270o) for “back-to-back events” with 30 < ET(jet#1) < 70 GeV. ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 29 “Associated” PTsum Density PYTHIA Tune A vs HERWIG HERWIG (without multiple parton interactions) does not produce enough “associated” PTsum in the direction of PTmaxT! Associated PTsum Density: dPT/dhd PTmaxT > 0.5 GeV/cAssociated PTsum Density: dPT/dhd 10.0 Associated PTsum Density (GeV/c) Associated PTsum Density (GeV/c) 10.0 Charged Particles (|h|<1.0, PT>0.5 GeV/c) PTmaxT not included 1.0 PTmaxT > 0.5 GeV/c Back-to-Back 30 < ET(jet#1) < 70 GeV PY Tune A CDF Preliminary PTmaxT data uncorrected theory + CDFSIM "Jet#1" Region 0.1 Charged Particles (|h|<1.0, PT>0.5 GeV/c) PTmaxT not included 1.0 PTmaxT > 0.5 GeV/c HERWIG CDF Preliminary 30 60 90 120 150 180 210 240 270 300 330 360 0 30 60 90 120 (degrees) "Jet#1" Region 2 CDF Preliminary And HERWIG (without multiple parton interactions) does not 2 Charged Particles produceBack-to-Back enough PTsum in the (|h|<1.0, PT>0.5 GeV/c) 30 < ET(jet#1) < 70 GeV direction opposite of PTmaxT!1 PTmaxT not included PYTHIA Tune A Data - Theory (GeV/c) data uncorrected theory + CDFSIM 150 180 210 240 270 300 330 360 (degrees) Data - Theory: Associated PTsum Density dPT/dhd Data - Theory: Associated PTsum Density dPT/dhd Data - Theory (GeV/c) PTmaxT data uncorrected theory + CDFSIM 0.1 0 1 Back-to-Back 30 < ET(jet#1) < 70 GeV 0 -1 PTmaxT CDF Preliminary data uncorrected theory + CDFSIM Charged Particles (|h|<1.0, PT>0.5 GeV/c) Back-to-Back 30 < ET(jet#1) < 70 GeV PTmaxT not included 0 -1 PTmaxT HERWIG "Jet#1" Region "Jet#1" Region -2 -2 0 30 60 90 120 150 180 210 240 270 300 330 360 0 30 90 120 150 180 210 240 270 300 330 360 (degrees) (degrees) ISMD2004 July 27, 2004 60 Rick Field - Florida/CDF Page 31 “Associated” PTsum Density PYTHIA Tune A vs HERWIG For PTmaxT > 2.0 GeV both PYTHIA and HERWIG produce slightly too much “associated” PTsum in the direction of PTmaxT! PTmaxT > 2 GeV/c Associated PTsum Density: dPT/dhd Associated PTsum Density: dPT/dhd 10.0 Charged Particles (|h|<1.0, PT>0.5 GeV/c) PTmaxT not included Associated PTsum Density (GeV/c) Associated PTsum Density (GeV/c) 10.0 1.0 PTmaxT > 2.0 GeV/c Back-to-Back 30 < ET(jet#1) < 70 GeV PY Tune A CDF Preliminary PTmaxT data uncorrected theory + CDFSIM "Jet#1" Region 0.1 Charged Particles (|h|<1.0, PT>0.5 GeV/c) PTmaxT not included 1.0 PTmaxT > 2.0 GeV/c CDF Preliminary PTmaxT data uncorrected theory + CDFSIM "Jet#1" Region 0.1 0 30 60 90 120 150 180 210 240 270 300 330 360 0 30 60 90 120 (degrees) CDF Preliminary 240 270 300 330 360 Data - Theory PTmaxT 0 Charged Particles (|h|<1.0, PT>0.5 GeV/c) "Jet#1" Region PTmaxT > 2.0 GeV/c (not included) Back-to-Back 30 < ET(jet#1) < 70 GeV HERWIG data uncorrected theory + CDFSIM -1 Charged Particles (|h|<1.0, PT>0.5 GeV/c) 210 Data - Theory: Associated Particle Density dN/dhd 1 0.0 -1.0 180 2 PYTHIA Tune A theory + CDFSIM 1.0 150 (degrees) But HERWIG (without multiple Data - Theory: Associated Particleinteractions) Density dN/dhd parton produces too few particles in the Back-to-Back CDF Preliminary direction opposite of PTmaxT! 30 < ET(jet#1) < 70 GeV data uncorrected 2.0 Data - Theory Back-to-Back 30 < ET(jet#1) < 70 GeV HERWIG PTmaxT "Jet#1" Region PTmaxT > 2.0 GeV/c (not included) -2.0 -2 0 30 60 90 120 150 180 210 240 270 300 330 360 0 30 (degrees) ISMD2004 July 27, 2004 60 90 120 150 180 210 240 270 300 330 360 (degrees) Rick Field - Florida/CDF Page 33 Summary “Leading Jet” Jet #1 Direction Jet #1 Direction “Back-to-Back” “Toward” “Toward” “Trans 1” “Trans 1” “Trans 2” “Trans 2” “Away” “Away” Jet #2 Direction There are some interesting correlations between the “transverse 1” and “transverse 2” regions both for “Leading-Jet” and “Back-to-Back” events! PYTHIA Tune A (with multiple parton scattering) does a much better job in describing these correlations than does HERWIG (without multiple parton scattering). Question: Is this a probe of multiple parton interactions? ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 34 Summary “Leading Jet” Jet #1 Direction Jet #1 Direction “Back-to-Back” “Toward” “Toward” “Transverse” “Transverse” “Transverse” “Transverse” “Away” “Away” Jet #2 Direction “Back-to-Back” events have less “hard scattering” (initial and final state radiation) component in the “transverse” region which allows for a closer look at the “beam-beam remnant” and multiple parton scattering component of the “underlying” event. PYTHIA Tune A (with multiple parton scattering) does a much better job in describing the “back-to-back” events than does HERWIG (without multiple parton scattering). ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 35 Summary Max pT in the “transverse” region! “Associated” densities do not include PTmaxT! Jet #1 Direction PTmaxT Direction PTmax Direction “Toward” “TransMAX” “TransMIN” Jet#2 Region Jet#1 Region Next Step Correlations in Look at the jet topologies Jet #2 Direction (2 jet vs 3 jet vs 4 jet etc). The “associated” densities strong correlations Seeshow if there is an excess of(i.e. jet structure) in the “transverse” region both for “Leading Jet” and “Back-to-Back” events. 4 jet events due to multiple interactions! The “birth” of the 1st jet inparton “min-bias” collisions looks very similar to the PTmaxT “Away” “birth” of the 3rd jet in the “transverse” region of hard scattering “Back-toBack” events. Question: Is the topology 3 jet or 4 jet? ISMD2004 July 27, 2004 Rick Field - Florida/CDF Page 36