1. CDF Joint Physics Group June 27, 2003 Rick FieldPage 1 PYTHIA Tune A versus Run 2 Data  Compare PYTHIA Tune A with Run 2 data on the “underlying event”. Outline of Talk  Compare PYTHIA Tune A with the properties of the “calorimeter jets” as measured in Run 2.  Use PYTHIA Tune A to correct the Run 2 data from measured to “true”.  Compare PYTHIA Tune A before and after CDFSIM. Construct “correction factors”! JetClu R = 0.7

2. CDF Joint Physics Group June 27, 2003 Rick FieldPage 2 “Underlying Event” as defined by “Charged particle Jets”  Look at charged particle correlations in the azimuthal angle  relative to the leading charged particle jet.  Define |  | 120 o as “Away”.  All three regions have the same size in  -  space,  x  = 2x120 o = 4  /3. Charged Particle  Correlations P T > 0.5 GeV/c |  | < 1 Toward-side “jet” (always) Away-side “jet” (sometimes) Perpendicular to the plane of the 2-to-2 hard scattering “Transverse” region is very sensitive to the “underlying event”! Look at the charged particle density in the “transverse” region!

3. CDF Joint Physics Group June 27, 2003 Rick FieldPage 3 Tuned PYTHIA 6.206 Run 1 Tune A  Compares the average “transverse” charge particle density (|  | 0.5 GeV) versus P T (charged jet#1) and the P T distribution of the “transverse” and “Min-Bias” densities with the QCD Monte-Carlo predictions of a tuned version of PYTHIA 6.206 (P T (hard) > 0, CTEQ5L, Set A). Set A Min-Bias = 0.24 Describes “Min-Bias” collisions! Describes the “underlying event”! “Min-Bias” Set A P T (charged jet#1) > 30 GeV/c “Transverse” = 0.60 Describes the rise from “Min-Bias” to “underlying event”!

4. CDF Joint Physics Group June 27, 2003 Rick FieldPage 4 “Transverse” Charged Particle Density “Transverse” Charged Particle Density  Shows the data on the average “transverse” charge particle density (|  | 0.5 GeV) as a function of the transverse momentum of the leading charged particle jet from Run 1.  Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1. The errors on the (uncorrected) Run 2 data include both statistical and correlated systematic uncertainties. “Transverse” region as defined by the leading “charged particle jet” Excellent agreement between Run 1 and 2! PYTHIA Tune A was tuned to fit the “underlying event” in Run I!  Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after CDFSIM).

5. CDF Joint Physics Group June 27, 2003 Rick FieldPage 5 “Transverse” Charged PTsum Density “Transverse” Charged PTsum Density  Shows the data on the average “transverse” charged PTsum density (|  | 0.5 GeV) as a function of the transverse momentum of the leading charged particle jet from Run 1.  Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1. The errors on the (uncorrected) Run 2 data include both statistical and correlated systematic uncertainties. “Transverse” region as defined by the leading “charged particle jet” Excellent agreement between Run 1 and 2!  Shows the prediction of PYTHIA Tune A at 1.96 TeV after detector simulation (i.e. after CDFSIM). PYTHIA Tune A was tuned to fit the “underlying event” in Run I!

6. CDF Joint Physics Group June 27, 2003 Rick FieldPage 6 “Underlying Event” as defined by “Calorimeter Jets”  Look at charged particle correlations in the azimuthal angle  relative to the leading JetClu jet.  Define |  | 120 o as “Away”.  All three regions have the same size in  -  space,  x  = 2x120 o = 4  /3. Charged Particle  Correlations P T > 0.5 GeV/c |  | < 1 Away-side “jet” (sometimes) Perpendicular to the plane of the 2-to-2 hard scattering “Transverse” region is very sensitive to the “underlying event”! Look at the charged particle density in the “transverse” region!

7. CDF Joint Physics Group June 27, 2003 Rick FieldPage 7 “Transverse” Charged Particle Density  Shows the data on the average “transverse” charge particle density (|  | 0.5 GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |  (jet)| < 2) from Run 2.  Compares the “transverse” region of the leading “charged particle jet”, chgjet#1, with the “transverse” region of the leading “calorimeter jet” (JetClu R = 0.7), jet#1., compared with PYTHIA Tune A after CDFSIM. “Transverse” region as defined by the leading “calorimeter jet”

8. CDF Joint Physics Group June 27, 2003 Rick FieldPage 8 “Transverse” Charged PTsum Density  Shows the data on the average “transverse” charged PTsum density (|  | 0.5 GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |  (jet)| < 2) from Run 2.  Compares the “transverse” region of the leading “charged particle jet”, chgjet#1, with the “transverse” region of the leading “calorimeter jet” (JetClu R = 0.7), jet#1., compared with PYTHIA Tune A after CDFSIM. “Transverse” region as defined by the leading “calorimeter jet”

9. CDF Joint Physics Group June 27, 2003 Rick FieldPage 9 “Transverse” Charged Particle Density  Shows the data on the average “transverse” charge particle density (|  | 0.5 GeV) as a function of the transverse energy of the leading JetClu jet (R = 0.7, |  (jet)| < 2) from Run 2.  Shows the generated prediction of PYTHIA Tune A before CDFSIM., compared with PYTHIA Tune A after CDFSIM. “Transverse” region as defined by the leading “calorimeter jet”  Shows the ratio CDFSIM/Generated for PYTHIA Tune A. Small correction (about 10%) independent of E T (jet#1)!

10. CDF Joint Physics Group June 27, 2003 Rick FieldPage 10 The Leading “Charged Particle” Jet  Shows the data on the average number of charged particles within the leading “charged particle jet” (|  | 0.5 GeV, R = 0.7) as a function of the transverse momentum of the leading “charged particle jet” from Run 1.  Compares the Run 2 data (Min-Bias, JET20, JET50, JET70, JET100) with Run 1. The errors on the (uncorrected) Run 2 data include both statistical and correlated systematic uncertainties. Excellent agreement between Run 1 and 2! PYTHIA produces too many charged particles in the leading “charged particle jet”!

11. CDF Joint Physics Group June 27, 2003 Rick FieldPage 11 The Leading “Calorimeter” Jet  Shows the Run 2 data on the average number of charged particles (|  | 0.5 GeV, R = 0.7) within the leading “calorimeter jet” (JetClu R = 0.7, |  (jet)|< 0.7) as a function of the transverse energy of the leading “calorimeter jet”.  Compares the number of charged particles within the leading “charged particle jet”, chgjet#1, with the number of charged particles within the leading “calorimeter jet” (JetClu R = 0.7), jet#1. PYTHIA produces too many charged particles in the leading “calorimeter jet”!

12. CDF Joint Physics Group June 27, 2003 Rick FieldPage 12 The Leading “Calorimeter” Jet Charged Particle Multiplicity  Shows the Run 2 data on the average number of charged particles (|  | 0.5 GeV, R = 0.7) within the leading “calorimeter jet” (JetClu R = 0.7, |  (jet)|< 0.7) as a function of E T (jet#1) compared with PYTHIA Tune A after CDFSIM.  Shows the generated prediction of PYTHIA Tune A before CDFSIM.  Shows the ratio CDFSIM/Generated for PYTHIA Tune A. Correction becomes large for E T (jet#1) > 100 GeV and depends on E T (jet#1)!  Shows “corrected” Run 2 data compared with PYTHIA Tune A (uncorrected). Multiply data by the “unfolding function” (i.e. Generated/CDFSIM) determined from PYTHIA Tune A to get “corrected” data.

13. CDF Joint Physics Group June 27, 2003 Rick FieldPage 13 The Leading “Calorimeter” Jet Charged P T Distribution  Shows the transverse momentum distribution of charged particles (|  |<1) within the leading “charged particle jet” compared with PYTHIA Tune A. The plot shows dN chg /dz with z = P T /P T (chgjet#1) for the range 30 < P T (chgjet#1) < 70 GeV/c.  Shows the transverse momentum distribution of charged particles (|  |<1) within the leading “calorimeter jet” (JetClu, R = 0.7, |  (jet)| < 0.7) compared with PYTHIA Tune A. The plot shows dN chg /dz with z = P T /E T (jet#1) for the range 30 < E T (jet#1) < 70 GeV. PYTHIA produces too many “soft” charged particles within the leading “jet”! The integral of F(z) is the average number of charged particles within the leading “charged particle jet”. PYTHIA produces too many “soft” charged particles within the leading “jet”!

14. CDF Joint Physics Group June 27, 2003 Rick FieldPage 14 The Leading “Calorimeter” Jet Charged PT sum & PT max Fraction  Shows average charged PTsum fraction, PTsum/E T (jet#1), and the average charged PTmax fraction, PTmax/E T (jet#1), within the leading “calorimeter jet” (JetClu, R = 0.7, |  (jet)| < 0.7) compared with PYTHIA Tune A.  Shows distribution of the charged PTsum fraction, z = PTsum/E T (jet#1), and the distribution of charged PTmax fraction, z = PTmax/E T (jet#1), within the leading “calorimeter jet” (JetClu, R = 0.7, |  (jet)| < 0.7) for the range 95 < E T (jet#1) < 130 GeV compared with PYTHIA Tune A. PYTHIA does okay on the charged PTmax fraction! But PYTHIA does not do well on the charged PTsum fraction! But PYTHIA does not do as well on the charged PTsum fraction!

15. CDF Joint Physics Group June 27, 2003 Rick FieldPage 15 The Leading “Calorimeter” Jet Charged PT sum Fraction  Shows average charged PTsum fraction, PTsum/E T (jet#1), within the leading “calorimeter jet” (JetClu, R = 0.7, |  (jet)| < 0.7) compared with PYTHIA Tune A after CDFSIM.  Shows the generated prediction of PYTHIA Tune A before CDFSIM.  Shows the ratio CDFSIM/Generated for PYTHIA Tune A. Very large correction that depends on E T (jet#1)!  Shows “corrected” Run 2 data compared with PYTHIA Tune A (uncorrected). Multiply data by the “unfolding function” (i.e. Generated/CDFSIM) determined from PYTHIA Tune A to get “corrected” data.

16. CDF Joint Physics Group June 27, 2003 Rick FieldPage 16 Proton-AntiProton Collisions  Draw an R = 0.7 cone around the leading calorimeter jet (JetClu, R = 0.7).  Look at charged particles within R = 0.7 of the leading calorimeter jet. Momentum perpendicular to the jet axis Momentum perpendicular to the beam axis

17. CDF Joint Physics Group June 27, 2003 Rick FieldPage 17 The Leading “Calorimeter” Jet Charged K T Distribution  Shows the average momentum perpendicular to the jet axis for charged particles (P T > 0.5 GeV/c, |  |<1) within the leading “calorimeter jet” (JetClu, R = 0.7) compared with PYTHIA Tune A.  Shows the distribution of momentum perpendicular to the jet axis for charged particles within the leading “calorimeter jet” compared with PYTHIA Tune A. The plot shows dN chg /dK T for the range 30 < E T (jet#1) < 70 GeV and 95 < E T (jet#1) < 130 GeV. Increases as E T (jet#1) increases!

18. CDF Joint Physics Group June 27, 2003 Rick FieldPage 18 Inclusive Jet Cross Section  Shows the uncorrected inclusive “calorimeter jet” cross-section for (JetClu, R = 0.7, energy scale factor of 1.042) compared with PYTHIA Tune A (after CDFSIM).  Shows the ratio of the uncorrected inclusive “calorimeter jet” cross-section for (JetClu, R = 0.7, energy scale factor of 1.042) to PYTHIA Tune A (after CDFSIM). Very similar to Frank Chlebana’s “corrected” plots! Data and theory are normalized to agree at this one point. This fixes the normalization for all the other plots presented in this talk!

19. CDF Joint Physics Group June 27, 2003 Rick FieldPage 19 Inclusive Cross-Section “Correction Factors”  Shows PYTHIA Tune A + CDFSIM inclusive “calorimeter jet” cross-section for (JetClu, R = 0.7) compared with the “true” cross-section where “true” is the PT sum of all hadrons (partons) with P T > 0 in R = 0.7 cone around JetClu. Measured “True” Correction factors! “True”

20. CDF Joint Physics Group June 27, 2003 Rick FieldPage 20 Jet Cross Sections  Shows the Run 2 uncorrected inclusive “calorimeter jet” cross-section and the leading “calorimeter jet” cross-section (JetClu, R = 0.7, energy scale factor of 1.042).  Shows the ratio of the leading jet cross section to the inclusive jet cross-section for (JetClu, R = 0.7, energy scale factor of 1.042) compared with PYTHIA Tune A (after CDFSIM). Measures how much cross-section comes from >1 jet!

21. CDF Joint Physics Group June 27, 2003 Rick FieldPage 21 Jet Cross Sections  Shows the uncorrected inclusive jet cross-section for (JetClu, R = 0.7, energy scale factor of 1.042) compared with PYTHIA Tune A (after CDFSIM).  Shows the ratio of the uncorrected inclusive jet cross-section for (JetClu, R = 0.7, energy scale factor of 1.042) to PYTHIA Tune A (after CDFSIM). Tansverse momentum of the hard 2-to-2 parton-parton collision!

22. CDF Joint Physics Group June 27, 2003 Rick FieldPage 22 Leading “Charged Particle Jet” Cross Section  Shows the uncorrected leading “charged particle jet” cross-section for (P T > 0.5 GeV/c, |  |<1) compared with PYTHIA Tune A (after CDFSIM).  Shows the ratio of the uncorrected leading “charged particle jet” cross-section for (P T > 0.5 GeV/c, |  |<1) to PYTHIA Tune A (after CDFSIM). Compares data/theory for the leading charged particle jet and the leading calorimeter jet!

23. CDF Joint Physics Group June 27, 2003 Rick FieldPage 23 Summary & Conclusions PYTHIA Tune A  PYTHIA Tune A does a good job of describing the “underlying event” in the Run 2 data as defined by “charged particle jets” and as defined by “calorimeter jets”. HERWIG Run 2 comparisons will be coming soon!  PYTHIA Tune A does a fairly good job (although not perfect) describing the properties of the “calorimeter jets” in Run 2 (in the central region!).  I am hoping we can use the QCD Monte-Carlo models (PYTHIA & HERWIG) to correct the data from measured to “true” by constructing “correction factors” for every observable of interest. This is a different method from the “jet energy corrections” used in Run 1!