1. The “Underlying Event” CDF-LHC Comparisons
Outline of Talk
Jet Production: The “underlying event” in high pT jet production in Run 2 at CDF.
PT(Z-boson): Tuning to fit the PT(Z) distribution in Run 2 at CDF.
Great process to study the “underlying event”!
Drell-Yan: The “underlying event” in Drell-Yan production in Run 2 at CDF.
Extrapolations to the LHC: The “underlying event” in high pT jet production and Drell-Yan at CMS.
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

2. The “Transverse” Region as defined by the Leading Jet
Look at the charged particle density and the ETsum density in the “transverse” region!
“Transverse” region is very sensitive to the “underlying event”!
Charged Particles (pT > 0.5 GeV/c, |h| < 1)
Calorimeter Towers (ET > 0.1 GeV, |h| < 1)
Look at the “transverse” region as defined by the leading calorimeter jet (MidPoint, R = 0.7, fmerge = 0.75, |h| < 2).
Define |Df| < 60o as “Toward”, 60o < -Df < 120o and 60o < Df < 120o as “Transverse 1” and “Transverse 2”, and |Df| > 120o as “Away”. Each of the two “transverse” regions have area DhDf = 2x60o = 4p/6. The overall “transverse” region is the sum of the two transverse regions (DhDf = 2x120o = 4p/3).
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, by dividing by the area in h-f space.
Study the calorimeter towers (ET > 0.1 GeV, |h| < 1) and form the scalar ET sum density, dETsum/dhdf.
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

3. The “Transverse” Region as defined by the Leading Jet
Look at the charged particle density and the ETsum density in the “transverse” region!
“Transverse” region recieves contributions from initial & final-state radiation!
Charged Particles (pT > 0.5 GeV/c, |h| < 1)
Calorimeter Towers (ET > 0.1 GeV, |h| < 1)
Look at the “transverse” region as defined by the leading calorimeter jet (MidPoint, R = 0.7, fmerge = 0.75, |h| < 2).
Define |Df| < 60o as “Toward”, 60o < -Df < 120o and 60o < Df < 120o as “Transverse 1” and “Transverse 2”, and |Df| > 120o as “Away”. Each of the two “transverse” regions have area DhDf = 2x60o = 4p/6. The overall “transverse” region is the sum of the two transverse regions (DhDf = 2x120o = 4p/3).
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, by dividing by the area in h-f space.
Study the calorimeter towers (ET > 0.1 GeV, |h| < 1) and form the scalar ET sum density, dETsum/dhdf.
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

4. The “Underlying Event” in High PT Jet Production (CDF)
HERWIG (without MPI) lies below the data for PT(jet#1) < 200 GeV/c!
“Transverse” <Densities> vs PT(jet#1)
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

5. The “Central” Region in Drell-Yan Production
Look at the charged particle density and the ETsum density in the “central” region!
Charged Particles (pT > 0.5 GeV/c, |h| < 1)
Calorimeter Towers (ET > 0.1 GeV, |h| < 1)
After removing the lepton-pair everything else is the “underlying event”!
Look at the “central” region after removing the lepton-pair.
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, by dividing by the area in h-f space.
Study the calorimeter towers (ET > 0.1 GeV, |h| < 1) and form the scalar ET sum density, dETsum/dhdf.
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

6. Rick Field - Florida/CMS/CDF
CDF Run 1 PT(Z)
PYTHIA 6.2 CTEQ5L
UE Parameters
Parameter
Tune A
Tune A25
Tune A50
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(67)
4.0
MSTP(91)
PARP(91)
1.0
2.5
5.0
PARP(93)
15.0
25.0
ISR Parameter
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), Tune A25 (<pT(Z)> = 10.1 GeV/c), and Tune A50 (<pT(Z)> = 11.2 GeV/c).
Intrensic KT
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

7. CDF Run 1 PT(Z) 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 AW (<pT(Z)> = 11.7 GeV/c).
Effective Q cut-off, below which space-like showers are not evolved.
The Q2 = kT2 in as for space-like showers is scaled by PARP(64)!
Intrensic KT
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

8. Drell-Yan Production at CDF
Lepton-Pair Transverse Momentum
<PT(pair)> versus M(pair) Z Z
Shows the lepton-pair average PT versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and PYTHIA Tune A.
Shows the lepton-pair average PT versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG.
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

9. Drell-Yan Production at CMS
Lepton-Pair Transverse Momentum
<PT(pair)> versus M(pair)
The lepton-pair <PT> much larger at the LHC! Z Z
Shows the lepton-pair average PT versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG.
Shows the lepton-pair average PT versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG.
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

10. The “Underlying Event” in Drell-Yan Production (CDF)
Charged particle density versus M(pair)
HERWIG (without MPI) is much less active than PY Tune AW (with MPI)! Z Z
Shows the charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and PYTHIA Tune A.
Shows the charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG (with no MPI).
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

11. The “Underlying Event” in Drell-Yan Production (CMS)
Charged particle density versus M(pair)
HERWIG (without MPI) is much less active than PY Tune AW (with MPI)!
“Underlying event” much more active at the LHC! Z
Charged particle density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG (without MPI).
Charged particle density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG (without MPI).
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

12. The “Underlying Event” in Drell-Yan Production (CDF)
Charged PTsum density versus M(pair)
HERWIG (without MPI) is much less active than PY Tune AW (with MPI)! Z
Shows the charged PTsum density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and PYTHIA Tune A.
Shows the charged PTsum density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG (without MPI).
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

13. The “Underlying Event” in Drell-Yan Production (CMS)
Charged PTsum density versus M(pair)
HERWIG (without MPI) is much less active than PY Tune AW (with MPI)!
“Underlying event” much more active at the LHC! Z
Charged PTsum density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG (without MPI).
Charged PTsum density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG (without MPI).
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

14. The “Underlying Event” in Drell-Yan Production (CMS)
ETsum density versus M(pair) Z Z
ETsum density versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG (without MPI).
ETsum density versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG (without MPI).
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

15. The “Underlying Event” Drell-Yan vs Jets at CDF
The “Underlying Event” in High PT Lepton-Pair and Jet Production
Drell-Yan
“Leading Jet”
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

16. The “Underlying Event” in High PT Jet Production (CMS)
Charged particle density versus PT(jet#1)
The “Underlying Event”
“Underlying event” much more active at the LHC!
Charged particle density in the “Transverse” region versus PT(jet#1) at 1.96 TeV for PY Tune AW and HERWIG (without MPI).
Charged particle density in the “Transverse” region versus PT(jet#1) at 14 TeV for PY Tune AW and HERWIG (without MPI).
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

17. The “Underlying Event” in High PT Jet Production (CMS)
Charged PTsum density versus PT(jet#1)
The “Underlying Event”
“Underlying event” much more active at the LHC!
Charged PTsum density in the “Transverse” region versus PT(jet#1) at 1.96 TeV for PY Tune AW and HERWIG (without MPI).
Charged PTsum density in the “Transverse” region versus PT(jet#1) at 14 TeV for PY Tune AW and HERWIG (without MPI)..
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

18. The “Underlying Event” in High PT Jet Production (CMS)
ETsum density versus PT(jet#1)
“Underlying event” much more active at the LHC!
ETsum density in the “Transverse” region versus PT(jet#1) at 1.96 TeV for PY Tune AW and HERWIG (without MPI).
ETsum density in the “Transverse” region versus PT(jet#1) at 14 TeV for PY Tune AW and HERWIG (without MPI).
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

19. The “Underlying Event” Drell-Yan vs Jets at CMS
The “Underlying Event” in High PT Lepton-Pair and Jet Production
Drell-Yan
“Leading Jet”
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

20. Rick Field - Florida/CMS/CDF
Min-Bias Studies: Charged particle distributions and correlations. Construct “charged particle jets” and look at “mini-jet” structure and the onset of the “underlying event”. (requires only charged tracks)
“Underlying Event” Studies: The “transverse region” in “leading Jet” and “back-to-back” jet production. The “central region” in Drell-Yan production. (requires charged tracks and calorimeter and muons for Drell-Yan)
Drell-Yan Studies: Transverse momentum distribution of the lepton-pair versus the mass of the lepton-pair, <pT(pair)>, <pT2(pair)>, ds/dpT(pair) (only requires muons). Event structure for large lepton-pair pT (i.e. mm +jets, requires muons and calorimeter).
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF

21.
Min-Bias Studies: Charged particle distributions and correlations. Construct “charged particle jets” and look at “mini-jet” structure and the onset of the “underlying event”. (requires only charged tracks)
Rick Field (Florida)
Darin Acosta (Florida)
Albert De Roeck (CERN)
Paolo Bartalini (UF Postdoc at CERN)
Livio Fano' (INFN/Perugia at CERN)
Filippo Ambroglini (INFN/Perugia at CERN)
“Underlying Event” Studies: The “transverse region” in “leading Jet” and “back-to-back” jet production. The “central region” in Drell-Yan production. (requires charged tracks and calorimeter and muons for Drell-Yan)
Drell-Yan Studies: Transverse momentum distribution of the lepton-pair versus the mass of the lepton-pair, <pT(pair)>, <pT2(pair)>, ds/dpT(pair) (only requires muons). Event structure for large lepton-pair pT (i.e. mm +jets, requires muons and calorimeter).
LHC/CMS Journal Club November 30, 2005
Rick Field - Florida/CMS/CDF