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. LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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. LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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. LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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) LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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. LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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 LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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 LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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. LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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. LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

Drell-Yan Production at CMS Lepton-Pair Transverse Momentum Squared <(PT)2(pair)> versus M(pair) The lepton-pair <(PT)2> much larger at the LHC! Z Z Shows the lepton-pair average (PT)2 versus the lepton-pair invariant mass at 1.96 TeV for PYTHIA Tune AW and HERWIG. Shows the lepton-pair average (PT)2 versus the lepton-pair invariant mass at 14 TeV for PYTHIA Tune AW and HERWIG. LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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). LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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). LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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). LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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). LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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). LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

The “Underlying Event” Drell-Yan vs Jets at CDF The “Underlying Event” in High PT Lepton-Pair and Jet Production Drell-Yan “Leading Jet” LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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). LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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).. LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

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). LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

The “Underlying Event” Drell-Yan vs Jets at CMS The “Underlying Event” in High PT Lepton-Pair and Jet Production Drell-Yan “Leading Jet” LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

UE&MB@CMS UE&MB@CMS Measure Min-Bias and the “Underlying Event” at CMS 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) Khristian Kotov (UF Student, Acosta) Me at CMS! Measure Min-Bias and the “Underlying Event” at CMS The plan involves two phases. Phase 1 would be to measure min-bias and the “underlying event” as soon as possible (when the luminosity is low), perhaps during commissioning. We would then tune the QCD Monte-Carlo models for all the other CMS analyses. Phase 1 would be a service to the rest of the collaboration. As the measurements become more reliable we would re-tune the QCD Monte-Carlo models if necessary and begin Phase 2. Phase 2 is “physics” and would include comparing the min-bias and “underlying event” measurements at the LHC with the measurements we have done (and am doing now) at CDF and then writing a physics publication. Darin LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF

Rick Field - Florida/CMS/CDF UE&MB@CMS 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). LPC Physics Group December 15, 2005 Rick Field - Florida/CMS/CDF