studying the “underlying event” at cdf

Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 1 “Leading Jet” vs Z-Boson Studying the Studying the “ “ Underlying Event Underlying Event ” ” at CDF at CDF Proton AntiProton PT(hard) Outgoing Parton Outgoing Parton Underlying Event Underlying Event Initial-State Radiation Final-State Radiation Rick Field University of Florida Outline of Talk CDF Run 2 Proton AntiProton Drell-Yan Production Anti - Lepton Lepton Underlying Even t Un derlying Event ¨ The “Towards”, “Away”, and “Transverse” regions of η-φ space. ¨ Four Jet Topologies. ¨ The “transMAX” and “transMIN” regions. ¨ The observables: First look at average quantities. Then do distributions. ¨ Look at <p T > versus Nchg in “min-bias” and Drell-Yan. ¨ The “underlying event” in Drell-Yan production. “Leading Jet” ¨ Show some extrapolations of Drell-Yan to the LHC. Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 2 “Leading Jet” vs Z-Boson Studying the Studying the “ “ Underlying Event Underlying Event ” ” at CDF at CDF Proton AntiProton PT(hard) Outgoing Parton Outgoing Parton Underlying Event Underlying Event Initial-State Radiation Final-State Radiation Rick Field University of Florida Outline of Talk CDF Run 2 Proton AntiProton Drell-Yan Production Anti - Lepton Lepton Underlying Even t Un derlying Event ¨ The “Towards”, “Away”, and “Transverse” regions of η-φ space. ¨ Four Jet Topologies. ¨ The “transMAX” and “transMIN” regions. ¨ The observables: First look at average quantities. Then do distributions. ¨ Look at <p T > versus Nchg in “min-bias” and Drell-Yan. ¨ The “underlying event” in Drell-Yan production. “Leading Jet” ¨ Show some extrapolations of Drell-Yan to the LHC. The goal is to produce data (corrected to the particle level) that can be used by the theorists to tune and improve the QCD Monte-Carlo models that are used to simulate hadron-hadron collisions. Rick Field Craig Group Deepak Kar Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 3 QCD Monte QCD Monte - - Carlo Models: Carlo Models: High Transverse Momentum Jets High Transverse Momentum Jets ¨ Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and final- state gluon radiation (in the leading log approximation or modified leading log approximation). Hard Scattering PT(hard) Outgoing Parton Outgoing Parton Initial-State Radiation Final-State Radiation Hard Scattering PT(hard) Outgoing Parton Outgoing Parton Initial-State Radiation Final-State Radiation Proton AntiProton Underlying Event Underlying Event Proton AntiProton Underlying Event Underlying Event “Hard Scattering” Component “Underlying Event” ¨ 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 and final-state radiation. Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 4 QCD Monte QCD Monte - - Carlo Models: Carlo Models: High Transverse Momentum Jets High Transverse Momentum Jets ¨ Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and final- state gluon radiation (in the leading log approximation or modified leading log approximation). Hard Scattering PT(hard) Outgoing Parton Outgoing Parton Initial-State Radiation Final-State Radiation Hard Scattering PT(hard) Outgoing Parton Outgoing Parton Initial-State Radiation Final-State Radiation Proton AntiProton Underlying Event Underlying Event Proton AntiProton Underlying Event Underlying Event “Hard Scattering” Component “Jet” “Jet” “Underlying Event” ¨ 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 and final-state radiation. “Jet” The “underlying event” is an unavoidable background to most collider observables and having good understand of it leads to more precise collider measurements! Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 5 QCD Monte QCD Monte - - Carlo Models: Carlo Models: Lepton Lepton - - Pair Production Pair Production ¨ 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). Proton AntiProton Underlying Event Underlying Event Proton AntiProton Underlying Event Underlying Event “Hard Scattering” Component Lepton-Pair Production Lepton Anti-Lepton Initial-State Radiation Lepton-Pair Production Lepton Anti-Lepton Initial-State Radiation “Underlying Event” ¨ 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 and final-state radiation. “Jet” Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 6 -1 +1 φ 2 π 0 η Leading Jet Toward Region Transverse Region Transverse Region Away Region Away Region Jet #1 Direction Δφ “Transverse” “Transverse” “Toward” “Away” “Toward-Side” Jet “Awa y -Side” Jet “ “ Towards Towards ” ” , , “ “ Away Away ” ” , , “ “ Transverse Transverse ” ” ¨Look at correlations in the azimuthal angle Δφ relative to the leading charged particle jet (|η| < 1) or the leading calorimeter jet (|η| < 2). ¨Define |Δφ| < 60 o as “Toward”, 60 o < |Δφ| < 120 o as “Transverse ”, and |Δφ| > 120 o as “Away”. Each of the three regions have area ΔηΔφ = 2×120 o = 4π/3. Jet #1 Direction Δ φ “Toward” “Transverse” “Transverse” “Away” Δφ Correlations relative to the leading jet Charged particles p T > 0.5 GeV/c |η| < 1 Calorimeter towers E T > 0.1 GeV |η| < 1 “Transverse” region is very sensitive to the “underlying event”! Look at the charged particle density, the charged PTsum density and the ETsum density in all 3 regions! Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 7 -1 +1 φ 2 π 0 η Leading Jet Toward Region Transverse Region Transverse Region Away Region Away Region Jet #1 Direction Δφ “Transverse” “Transverse” “Toward” “Away” “Toward-Side” Jet “Awa y -Side” Jet “ “ Towards Towards ” ” , , “ “ Away Away ” ” , , “ “ Transverse Transverse ” ” ¨Look at correlations in the azimuthal angle Δφ relative to the leading charged particle jet (|η| < 1) or the leading calorimeter jet (|η| < 2). ¨Define |Δφ| < 60 o as “Toward”, 60 o < |Δφ| < 120 o as “Transverse ”, and |Δφ| > 120 o as “Away”. Each of the three regions have area ΔηΔφ = 2×120 o = 4π/3. Jet #1 Direction Δ φ “Toward” “Transverse” “Transverse” “Away” Δφ Correlations relative to the leading jet Charged particles p T > 0.5 GeV/c |η| < 1 Calorimeter towers E T > 0.1 GeV |η| < 1 “Transverse” region is very sensitive to the “underlying event”! Look at the charged particle density, the charged PTsum density and the ETsum density in all 3 regions! Z-Boson Direction Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 8 Event Topologies Event Topologies ¨“Leading Jet” events correspond to the leading calorimeter jet (MidPoint R = 0.7) in the region |η| < 2 with no other conditions. Jet #1 Direction Δ φ “Toward” “Transverse” “Transverse” “Away” “Leading Jet” ¨“Leading ChgJet” events correspond to the leading charged particle jet (R = 0.7) in the region |η| < 1 with no other conditions. ChgJet #1 Direction Δ φ “Toward” “Transverse” “Transverse” “Away” Jet #1 Direction Δφ “Toward” “Transverse” “Transverse” “Away” Jet #2 Direction “Charged Jet” “Inc2J Back-to-Back” “Exc2J Back-to-Back” ¨“Inclusive 2-Jet Back-to-Back” events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back- to-back” (Δφ 12 > 150 o ) with almost equal transverse energies (P T (jet#2)/P T (jet#1) > 0.8) with no other conditions . ¨“Exclusive 2-Jet Back-to-Back” events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back- to-back” (Δφ 12 > 150 o ) with almost equal transverse energies (P T (jet#2)/P T (jet#1) > 0.8) and P T (jet#3) < 15 GeV/c. subset subset Z-Boson Direction Δ φ “Toward” “Transverse” “Transverse” “Away” Z-Boson ¨“Z-Boson” events are Drell-Yan events with 70 < M(lepton-pair) < 110 GeV with no other conditions. Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 9 “ “ transMAX transMAX ” ” & & “ “ transMIN transMIN ” ” ¨Define the MAX and MIN “transverse” regions (“transMAX” and “transMIN”) on an event-by-event basis with MAX (MIN) having the largest (smallest) density. Each of the two “transverse” regions have an area in η-φ space of 4π/6. ¨The “transMIN” region is very sensitive to the “beam-beam remnant” and the soft multiple parton interaction components of the “underlying event”. Jet #1 Direction Δφ “Toward” “TransMAX” “TransMIN” “Away” Jet #1 Direction Δ φ “TransMAX” “TransMIN” “Toward” “Away” “Toward-Side” Jet “Away-Side” Jet Jet #3 ¨The difference, “transDIF” (“transMAX” minus “transMIN”), is very sensitive to the “hard scattering” component of the “underlying event” (i.e. hard initial and final-state radiation). Area = 4π/6 “transMIN” very sensitive to the “beam-beam remnants”! ¨The overall “transverse” density is the average of the “transMAX” and “transMIN” densities. Fourth HERA-LHC Workshop May 26-30, 2008 Rick Field – Florida/CDF/CMS Page 10 Jet #1 Direction Δφ “Toward” “Transverse” “Transverse” “Away” Jet #1 Direction Δφ “Toward” “Transverse” “Transverse” “Away” Jet #2 Direction “Back-to-Back” Scalar p T sum of “good” charged tracks (p T > 0.5 GeV/c, |η| < 1) divided by the scalar E T sum of calorimeter towers (E T > 0.1 GeV, |η| < 1) Scalar p T sum of charged particles (p T > 0.5 GeV/c, |η| < 1) divided by the scalar E T sum of all particles (all p T , |η| < 1) PTsum/ETsum Scalar E T sum of all calorimeter towers per unit η-φ (E T > 0.1 GeV, |η| < 1) Scalar E T sum of all particles per unit η-φ (all p T , |η| < 1) dETsum/dηdφ Maximum p T “good” charged tracks (p T > 0.5 GeV/c, |η| < 1) Require Nchg ≥ 1 Maximum p T charged particle (p T > 0.5 GeV/c, |η| < 1) Require Nchg ≥ 1 PTmax Average p T of “good” charged tracks (p T > 0.5 GeV/c, |η| < 1) Average p T of charged particles (p T > 0.5 GeV/c, |η| < 1) <p T > Scalar p T sum of “good” charged tracks per unit η-φ (p T > 0.5 GeV/c, |η| < 1) Scalar p T sum of charged particles per unit η-φ (p T > 0.5 GeV/c, |η| < 1) dPTsum/dηdφ Number of “good” charged tracks per unit η-φ (p T > 0.5 GeV/c, |η| < 1) Number of charged particles per unit η-φ (p T > 0.5 GeV/c, |η| < 1) dNchg/dηdφ Detector LevelParticle LevelObservable “Leading Jet” “ “ Leading Jet Leading Jet ” ” Observables at the Observables at the Particle and Detector Level Particle and Detector Level Also include the leading jet mass (new)! 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The data are corrected to the particle level ( with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle. May 26-30, 2008 Rick Field – Florida /CDF/ CMS Page 2 “Leading Jet” vs Z-Boson Studying the Studying the “ “ Underlying Event Underlying Event ” ” at CDF at CDF Proton AntiProton PT(hard) Outgoing. Outgoing Parton Initial-State Radiation Final-State Radiation Hard Scattering PT(hard) Outgoing Parton Outgoing Parton Initial-State Radiation Final-State Radiation Proton AntiProton