1 / 70

Early LHC Physics

Early LHC Physics. QCD at the LHC: Findings & Surprises. Rick Field University of Florida. Outline of Talk. How well did we do at predicting the behavior of the “underlying event” at 900 GeV and 7 TeV? A careful look. University of Florida November 2010.

reynold
Download Presentation

Early LHC Physics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Early LHC Physics QCD at the LHC: Findings & Surprises Rick Field University of Florida Outline of Talk • How well did we do at predicting the behavior of the “underlying event” at 900 GeV and 7 TeV? A careful look. University of Florida November 2010 • How well did we do at predicting the behavior of “min-bias” collisions at 900 GeV and 7 TeV? A careful look. • PYTHIA 6.4 Tune Z1: New CMS 6.4 tune (pT-ordered parton showers and new MPI). • New Physics in Min-Bias?? Observation of long-range same-side correlations at 7 TeV. UE&MB@CMS Rick Field – Florida/CDF/CMS

  2. “Hard Scattering” Component QCD Monte-Carlo Models: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). “Underlying Event” • The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or semi-soft multiple parton interactions (MPI). The “underlying event” is an unavoidable background to most collider observables and having good understand of it leads to more precise collider measurements! • Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event” observables receive contributions from initial and final-state radiation. Rick Field – Florida/CDF/CMS

  3. Proton Proton Proton Proton MPI, Pile-Up, and Overlap MPI: Multiple Parton Interactions • MPI: Additional 2-to-2 parton-parton scatterings within a single hadron-hadron collision. Pile-Up Interaction Region Dz • Pile-Up: More than one hadron-hadron collision in the beam crossing. Overlap • Overlap: An experimental timing issue where a hadron-hadron collision from the next beam crossing gets included in the hadron-hadron collision from the current beam crossing because the next crossing happened before the event could be read out. Rick Field – Florida/CDF/CMS

  4. Traditional Approach CDF Run 1 Analysis • Look at charged particle correlations in the azimuthal angle Df relative to a leading object (i.e. CaloJet#1, ChgJet#1, PTmax, Z-boson). For CDF PTmin = 0.5 GeV/c hcut = 1. Charged Particle Df Correlations PT > PTmin |h| < hcut Leading Calorimeter Jet or Leading Charged Particle Jet or Leading Charged Particle or Z-Boson “Transverse” region very sensitive to the “underlying event”! • Define |Df| < 60o as “Toward”, 60o < |Df| < 120o as “Transverse”, and |Df| > 120o as “Away”. • All three regions have the same area in h-f space, Dh×Df = 2hcut×120o = 2hcut×2p/3. Construct densities by dividing by the area in h-f space. Rick Field – Florida/CDF/CMS

  5. CMS UE Analyses Traditional Approach • Uncorrected data on the “transverse” region as defined by the leading track, PTmax, and the leading charged particle jet, PT(chgjet#1) at 900 GeV (pT > 0.5 GeV/c, |h| < 2.0) compared with several QCD Monte-Carlo models after detector simulation. Now published in EPJC! • Uncorrected data on the “transverse” region as defined by the leading charged particle jet, PT(chgjet#1) at 7 TeV and 900 GeV (pT > 0.5 GeV/c, |h| < 2.0) compared with several QCD Monte-Carlo models after detector simulation. UE&MB@CMS Rick Field – Florida/CDF/CMS

  6. CMS UE Analyses New Approach Method proposed by Gavin Salam et. al. Rick Field – Florida/CDF/CMS

  7. ATLAS UE Analysis • Corrected data on the “towards”, “away”, and “transverse” regions as defined by the leading track, PTmax, at 7 TeV and 900 GeV (pT > 0.5 GeV/c, |h| < 2.5) compared with several QCD Monte-Carlo models at the generator level. Traditional Approach Rick Field – Florida/CDF/CMS

  8. “Transverse” Charged Particle Density • Fake data (from MC) at 900 GeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle (PTmax) and the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The fake data (from PYTHIA Tune DW) are generated at the particle level (i.e. generator level) assuming 0.5 M min-bias events at 900 GeV (361,595 events in the plot). Leading Charged Particle Jet, chgjet#1. Prediction! Leading Charged Particle, PTmax. Rick Field MB&UE@CMS Workshop CERN, November 6, 2009 Rick Field – Florida/CDF/CMS

  9. “Transverse” Charged Particle Density • Fake data (from MC) at 900 GeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle (PTmax) and the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The fake data (from PYTHIA Tune DW) are generated at the particle level (i.e. generator level) assuming 0.5 M min-bias events at 900 GeV (361,595 events in the plot). • CMS preliminary data at 900 GeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle (PTmax) and the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation (216,215 events in the plot). Rick Field – Florida/CDF/CMS

  10. “Transverse” Charged PTsum Density • Fake data (from MC) at 900 GeV on the “transverse” charged PTsum density, dPT/dhdf, as defined by the leading charged particle (PTmax) and the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The fake data (from PYTHIA Tune DW) are generated at the particle level (i.e. generator level) assuming 0.5 M min-bias events at 900 GeV (361,595 events in the plot). • CMS preliminary data at 900 GeV on the “transverse” charged PTsum density, dPT/dhdf, as defined by the leading charged particle (PTmax) and the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation (216,215 events in the plot). Rick Field – Florida/CDF/CMS

  11. PYTHIA Tune DW • CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. Rick Field – Florida/CDF/CMS

  12. PYTHIA Tune DW • ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |h| < 2.5. The data are corrected and compared with PYTHIA Tune DW at the generator level. Rick Field – Florida/CDF/CMS

  13. PYTHIA Tune DW CMS ATLAS • ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |h| < 2.5. The data are corrected and compared with PYTHIA Tune DW at the generator level. • CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. Rick Field – Florida/CDF/CMS

  14. PYTHIA Tune DW CMS ATLAS • ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dhdf, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |h| < 2.5. The data are corrected and compared with PYTHIA Tune DW at the generator level. • CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. Rick Field – Florida/CDF/CMS

  15. “Transverse” Charge Density Rick Field MB&UE@CMS Workshop CERN, November 6, 2009 factor of 2! Prediction! 900 GeV → 7 TeV (UE increase ~ factor of 2) LHC 900 GeV LHC 7 TeV ~0.4 → ~0.8 • Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2) at 900 GeV and 7 TeVas defined by PTmax from PYTHIATune DW andat the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  16. PYTHIA Tune DW Ratio CMS CMS • Ratio of CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. • CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. Rick Field – Florida/CDF/CMS

  17. PYTHIA Tune DW CMS ATLAS • Ratio of CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. • Ratio of the ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |h| < 2.5. The data are corrected and compared with PYTHIA Tune DW at the generator level. Rick Field – Florida/CDF/CMS

  18. PYTHIA Tune DW CMS ATLAS • Ratio of the ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dhdf, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |h| < 2.5. The data are corrected and compared with PYTHIA Tune DW at the generator level. • Ratio of the CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. Rick Field – Florida/CDF/CMS

  19. “Transverse” Multiplicity Distribution Same hard scale at two different center-of-mass energies! CMS • CMS uncorrected data at 900 GeV and 7 TeV on the charged particle multiplicity distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2) as defined by the leading charged particle jet, chgjet#1, with PT(chgjet#1) > 3 GeV/c compared with PYTHIA Tune DW at the detector level (i.e. Theory + SIM). Shows the growth of the “underlying event” as the center-of-mass energy increases. Rick Field – Florida/CDF/CMS

  20. “Transverse” Multiplicity Distribution Same center-of-mass energy at two different hard scales! CMS • CMS uncorrected data at 7 TeV on the charged particle multiplicity distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2) as defined by the leading charged particle jet, chgjet#1, with PT(chgjet#1) > 3 GeV/c and PT(chgjet#1) > 20 GeV/c compared with PYTHIA Tune DW at the detector level (i.e. Theory + SIM). Shows the growth of the “underlying event” as the hard scale increases. Rick Field – Florida/CDF/CMS

  21. PYTHIA Tune DW How well did we do at predicting the “underlying event” at 900 GeV and 7 TeV? Tune DW Tune DW • I am surprised that the Tunes did not do a better job of predicting the behavior of the “underlying event” at 900 GeV and 7 TeV! Tune DW Rick Field – Florida/CDF/CMS

  22. PYTHIA Tune DW How well did we do at predicting the “underlying event” at 900 GeV and 7 TeV? Tune DW Tune DW • I am surprised that the Tunes did as well as they did at predicting the behavior of the “underlying event” at 900 GeV and 7 TeV! Tune DW Rick Field – Florida/CDF/CMS

  23. PARP(82) PARP(90) Color Diffraction Connections UE Summary Warning! All the UE studies look at charged particles with pT > 0.5 GeV/c. We do not know if the models correctly describe the UE at lower pT values! • The “underlying event” at 7 TeV and 900 GeV is almost what we expected! With a little tuning we should be able to describe the data very well (see Tune Z1 later in this talk). • I am surprised that the Tunes did as well as they did at predicting the behavior of the “underlying event” at 900 GeV and 7 TeV! Remember this is “soft” QCD! • “Min-Bias” is a whole different story! Much more complicated due to very soft particles and diffraction! Rick Field – Florida/CDF/CMS

  24. Rick Field University of ChicagoJuly 11, 2006 “Back-to-Back” “Leading Jet” Neither PY Tune A or HERWIG fits the ETsum density in the “transferse” region! HERWIG does slightly better than Tune A! • Shows the data on the tower ETsum density, dETsum/dhdf, in the “transMAX” and “transMIN” region (ET > 100 MeV, |h| < 1) versus PT(jet#1) for “Leading Jet” and “Back-to-Back” events. • Compares the (corrected) data with PYTHIA Tune A (with MPI) and HERWIG (without MPI) at the particle level (all particles, |h| < 1). Rick Field – Florida/CDF/CMS

  25. Rick Field University of ChicagoJuly 11, 2006 Possible Scenario?? • PYTHIA Tune A fits the charged particle PTsum density for pT > 0.5 GeV/c, but it does not produce enough ETsum for towers with ET > 0.1 GeV. • It is possible that there is a sharp rise in the number of particles in the “underlying event” at low pT (i.e. pT < 0.5 GeV/c). • Perhaps there are two components, a vary “soft” beam-beam remnant component (Gaussian or exponential) and a “hard” multiple interaction component. Rick Field – Florida/CDF/CMS

  26. Proton-Proton Collisions stot = sEL + sSD+sDD+sHC stot = sEL + sIN ND “Inelastic Non-Diffractive Component” The “hard core” component contains both “hard” and “soft” collisions. Rick Field – Florida/CDF/CMS

  27. The Inelastic Non-Diffractive Cross-Section Occasionally one of the parton-parton collisions is hard (pT > ≈2 GeV/c) Majority of “min-bias” events! “Semi-hard” parton-parton collision (pT < ≈2 GeV/c) + + + + … Multiple-parton interactions (MPI)! Rick Field – Florida/CDF/CMS

  28. The “Underlying Event” Select inelastic non-diffractive events that contain a hard scattering 1/(pT)4→ 1/(pT2+pT02)2 Hard parton-parton collisions is hard (pT > ≈2 GeV/c) “Semi-hard” parton-parton collision (pT < ≈2 GeV/c) The “underlying-event” (UE)! + + + … Given that you have one hard scattering it is more probable to have MPI! Hence, the UE has more activity than “min-bias”. Multiple-parton interactions (MPI)! Rick Field – Florida/CDF/CMS

  29. Model of sND Allow leading hard scattering to go to zero pT with same cut-off as the MPI! “Semi-hard” parton-parton collision (pT < ≈2 GeV/c) 1/(pT)4→ 1/(pT2+pT02)2 Model of the inelastic non-diffractive cross section! + + + + … Multiple-parton interactions (MPI)! Rick Field – Florida/CDF/CMS

  30. UE Tunes Allow primary hard-scattering to go to pT = 0 with same cut-off! “Underlying Event” All of Rick’s tunes (except X2): A, AW, AWT,DW, DWT, D6, D6T, CW, X1, and Tune Z1, are UE tunes! Fit the “underlying event” in a hard scattering process. 1/(pT)4→ 1/(pT2+pT02)2 “Min-Bias” (ND) “Min-Bias” (add single & double diffraction) + + + Predict MB (ND)! + … Predict MB (IN)! Rick Field – Florida/CDF/CMS

  31. Charged Particle Multiplicity • Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |h| < 1) for “min-bias” collisions at CDF Run 2 (non-diffractive cross-section). Tune A! No MPI! • The data are compared with PYTHIA Tune A and Tune A without multiple parton interactions (pyAnoMPI). Rick Field – Florida/CDF/CMS

  32. PYTHIA Tune A Min-Bias“Soft” + ”Hard” New Ten decades! 12% of “Min-Bias” events have PT(hard) > 5 GeV/c! 1% of “Min-Bias” events have PT(hard) > 10 GeV/c! Lots of “hard” scattering in “Min-Bias” at the Tevatron! • Comparison of PYTHIA Tune A with the pT distribution of charged particles for “min-bias” collisions at CDF Run 1 (non-diffractive cross-section). pT = 50 GeV/c! • PYTHIA Tune A predicts that 12% of all “Min-Bias” events are a result of a hard 2-to-2 parton-parton scattering with PT(hard) > 5 GeV/c (1% with PT(hard) > 10 GeV/c)! Rick Field – Florida/CDF/CMS

  33. CDF: Charged pT Distribution • Published CDF data on the pT distribution of charged particles in Min-Bias collisions (ND) at 1.96 TeV compared with PYTHIA Tune A. Erratum November 18, 2010 Excess events at large pT! No excess at large pT! 50 GeV/c! CDF consistent with CMS and UA1! CDF inconsistent with CMS and UA1! Rick Field – Florida/CDF/CMS

  34. MB Tunes “Underlying Event” Most of Peter Skand’s tunes: S320 Perugia 0, S325 Perugia X, S326 Perugia 6 are MB tunes! Predict the “underlying event” in a hard scattering process! “Min-Bias” (ND) + + + Fit MB (ND). + … Rick Field – Florida/CDF/CMS

  35. MB+UE Tunes “Underlying Event” Most of Hendrik’s “Professor” tunes: ProQ20, P329 are MB+UE! Fit the “underlying event” in a hard scattering process! “Min-Bias” (ND) Simultaneous fit to both MB & UE + + + The ATLAS AMBT1 Tune is an MB+UE tune, but because they include in the fit the ATLAS UE data with PTmax > 10 GeV/c (big errors) the LHC UE data does not have much pull (hence mostly an MB tune!). Fit MB (ND). + … Rick Field – Florida/CDF/CMS

  36. LHC MB Predictions: 900 GeV Off by 11%! • Compares the 900 GeV ALICE data with PYTHIA Tune DW and Tune S320 Perugia 0. Tune DW uses the old Q2-ordered parton shower and the old MPI model. Tune S320 uses the new pT-ordered parton shower and the new MPI model. The numbers in parentheses are the average value of dN/dh for the region |h| < 0.6. Rick Field – Florida/CDF/CMS

  37. ATLAS INEL dN/dh • None of the tunes fit the ATLAS INEL dN/dh data with PT > 100 MeV! They all predict too few particles. Off by 20-50%! • The ATLAS Tune AMBT1 was designed to fit the inelastic data for Nchg ≥ 6 with pT > 0.5 GeV/c! Soft particles! Rick Field – Florida/CDF/CMS

  38. PYTHIA Tune DW If one increases the pT the agreement improves! Tune DW • ALICE inelastic data at 900 GeV on the dN/dh distribution for charged particles (pT > PTmin) for events with at least one charged particle with pT > PTmin and |h| < 0.8 for PTmin = 0.15 GeV/c, 0.5 GeV/c, and 1.0 GeV/c compared with PYTHIA Tune DW at the generator level. The same thing occurs at 7 TeV! ALICE, ATLAS, and CMS data coming soon. Rick Field – Florida/CDF/CMS

  39. PYTHIA Tune DW Diffraction contributes less at harder scales! Tune DW • ALICE inelastic data at 900 GeV on the dN/dh distribution for charged particles (pT > PTmin) for events with at least one charged particle with pT > PTmin and |h| < 0.8 for PTmin = 0.15 GeV/c, 0.5 GeV/c, and 1.0 GeV/c compared with PYTHIA Tune Z1 at the generator level (dashed = ND, solid = INEL). Cannot trust PYTHIA 6.2 modeling of diffraction! Rick Field – Florida/CDF/CMS

  40. CMS dN/dh Okay if the Monte-Carlo does not fit the data what do we do? We tune the Monte-Carlo to fit the data! CMS Tune DW Soft particles! All pT Be careful not to tune away new physics! • Generator level dN/dh (all pT). Shows the NSD = HC + DD and the HC = ND contributions for Tune DW. Also shows the CMS NSD data. Off by 50%! Rick Field – Florida/CDF/CMS

  41. PYTHIA Tune Z1 • All my previous tunes (A, DW, DWT, D6, D6T, CW, X1, and X2) were PYTHIA 6.4 tunes using the old Q2-ordered parton showers and the old MPI model (really 6.2 tunes)! PARP(90) PARP(82) Color • I believe that it is time to move to PYTHIA 6.4 (pT-ordered parton showers and new MPI model)! Connections Diffraction • Tune Z1: I started with the parameters of ATLAS Tune AMBT1, but I changed LO* to CTEQ5L and I varied PARP(82) and PARP(90) to get a very good fit of the CMS UE data at 900 GeV and 7 TeV. • The ATLAS Tune AMBT1 was designed to fit the inelastic data for Nchg ≥ 6 and to fit the PTmax UE data with PTmax > 10 GeV/c. Tune AMBT1 is primarily a min-bias tune, while Tune Z1 is a UE tune! UE&MB@CMS Rick Field – Florida/CDF/CMS

  42. PYTHIA Tune Z1 Parameters not shown are the PYTHIA 6.4 defaults! Rick Field – Florida/CDF/CMS

  43. PYTHIA Tune Z1 CMS CMS Tune Z1 • CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2.0. The data are uncorrected and compared with PYTHIA Tune DW and D6T after detector simulation (SIM). • CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2.0. The data are uncorrected and compared with PYTHIA Tune Z1 after detector simulation (SIM). Tune Z1 (CTEQ5L) PARP(82) = 1.932 PARP(90) = 0.275 PARP(77) = 1.016 PARP(78) = 0.538 Color reconnection suppression. Color reconnection strength. Tune Z1 is a PYTHIA 6.4 using pT-ordered parton showers and the new MPI model! Rick Field – Florida/CDF/CMS

  44. PYTHIA Tune Z1 CMS CMS Tune Z1 • CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2.0. The data are uncorrected and compared with PYTHIA Tune DW and D6T after detector simulation (SIM). • CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2.0. The data are uncorrected and compared with PYTHIA Tune Z1 after detector simulation (SIM). Tune Z1 (CTEQ5L) PARP(82) = 1.932 PARP(90) = 0.275 PARP(77) = 1.016 PARP(78) = 0.538 Color reconnection suppression. Color reconnection strength. Tune Z1 is a PYTHIA 6.4 using pT-ordered parton showers and the new MPI model! Rick Field – Florida/CDF/CMS

  45. PYTHIA Tune Z1 ATLAS ATLAS Tune Z1 Tune Z1 • ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dhdf, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |h| < 2.5. The data are corrected and compared with PYTHIA Tune Z1 at the generator level. • ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dhdf, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |h| < 2.5. The data are corrected and compared with PYTHIA Tune Z1 at the generrator level. Tune Z1 (CTEQ5L) PARP(82) = 1.932 PARP(90) = 0.275 PARP(77) = 1.016 PARP(78) = 0.538 Color reconnection suppression. Color reconnection strength. Tune Z1 is a PYTHIA 6.4 using pT-ordered parton showers and the new MPI model! Rick Field – Florida/CDF/CMS

  46. PYTHIA Tune Z1 Tune Z1 CMS CMS • Ratio of CMS preliminary data at 900 GeV and 7 TeV (7 TeV divided by 900 GeV) on the “transverse” charged particle density as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2.0. The data are uncorrected and compared with PYTHIA Tune DW, D6T, CW, and P0 after detector simulation (SIM). • Ratio of CMS preliminary data at 900 GeV and 7 TeV (7 TeV divided by 900 GeV) on the “transverse” charged particle density as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2.0. The data are uncorrected and compared with PYTHIA Tune Z1 after detector simulation (SIM). Rick Field – Florida/CDF/CMS

  47. PYTHIA Tune Z1 Tune Z1 CMS CMS • Ratio of CMS preliminary data at 900 GeV and 7 TeV (7 TeV divided by 900 GeV) on the “transverse” charged PTsum density as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2.0. The data are uncorrected and compared with PYTHIA Tune DW, D6T, CW, and P0 after detector simulation (SIM). • Ratio of CMS preliminary data at 900 GeV and 7 TeV (7 TeV divided by 900 GeV) on the “transverse” charged PTsum density as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and |h| < 2.0. The data are uncorrected and compared with PYTHIA Tune Z1 after detector simulation (SIM). Rick Field – Florida/CDF/CMS

  48. PYTHIA Tune Z1 Tune Z1 Tune Z1 ATLAS ATLAS • Ratio of the ATLAS preliminary data on the charged particle density in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2.5) at 900 GeV and 7 TeVas defined by PTmax compared with PYTHIA Tune Z1 at the generator level. • Ratio of the ATLAS preliminary data on the charged PTsum density in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2.5) at 900 GeV and 7 TeVas defined by PTmax compared with PYTHIA Tune Z1 at the generator level. Rick Field – Florida/CDF/CMS

  49. “Transverse” Multiplicity Distribution Same hard scale at two different center-of-mass energies! CMS CMS Tune Z1 Difficult to produce enough events with large “transverse” multiplicity at low hard scale! • CMS uncorrected data at 900 GeV and 7 TeV on the charged particle multiplicity distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2) as defined by the leading charged particle jet with PT(chgjet#1) > 3 GeV/c compared with PYTHIA Tune Z1 at the detector level (i.e. Theory + SIM). • CMS uncorrected data at 900 GeV and 7 TeV on the charged particle multiplicity distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2) as defined by the leading charged particle jet with PT(chgjet#1) > 3 GeV/c compared with PYTHIA Tune DW and Tune D6T at the detector level (i.e. Theory + SIM). Rick Field – Florida/CDF/CMS

  50. “Transverse” PTsum Distribution Same hard scale at two different center-of-mass energies! CMS CMS Tune Z1 • CMS uncorrected data at 900 GeV and 7 TeV on the charged scalar PTsum distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2) as defined by the leading charged particle jet with PT(chgjet#1) > 3 GeV/c compared with PYTHIA Tune DW,andTune D6T at the detector level (i.e. Theory + SIM). • CMS uncorrected data at 900 GeV and 7 TeV on the charged scalar PTsum distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2) as defined by the leading charged particle jet with PT(chgjet#1) > 3 GeV/c compared with PYTHIA Tune Z1,at the detector level (i.e. Theory + SIM). Difficult to produce enough events with large “transverse” PTsum at low hard scale! Rick Field – Florida/CDF/CMS

More Related