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Early LHC Measurements

Early LHC Measurements. MC Tunes: What have we learned?. Rick Field University of Florida. PARP(82). PARP(90). Outline of Talk. The new ATLAS & CMS “underlying event” results. Color. Diffraction. Connections. UE Summary. LHC “min-bias” data at 7 TeV. “Min-bias” Summary. UE&MB@CMS.

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Early LHC Measurements

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  1. Early LHC Measurements MC Tunes: What have we learned? Rick Field University of Florida PARP(82) PARP(90) Outline of Talk • The new ATLAS & CMS “underlying event” results. Color Diffraction Connections • UE Summary. • LHC “min-bias” data at 7 TeV. • “Min-bias” Summary. UE&MB@CMS Rick Field – Florida/CDF/CMS

  2. ATLAS & CMS UE Analyses • 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. • 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. UE&MB@CMS Rick Field – Florida/CDF/CMS

  3. Please note that I have read the ATLAS and CMS data points off these papers with a ruler so that I can plot the data and make comparisons! Please refer to these papers (not my plots) for the true data points! ATLAS & CMS UE Analyses • 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. • 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. None of my plots are the original figures from the papers! UE&MB@CMS Rick Field – Florida/CDF/CMS

  4. “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). Rick Field MB&UE@CMS Workshop CERN, November 6, 2009 Rick Field – Florida/CDF/CMS

  5. “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

  6. “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

  7. PYTHIA Tune CW • 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 CW after detector simulation. • 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 CW after detector simulation. Tune DW → Tune CW PARP(82) = 1.9 → 1.8 PARP(90) = 0.25 → 0.30 PARP(85) = 1.0 → 0.9 PARP(86) = 1.0 → 0.95 Rick Field – Florida/CDF/CMS

  8. “Transverse” Charge Density Rick Field MB&UE@CMS Workshop CERN, November 6, 2009 factor of 2! 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

  9. “Transverse” Charge Density factor of 2! 900 GeV → 7 TeV (UE increase ~ factor of 2) LHC 900 GeV LHC 7 TeV ~0.4 → ~0.8 • 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. Rick Field – Florida/CDF/CMS

  10. “Transverse” Charge Density PARP(90) = 0.16 PARP(90) = 0.25 PARP(90) = 0.30 900 GeV → 7 TeV (UE increase ~ factor of 2) LHC 900 GeV LHC 7 TeV ~0.4 → ~0.8 • 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 CW, DW, and ATLAS MC08. Rick Field – Florida/CDF/CMS

  11. 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. • 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 generrator level. Rick Field – Florida/CDF/CMS

  12. Tuning the Color Connections • Shows the charged particle and PTsum density in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2.5) at 7 TeVas defined by the leading charged particle, PTmax, for pyX18GG8, pyX18GG1, and pyX18QQat the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  13. Tuning the Color Connections GG8 has larger <pT>! • Shows the charged particle average pT in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2.5) at 7 TeVas defined by the leading charged particle, PTmax, for pyX18GG8, pyX18GG1, and pyX18QQat the particle level (i.e. generator level). Tune A has 90% GG8 and Tune DW and D6T have 100% GG8 in order to fit the <pT> and PTsum/Nchg at the Tevatron! Rick Field – Florida/CDF/CMS

  14. Tuning the Color Connections GG8 has larger <pT>! • Shows the charged particle average pT in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2.5) at 7 TeVas defined by the leading charged particle, PTmax, for pyX18GG8, pyX18GG1, and pyX18QQat the particle level (i.e. generator level). Tune A has 90% GG8 and Tune DW and D6T have 100% GG8 in order to fit the <pT> and PTsum/Nchg at the Tevatron! Rick Field – Florida/CDF/CMS

  15. Tuning the Color Connections GG8 has larger PTsum/Nchg! • Shows the charged particle ratio PTsum/Nchg in the “transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2.5) at 7 TeVas defined by the leading charged particle, PTmax, for pyX18GG8, pyX18GG1, and pyX18QQat the particle level (i.e. generator level). Rick Field – Florida/CDF/CMS

  16. PYTHIA Tune X1 • 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 X1 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 X1 at the generrator level. Tune X1 → Tune CW PARP(82) = 1.9 → 1.8 PARP(85) = 1.0 → 0.8 PARP(86) = 1.0 → 0.9 Rick Field – Florida/CDF/CMS

  17. PYTHIA Tune X1 • 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 X1 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 X1 at the generator level. Tune X1 → Tune CW PARP(82) = 1.9 → 1.8 PARP(85) = 1.0 → 0.8 PARP(86) = 1.0 → 0.9 Rick Field – Florida/CDF/CMS

  18. PYTHIA Tune X1 • 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 X1 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 X1 at the generator level. Tune X1 → Tune CW PARP(82) = 1.9 → 1.8 PARP(85) = 1.0 → 0.8 PARP(86) = 1.0 → 0.9 Rick Field – Florida/CDF/CMS

  19. CDF Run 2 Min-Bias “Associated”Charged Particle Density PY Tune A PTmax > 2.0 GeV/c Transverse Region Transverse Region PTmax > 0.5 GeV/c • Shows the data on the Df dependence of the “associated” charged particle density, dNchg/dhdf, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” eventswith PTmax > 0.5 GeV/c and PTmax > 2.0 GeV/c compared with PYTHIA Tune A (after CDFSIM). • PYTHIA Tune A predicts a larger correlation than is seen in the “min-bias” data (i.e.Tune A “min-bias” is a bit too “jetty”). Rick Field – Florida/CDF/CMS

  20. The problem in fitting the “toward” associated particle density seen 10 years ago at CDF also appears at 900 GeV and 7 TeV in the ATLAS & CMS data! CDF Run 2 Min-Bias “Associated”Charged Particle Density PY Tune A PTmax > 2.0 GeV/c Transverse Region Transverse Region PTmax > 0.5 GeV/c • Shows the data on the Df dependence of the “associated” charged particle density, dNchg/dhdf, for charged particles (pT > 0.5 GeV/c, |h| < 1, not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” eventswith PTmax > 0.5 GeV/c and PTmax > 2.0 GeV/c compared with PYTHIA Tune A (after CDFSIM). • PYTHIA Tune A predicts a larger correlation than is seen in the “min-bias” data (i.e.Tune A “min-bias” is a bit too “jetty”). Rick Field – Florida/CDF/CMS

  21. UE Summary • The “underlying event” at 7 TeV and 900 GeV is almost what we expected! I expect that a PYTHIA 6 tune just slightly different than Tune DW will fit the UE data perfectly including the energy dependence (Tune X1 is not bad!). I also expect to see good PYTHIA 8 tune soon! PARP(82) PARP(90) • “Min-Bias” is a whole different story! Much more complicated due to diffraction! Color Diffraction • I will quickly show you some of my attempts (all failures) to fit the LHC “min-bias” data. Connections Rick Field – Florida/CDF/CMS

  22. <PT> versus Nchg • Shows how changing the color connections affects the <pT> versus Nchg . Here the data and theory are non-diffractive (ND). Here you can understand why Tune DW rises faster than the data and why the ATLAS tunes does so poorly. • CDF ND data on the <pT> versus Nchg compared with Tune A(ND), Tune DW(ND) and Tune ATLAS MC08(ND). This is why no one likes the ATLAS MC08 Tune! The CDF “min-bias” data are telling us that the correct tune must be largely GG8! Okay Tune A and DW have a little to much GG8! Rick Field – Florida/CDF/CMS

  23. <PT> versus Nchg Tune X1! • Shows how changing the color connections affects the <pT> versus Nchg . Here the data and theory are non-diffractive (ND). Here you can understand why Tune DW rises faster than the data and why the ATLAS tunes does so poorly. • CDF ND data on the <pT> versus Nchg compared with Tune A(ND), Tune DW(ND) and Tune ATLAS MC08(ND). This is why no one likes the ATLAS MC08 Tune! The CDF “min-bias” data are telling us that the correct tune must be largely GG8! Okay Tune A and DW have a little to much GG8! Rick Field – Florida/CDF/CMS

  24. PYTHIA Tune X2 • For Tune X2 I will attempt to produce enough charged particles (all pT) at 7 TeV (i.e. fit the CMS NSD dN/dh distribution). It is important to have a tune that gets the average multiplicity right! I will only look at 7 TeV “min-bias” data. Tune X2 does fit the “underlying event” data! • Tune X2 uses the PYTHIA HC, SD, DD fractions for INEL (above left) and HC, DD fractions for NSD (above right). PYTHIA is thought to predict to much SD and DD. Tune X3 (not ready yet) will use the ALICE DD and SD fractions (see above). For now I will try and do the best possible using the PYTHIA SD and DD fractions. Rick Field – Florida/CDF/CMS

  25. Color Connections CMS • Shows how changing the color connections affects the average number of charged particles. Also shows the SD and ND contributions. CMS sees about ~24 charged particles (all pT, |h| < 2). Rick Field – Florida/CDF/CMS

  26. Color Connections pyATLAS is equal mixtures of all three! DW, DWT, and D6T are 100% GG8! • Generator level dN/dh (all pT). Shows the HC contribution for the three color connections GG8, GG1, and QQbar. Also shows the CMS NSD data. Rick Field – Florida/CDF/CMS

  27. PYTHIA Tune X2 • Generator level dN/dh (all pT). Shows the NSD = HC + DD, HC = ND, and DD contributions for Tune X2. Also shows the CMS NSD data. Rick Field – Florida/CDF/CMS

  28. PYTHIA Tune X2 SD = 9.4%, DD = 6.8%! • Shows the CMS NSD data for dN/dh (all pT) and the ATLAS INEL data for dN/dh (pT > 0.5 GeV/c, Nchg ≥ 1) compared with Tune X2 (generator level). Rick Field – Florida/CDF/CMS

  29. Color Connections CMS Tune X2 gives the right average number of charged particles but <pT> = 0.501 is a long way off on the the observed average pT (i.e. too small)! • Shows how changing the color connections affects the average transverse momentum of charged particles. Also shows the SD and ND contributions. CMS sees <pT> ~ 0.545 GeV/c (all pT, |h| < 2). Rick Field – Florida/CDF/CMS

  30. PYTHIA Tune X2 • Shows the CMS NSD data for <pT> versus Nchg (all pT) and the ATLAS INEL data for <pT> versus Nchg (pT > 0.5 GeV/c, Nchg ≥ 1) compared with Tune X2 (generator level). Rick Field – Florida/CDF/CMS

  31. Color Connections Gives the right <pT>! • Shows the ATLAS INEL data for <pT> versus Nchg (pT > 0.5 GeV/c, Nchg ≥ 1) compared with Tune X18GG8, X18GG1, and X18QQ (left) and PYTHIA Tune X1844 (INEL, right). Rick Field – Florida/CDF/CMS

  32. Color Connections • Shows the ATLAS INEL data for <pT> versus Nchg (pT > 0.5 GeV/c, Nchg ≥ 1) compared with Tune X18GG8, X18GG1, and X18QQ (left) and PYTHIA Tune X1844 (INEL, right). Rick Field – Florida/CDF/CMS

  33. Min-Bias Summary • We are learning a lot about how nature works! • We are a long way from having a model that will fit all the features of the LHC min-bias data! • I think the problem is that we do not understand diffraction well enough yet! PARP(82) PARP(90) Color Diffraction Connections Rick Field – Florida/CDF/CMS

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