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New LHC Tunes: What We've Learned

This talk discusses the examination of the Tune Z1 and its fitting to LHC UE and MB data, as well as the improvement in agreement with increased pT. It also highlights the discrepancy in diffraction modeling and the need for tuning Monte-Carlo to fit the data. The importance of not tuning away new physics is emphasized.

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New LHC Tunes: What We've Learned

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  1. MPI@LHC 2010 New LHC Tunes: What we have learned Rick Field University of Florida Outline of Talk • The CDF Tevatron tunes do not produce enough soft particles. Glasgow, Scotland November 2010 • PYTHIA 6.4 Tune Z1: New CMS 6.4 MB tune (pT-ordered parton showers and new MPI). • Examine how well the Tune Z1 fits the LHC UE data (CMS, ATLAS, ALICE). • Examine how well Tune Z1 fits the LHC MB data (CMS,ATLAS, ALICE). Rick Field – Florida/CDF/CMS

  2. 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

  3. 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

  4. CMS dN/dh CMS Tune DW Soft particles! All pT • 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

  5. 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 • 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

  6. 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! Be careful not to tune away new physics! CMS Tune DW Soft particles! All pT • 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

  7. 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

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

  9. 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

  10. 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

  11. 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

  12. PYTHIA Tune Z1 ALICE ALICE Tune Z1 Tune Z1 • ALICE 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| < 0.8. The data are corrected and compared with PYTHIA Tune Z1 at the generator level. • ALICE 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| < 0.8. 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

  13. PYTHIA Tune Z1 ALICE ATLAS Tune Z1 Tune Z1 • ALICE 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| < 0.8. 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 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 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

  14. 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

  15. 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

  16. 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

  17. PYTHIA Tune Z1 ATLAS ATLAS Tune Z1 Tune Z1 Factor of 2 increase! • ATLAS preliminary data at 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. Also shows the prediction of Tune Z1 for the “transverse” charged particle density with pT > 0.1 GeV/c and |h| < 2.5. • ATLAS preliminary data at 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 generator level. Also shows the prediction of Tune Z1 for the “transverse” charged particle density with pT > 0.1 GeV/c and |h| < 2.5. Rick Field – Florida/CDF/CMS

  18. “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

  19. “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

  20. “Transverse” Multiplicity Distribution Same center-of-mass energy at two different hard scales! CMS CMS Tune Z1 Difficult to produce enough events with large “transverse” multiplicity at low hard scale! • 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 with PT(chgjet#1) > 3 GeV/c and PT(chgjet#1) > 20 GeV/c compared with PYTHIA Tune Z1 at the detector level (i.e. Theory + SIM). • 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 with PT(chgjet#1) > 3 GeV/c and PT(chgjet#1) > 20 GeV/c compared with PYTHIA Tune DW and Tune D6T at the detector level (i.e. Theory + SIM). Rick Field – Florida/CDF/CMS

  21. “Transverse” PTsum Distribution Same center-of-mass energy at two different hard scales! CMS CMS Tune Z1 • CMS uncorrected data at 7 TeV on the charged 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 and PT(chgjet#1) > 20 GeV/c compared with PYTHIA Tune Z1 at the detector level (i.e. Theory + SIM). • CMS uncorrected data at 7 TeV on the charged 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 and PT(chgjet#1) > 20 GeV/c compared with PYTHIA Tune DW and Tune D6T 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

  22. CMS dN/dh Tune Z1 CMS CMS • Generator level dN/dh (all pT). Shows the NSD = HC + DD and the HC = ND contributions for Tune Z1. Also shows the CMS NSD data. • Generator level dN/dh (all pT). Shows the NSD = HC + DD prediction for Tune Z1 and Tune X2. Also shows the CMS NSD data. Okay not perfect, but remember we do not know if the DD is correct! Rick Field – Florida/CDF/CMS

  23. PYTHIA Tune Z1 Tune Z1 • 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. Okay not perfect, but remember we do not know if the SD & DD are correct! Rick Field – Florida/CDF/CMS

  24. NSD Multiplicity Distribution Difficult to produce enough events with large multiplicity! CMS Tune Z1 • Generator level charged multiplicity distribution (all pT, |h| < 2) at 900 GeV and 7 TeV. Shows the NSD = HC + DD prediction for Tune Z1. Also shows the CMS NSD data. Okay not perfect! But not that bad! Rick Field – Florida/CDF/CMS

  25. NSD: <pT> versus Nchg CMS CMS Overall average pT Overall average pT • Shows the 900 GeV and 7 TeV CMS NSD corrected data on <pT> versus Nchg (all pT, |h| < 2.4) compared with Tune Z1. Okay not perfect! But not that bad! Rick Field – Florida/CDF/CMS

  26. NSD: <pT> versus Nchg <pT> increases by 20% • Note that for a given multiplicity <pT> increase only very slightly with in going from 900 GeV to 7 TeV (2%-4%). However, the average pT increases by ~20% due mainly from the broadening of the multiplicity distribution! Rick Field – Florida/CDF/CMS

  27. Energy Dependence Overall average pT • Shows the energy dependence of the CMS NSD corrected data on <pT> versus Nchg (all pT, |h| < 2.4) compared with Tune X2. Also shows the energy dependence of the overall <pT> compared with Tune X2. • Shows the energy dependence of the CMS NSD corrected data on <pT> versus Nchg (all pT, |h| < 2.4) compared with Tune P0, Tune PQ20, and Tune P329. It will be interesting to see if any tune can get this right! Rick Field – Florida/CDF/CMS

  28. Energy Dependence Amazing! ATLAS AMBT1 probably does well here also! • Shows the energy dependence of the CMS NSD corrected data on <pT> versus Nchg (all pT, |h| < 2.4) compared with Tune Z1. Also shows the energy dependence of the overall <pT> compared with Tune Z1. First Tune (except PhoJet) to come close here! Rick Field – Florida/CDF/CMS

  29. MB & UE “Min-Bias” CMS CMS Tune Z1 “Underlying Event” Tune Z1 Difficult to produce enough events with large multiplicity! • 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). Difficult to produce enough events with large “transverse” multiplicity at low hard scale! • Generator level charged multiplicity distribution (all pT, |h| < 2) at 900 GeV and 7 TeV. Shows the NSD = HC + DD prediction for Tune Z1. Also shows the CMS NSD data. Rick Field – Florida/CDF/CMS

  30. MB & UE CMS Tune Z1 • 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 with PT(chgjet#1) > 20 GeV/c compared with PYTHIA Tune Z1 at the detector level (i.e. Theory + SIM). Also shows the CMS corrected NSD multiplicity distribution (all pT, |h| < 2) compared with Tune Z1 at the generator. Amazing what we are asking the Monte-Carlo models to fit! Rick Field – Florida/CDF/CMS

  31. Strange Particle Production • A lot more strange mesons at large pT than predicted by the Monte-Carlo Models! • K/p ratio fairly independent of the center-of-mass energy. Factor of 2! ALICE preliminary stat. error only Phojet Pythia ATLAS-CSC Pythia D6T Pythia Perugia-0 Rick Field – Florida/CDF/CMS

  32. The LHC in 2011 • Beam back around 21st February. • Beam back around on February 21st! • 2 weeks re-commissioning with beam (at least). This is fun! • 4 day technical stop every 6 weeks. • 4 weeks ion run. • End of run – December 12th. • Approximately 200 days proton physics! • Maybe 8 TeV (4 TeV/beam). Rick Field – Florida/CDF/CMS

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