Early LHC Physics QCD at the LHC Findings

Early LHC Physics QCD at the LHC: Findings & Surprises Rick Field University of Florida Outline of Talk Æ How well did we do at predicting the behavior of the “underlying event” at 900 Ge. V and 7 Te. V? A careful look. University of Florida November 2010 Æ How well did we do at predicting the behavior of “min -bias” collisions at 900 Ge. V and 7 Te. V? A careful look. Æ PYTHIA 6. 4 Tune Z 1: New CMS 6. 4 tune (p. T -ordered parton showers and new MPI). Æ New Physics in Min-Bias? ? Observation of long-range same-side correlations at 7 Te. V. UF-IFT Seminar Gainesville, FL, November 19, 2010 UE&MB@CMS Rick Field – Florida/CDF/CMS 1

QCD Monte-Carlo Models: High Transverse Momentum Jets “Hard Scattering” Component “Underlying Event” Æ Start with the perturbative 2 -to-2 (or sometimes 2 -to-3) parton-parton scattering and add initial and finalstate gluon radiation (in the leading log approximation or modified leading log approximation). Æ 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“jet” an unavoidable Æ Of course the outgoing colored partons fragment into hadron and inevitably “underlying event” background to most collider observables and observables receive contributions from initial and final-state radiation. having good understand of it leads to more precise collider measurements! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 2

MPI, Pile-Up, and Overlap MPI: Multiple Parton Interactions Pile-Up Proton Æ MPI: Additional 2 -to-2 parton-parton scatterings within a single hadron-hadron collision. Proton Interaction Region Dz Æ Pile-Up: More than one hadron-hadron collision in the beam crossing. Overlap Æ Overlap: An experimental timing issue where a hadron-hadron collision from the next beam crossing gets included in the hadron collision from the current beam crossing because the next crossing happened before the event could be read out. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 3

Traditional Approach CDF Run 1 Analysis Charged Particle Df Correlations PT > PTmin |h| < hcut “Transverse” region very sensitive to the “underlying event”! Leading Calorimeter Jet or Leading Charged Particle or Z-Boson Æ Look at charged particle correlations in the azimuthal angle Df relative to a leading object (i. e. Calo. Jet#1, Chg. Jet#1, PTmax, Z-boson). For CDF PTmin = 0. 5 Ge. V/c hcut = 1. Æ Define |Df| < 60 o as “Toward”, 60 o < |Df| < 120 o as “Transverse”, and |Df| > 120 o as “Away”. Æ All three regions have the same area in h-f space, Dh×Df = 2 hcut× 120 o = 2 hcut× 2 p/3. Construct densities by dividing by the area in h-f space. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 4

CMS UE Analyses Traditional Approach Now published in EPJC! Æ Uncorrected data on the “transverse” region as defined by the leading track, PTmax, and the leading charged particle jet, PT(chgjet#1) at 900 Ge. V (p. T > 0. 5 Ge. V/c, |h| < 2. 0) compared with several QCD Monte-Carlo models after detector simulation. Æ Uncorrected data on the “transverse” region as defined by the leading charged particle jet, PT(chgjet#1) at 7 Te. V and 900 Ge. V (p. T > 0. 5 Ge. V/c, |h| < 2. 0) compared with several QCD Monte-Carlo models after detector simulation. UE&MB@CMS UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 5

CMS UE Analyses New Approach Method proposed by Gavin Salam et. al. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 6

ATLAS UE Analysis Æ Corrected data on the “towards”, “away”, and “transverse” regions as defined by the leading track, PTmax, at 7 Te. V and 900 Ge. V (p. T > 0. 5 Ge. V/c, |h| < 2. 5) compared with several QCD Monte-Carlo models at the generator level. Traditional Approach UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 7

“Transverse” Charged Particle Density Leading Charged Particle Jet, chgjet#1. Prediction! Æ Fake data (from MC) at 900 Ge. V on the “transverse” charged particle density, d. N/dhdf, as defined by the leading charged particle (PTmax) and the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/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 Ge. V (361, 595 events in the plot). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS Leading Charged Particle, PTmax. Rick Field MB&UE@CMS Workshop CERN, November 6, 2009 8

“Transverse” Charged Particle Density Æ Fake data (from MC) at 900 Ge. V on the Æ CMS preliminary data at 900 Ge. V on the “transverse” charged particle density, d. N/dhdf, as defined by the leading charged particle (PTmax) and the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. The fake with p. T > 0. 5 Ge. V/c and |h| < 2. The data are data (from PYTHIA Tune DW) are uncorrected and compared with PYTHIA generated at the particle level (i. e. generator Tune DW after detector simulation (216, 215 level) assuming 0. 5 M min-bias events at 900 events in the plot). Ge. V (361, 595 events in the plot). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 9

“Transverse” Charged PTsum Density Æ Fake data (from MC) at 900 Ge. V on the Æ CMS preliminary data at 900 Ge. V on the “transverse” charged PTsum density, d. PT/dhdf, as defined by the leading charged particle (PTmax) and the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. The fake data with p. T > 0. 5 Ge. V/c and |h| < 2. The data are (from PYTHIA Tune DW) are generated at uncorrected and compared with PYTHIA the particle level (i. e. generator level) Tune DW after detector simulation (216, 215 assuming 0. 5 M min-bias events at 900 Ge. V events in the plot). (361, 595 events in the plot). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 10

PYTHIA Tune DW Æ CMS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged particle density, d. N/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 11

PYTHIA Tune DW Æ ATLAS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged particle density, d. N/dhdf, as defined by the leading charged particle (PTmax) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. 5. The data are corrected and compared with PYTHIA Tune DW at the generator level. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 12

PYTHIA Tune DW CMS ATLAS Æ CMS preliminary data at 900 Ge. V and 7 Te. V Æ ATLAS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged particle density, d. N/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with particle (PTmax) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. 5. The data are corrected p. T > 0. 5 Ge. V/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW at the generator level. DW after detector simulation. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 13

PYTHIA Tune DW CMS Æ CMS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged PTsum density, d. PT/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. UF-IFT Seminar Gainesville, FL, November 19, 2010 ATLAS Æ ATLAS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged PTsum density, d. PT/dhdf, as defined by the leading charged particle (PTmax) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. 5. The data are corrected and compared with PYTHIA Tune DW at the generator level. Rick Field – Florida/CDF/CMS 14

“Transverse” Charge Density Rick Field MB&UE@CMS Workshop CERN, November 6, 2009 factor of 2! Prediction! LHC 900 Ge. V → 7 Te. V (UE increase ~ factor of 2) ~0. 4 → ~0. 8 LHC 7 Te. V Æ Shows the charged particle density in the “transverse” region for charged particles (p. T > 0. 5 Ge. V/c, |h| < 2) at 900 Ge. V and 7 Te. V as defined by PTmax from PYTHIA Tune DW and at the particle level (i. e. generator level). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 15

PYTHIA Tune DW Ratio CMS Æ CMS preliminary data at 900 Ge. V and 7 Te. V Æ Ratio of CMS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged particle density, d. N/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 16

PYTHIA Tune DW CMS ATLAS Æ Ratio of CMS preliminary data at 900 Ge. V Æ Ratio of the ATLAS preliminary data at and 7 Te. V on the “transverse” charged 900 Ge. V and 7 Te. V on the “transverse” particle density, d. N/dhdf, as defined by the charged particle density, d. N/dhdf, as leading charged particle jet (chgjet#1) for defined by the leading charged particles with p. T > 0. 5 Ge. V/c and |h| (PTmax) for charged particles with p. T > 0. 5 < 2. The data are uncorrected and compared Ge. V/c and |h| < 2. 5. The data are corrected with PYTHIA Tune DW after detector and compared with PYTHIA Tune DW at simulation. the generator level. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 17

PYTHIA Tune DW CMS Æ Ratio of the CMS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged PTsum density, d. PT/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation. UF-IFT Seminar Gainesville, FL, November 19, 2010 ATLAS Æ Ratio of the ATLAS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged PTsum density, d. PT/dhdf, as defined by the leading charged particle (PTmax) for charged particles with p. T > 0. 5 Ge. V/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

“Transverse” Multiplicity Distribution Same hard scale at two different center-ofmass energies! CMS Æ CMS uncorrected data at 900 Ge. V and 7 Te. V on the charged particle multiplicity distribution in the “transverse” region for charged particles (p. T > 0. 5 Ge. V/c, |h| < 2) as defined by the leading charged particle jet, chgjet#1, with PT(chgjet#1) > 3 Ge. V/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. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 19

“Transverse” Multiplicity Distribution Same center-of-mass energy at two different hard scales! CMS Æ CMS uncorrected data at 7 Te. V on the charged particle multiplicity distribution in the “transverse” region for charged particles (p. T > 0. 5 Ge. V/c, |h| < 2) as defined by the leading charged particle jet, chgjet#1, with PT(chgjet#1) > 3 Ge. V/c and PT(chgjet#1) > 20 Ge. V/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. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 20

PYTHIA Tune DW How well did we do at predicting the “underlying event” at 900 Ge. V and 7 Te. V? Tune DW ÆI am surprised that the Tunes did not do a better job of predicting the behavior of the “underlying event” at 900 Ge. V and 7 Te. V! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS Tune DW 21

PYTHIA Tune DW How well did we do at predicting the “underlying event” at 900 Ge. V and 7 Te. V? Tune DW ÆI am surprised that the Tunes did as well as they did at predicting the behavior of the “underlying event” at 900 Ge. V and 7 Te. V! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS Tune DW 22

UE Summary Æ The “underlying event” at 7 Te. V and 900 Ge. V is almost what we expected! With a little tuning we should be able to describe the data very well (see Tune Z 1 later in this talk). Warning! All the UE studies look at charged particles with p. T > 0. 5 Ge. V/c. ÆI am surprised that. We thedo. Tunes did as well as not know if the models correctly they did at predictingdescribe the behavior the p. T values! the UE atof lower “underlying event” at 900 Ge. V and 7 Te. V! Remember this is “soft” QCD! Æ“Min-Bias” is a whole different story! Much more complicated due to very soft particles and diffraction! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS PARP(82) PARP(90) Color Diffraction Connections 23

Rick Field University of Chicago July 11, 2006 “Leading Jet” “Back-to-Back” Neither PY Tune A or HERWIG fits the ETsum density in the “transferse” region! HERWIG does slightly better than Tune A! Æ Shows the data on the tower ETsum density, d. ETsum/dhdf, in the “trans. MAX” and “trans. MIN” region (ET > 100 Me. V, |h| < 1) versus PT(jet#1) for “Leading Jet” and “Back-to-Back” events. Æ Compares the (corrected) data with PYTHIA Tune A (with MPI) and HERWIG (without MPI) at the particle level (all particles, |h| < 1). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 24

Rick Field University of Chicago July 11, 2006 Possible Scenario? ? Æ PYTHIA Tune A fits the charged particle PTsum density for p. T > 0. 5 Ge. V/c, but it does not produce enough ETsum for towers with ET > 0. 1 Ge. V. Æ It is possible that there is a sharp rise in the number of particles in the “underlying event” at low p. T (i. e. p. T < 0. 5 Ge. V/c). Æ Perhaps there are two components, a vary “soft” beam-beam remnant component (Gaussian or exponential) and a “hard” multiple interaction component. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 25

Proton-Proton Collisions stot = s. EL + s. SD IN + s. DD + s. HC ND “Inelastic Non-Diffractive Component” The “hard core” component contains both “hard” and “soft” collisions. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 26

The Inelastic Non-Diffractive Cross-Section Occasionally one of the parton-parton collisions is hard (p. T > ≈2 Ge. V/c) Majority of “minbias” events! “Semi-hard” parton collision (p. T < ≈2 Ge. V/c) + +… UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS Multiple-parton interactions (MPI)! 27

The “Underlying Event” Select inelastic non-diffractive events that contain a hard scattering Hard parton-parton collisions is hard (p. T > ≈2 Ge. V/c) 1/(p. T)4→ 1/(p. T 2+p. T 02)2 The “underlying-event” (UE)! “Semi-hard” parton collision (p. T < ≈2 Ge. V/c) + Given that you have one hard scattering it is more probable to have MPI! Hence, the UE has more activity than “min-bias”. UF-IFT Seminar Gainesville, FL, November 19, 2010 + Rick Field – Florida/CDF/CMS +… Multiple-parton interactions (MPI)! 28

Allow leading hard scattering to go to zero p. T with same cut -off as the MPI! Model of s. ND 1/(p. T)4→ 1/(p. T 2+p. T 02)2 Model of the inelastic nondiffractive cross section! “Semi-hard” parton collision (p. T < ≈2 Ge. V/c) + +… UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS Multiple-parton interactions (MPI)! 29

UE Tunes Allow primary hard-scattering to go to p. T = 0 with same cut-off! “Underlying Event” Fit the “underlying event” in a hard scattering process. All of Rick’s tunes (except X 2): 1/(p. T)4→ 1/(p. T 2+p. T 02)2 A, AWT, DWT, D 6 T, CW, X 1, “Min-Bias” (add (ND)single & double diffraction) and Tune Z 1, are UE tunes! + Predict MB (ND)! Predict MB (IN)! + + +… UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 30

Charged Particle Multiplicity No MPI! Tune A! Æ Data at 1. 96 Te. V on the charged particle multiplicity (p. T > 0. 4 Ge. V/c, |h| < 1) for “min-bias” collisions at CDF Run 2 (non-diffractive cross-section). Æ The data are compared with PYTHIA Tune A and Tune A without multiple parton interactions (py. Ano. MPI). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 31

PYTHIA Tune A Min-Bias “Soft” + ”Hard” Ten decades! 12% of “Min-Bias” events have PT(hard) > 5 Ge. V/c! 1% of “Min-Bias” events have PT(hard) > 10 Ge. V/c! Lots of “hard” scattering in “Min-Bias” at the Tevatron! Æ Comparison of PYTHIA Tune A with the p. T distribution of charged particles for “min-bias” collisions at CDF Run 1 (non-diffractive cross-section). p. T = 50 Ge. V/c! Æ 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 Ge. V/c (1% with PT(hard) > 10 Ge. V/c)! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 32

CDF: Charged p. T Distribution Erratum November 18, 2010 Excess No excess events atat large p. Tp! T! 50 Ge. V/c! Æ Published CDF data on the p. T distribution of charged particles in Min-Bias collisions (ND) at 1. 96 Te. V compared with PYTHIA Tune A. UF-IFT Seminar Gainesville, FL, November 19, 2010 CDFinconsistent with. CMSand and. UA 1! Rick Field – Florida/CDF/CMS 33

MB Tunes “Underlying Event” Predict the “underlying event” in a hard scattering process! Most of Peter Skand’s tunes: S 320 Perugia 0, S 325 Perugia X, “Min-Bias” (ND) S 326 Perugia 6 are MB tunes! + Fit MB (ND). + + +… UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 34

MB+UE Tunes “Underlying Event” Fit the “underlying event” in a hard scattering process! Most of Hendrik’s “Professor” tunes: Pro. Q 20, P 329 are MB+UE! Simultaneous fit to both MB & UE “Min-Bias” (ND) + Fit MB (ND). + +… UF-IFT Seminar Gainesville, FL, November 19, 2010 + The ATLAS AMBT 1 Tune is an MB+UE tune, but because they include in the fit the ATLAS UE data with PTmax > 10 Ge. V/c (big errors) the LHC UE data does not have much pull (hence mostly an MB tune!). Rick Field – Florida/CDF/CMS 35

LHC MB Predictions: 900 Ge. V Off by 11%! Æ Compares the 900 Ge. V ALICE data with PYTHIA Tune DW and Tune S 320 Perugia 0. Tune DW uses the old Q 2 -ordered parton shower and the old MPI model. Tune S 320 uses the new p. T-ordered parton shower and the new MPI model. The numbers in parentheses are the average value of d. N/dh for the region |h| < 0. 6. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 36

ATLAS INEL d. N/dh Æ None of the tunes fit the ATLAS INEL d. N/dh data with PT > 100 Me. V! They all predict too few particles. Off by 20 -50%! Æ The ATLAS Tune AMBT 1 was designed to fit the inelastic data for Nchg ≥ 6 with p. T > 0. 5 Ge. V/c! UF-IFT Seminar Gainesville, FL, November 19, 2010 Soft particles! Rick Field – Florida/CDF/CMS 37

PYTHIA Tune DW If one increases the p. T the agreement improves! Tune DW Æ ALICE inelastic data at 900 Ge. V on the d. N/dh distribution for charged particles (p. T > PTmin) for events with at least one charged particle with p. T > PTmin and |h| < 0. 8 for PTmin = 0. 15 Ge. V/c, 0. 5 Ge. V/c, and 1. 0 Ge. V/c compared with PYTHIA Tune DW at the generator level. The same thing occurs at 7 Te. V! ALICE, ATLAS, and CMS data coming soon. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 38

PYTHIA Tune DW Diffraction contributes less at harder scales! Tune DW Æ ALICE inelastic data at 900 Ge. V on the d. N/dh distribution for charged particles (p. T > PTmin) for events with at least one charged particle with p. T > PTmin and |h| < 0. 8 for PTmin = 0. 15 Ge. V/c, 0. 5 Ge. V/c, and 1. 0 Ge. V/c compared with PYTHIA Tune Z 1 at the generator level (dashed = ND, solid = INEL). Cannot trust PYTHIA 6. 2 modeling of diffraction! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 39

CMS d. N/dh CMS Tune DW Soft particles! Okay if the Monte-Carlo does not fit the data what do we do? All p. T We tune the Monte-Carlo to fit the data! Be careful not to tune away new physics! Æ Generator level d. N/dh (all p. T). Shows the NSD = HC + DD and the HC = ND contributions for Tune DW. Also shows the CMS NSD data. Off by 50%! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 40

PYTHIA Tune Z 1 ÆAll my previous tunes (A, DWT, D 6, D 6 T, CW, X 1, and X 2) were PYTHIA 6. 4 tunes using the old Q 2 -ordered parton showers and the old MPI model (really 6. 2 tunes)! ÆI believe that it is time to move to PYTHIA 6. 4 (p. T-ordered parton showers and new MPI model)! ÆTune Z 1: I started with the parameters of ATLAS Tune AMBT 1, but I changed LO* to CTEQ 5 L and I varied PARP(82) and PARP(90) to get a very good fit of the CMS UE data at 900 Ge. V and 7 Te. V. Æ The ATLAS Tune AMBT 1 was designed to fit the inelastic data for Nchg ≥ 6 and to fit the PTmax UE data with PTmax > 10 Ge. V/c. Tune AMBT 1 is primarily a min-bias tune, while Tune Z 1 is a UE tune! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS PARP(90) PARP(82) Color Connections Diffraction UE&MB@CMS 41

PYTHIA Tune Z 1 (R. Field CMS) Tune AMBT 1 (ATLAS) CTEQ 5 L LO* PARP(82) – MPI Cut-off 1. 932 2. 292 PARP(89) – Reference energy, E 0 1800. 0 PARP(90) – MPI Energy Extrapolation 0. 275 0. 25 PARP(77) – CR Suppression 1. 016 PARP(78) – CR Strength 0. 538 0. 1 PARP(83) – Matter fraction in core 0. 356 PARP(84) – Core of matter overlap 0. 651 PARP(62) – ISR Cut-off 1. 025 PARP(93) – primordial k. T-max 10. 0 MSTP(81) – MPI, ISR, FSR, BBR model 21 21 MSTP(82) – Double gaussion matter distribution 4 4 MSTP(91) – Gaussian primordial k. T 1 1 MSTP(95) – strategy for color reconnection 6 6 Parameter Parton Distribution Function Parameters not shown are the PYTHIA 6. 4 defaults! PARP(80) – Probability colored parton from BBR UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 42

PYTHIA Tune Z 1 CMS Tune Z 1 Æ CMS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged particle density, d. N/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. 0. The data are uncorrected and compared with PYTHIA Tune DW and D 6 T after detector simulation Tune Z 1 after detector simulation (SIM). Color reconnection suppression. Color reconnection strength. UF-IFT Seminar Gainesville, FL, November 19, 2010 Tune Z 1 (CTEQ 5 L) PARP(82) = 1. 932 PARP(90) = 0. 275 PARP(77) = 1. 016 PARP(78) = 0. 538 Rick Field – Florida/CDF/CMS Tune Z 1 is a PYTHIA 6. 4 using p. T-ordered parton showers and the new MPI model! 43

PYTHIA Tune Z 1 CMS Tune Z 1 Æ CMS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged PTsum density, d. PT/dhdf, as defined by the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. 0. The data are uncorrected and compared with PYTHIA Tune DW and D 6 T after detector simulation Tune Z 1 after detector simulation (SIM). Color reconnection suppression. Color reconnection strength. UF-IFT Seminar Gainesville, FL, November 19, 2010 Tune Z 1 (CTEQ 5 L) PARP(82) = 1. 932 PARP(90) = 0. 275 PARP(77) = 1. 016 PARP(78) = 0. 538 Rick Field – Florida/CDF/CMS Tune Z 1 is a PYTHIA 6. 4 using p. T-ordered parton showers and the new MPI model! 44

PYTHIA Tune Z 1 ATLAS Tune Z 1 Æ ATLAS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged particle density, d. N/dhdf, as defined by the leading charged particle (PTmax) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. 5. The data are corrected and compared with PYTHIA Tune Z 1 at the generator level. Color reconnection suppression. Color reconnection strength. UF-IFT Seminar Gainesville, FL, November 19, 2010 ATLAS Æ ATLAS preliminary data at 900 Ge. V and 7 Te. V on the “transverse” charged PTsum density, d. PT/dhdf, as defined by the leading charged particle (PTmax) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. 5. The data are corrected and compared with PYTHIA Tune Z 1 at the generrator level. Tune Z 1 (CTEQ 5 L) PARP(82) = 1. 932 PARP(90) = 0. 275 PARP(77) = 1. 016 PARP(78) = 0. 538 Rick Field – Florida/CDF/CMS Tune Z 1 is a PYTHIA 6. 4 using p. T-ordered parton showers and the new MPI model! 45

PYTHIA Tune Z 1 CMS Æ Ratio of CMS preliminary data at 900 Ge. V and 7 Te. V (7 Te. V divided by 900 Ge. V) on the “transverse” charged particle density as defined by the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. 0. The data are uncorrected and compared with PYTHIA Tune DW, D 6 T, CW, and P 0 after detector Tune Z 1 after detector simulation (SIM). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 46

PYTHIA Tune Z 1 CMS Æ Ratio of CMS preliminary data at 900 Ge. V and 7 Te. V (7 Te. V divided by 900 Ge. V) on the “transverse” charged PTsum density as defined by the leading charged particle jet (chgjet#1) for charged particles with p. T > 0. 5 Ge. V/c and |h| < 2. 0. The data are uncorrected and compared with PYTHIA Tune DW, D 6 T, CW, and P 0 after detector Tune Z 1 after detector simulation (SIM). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 47

PYTHIA Tune Z 1 ATLAS Æ Ratio of the ATLAS preliminary data on the charged particle density in the “transverse” region for charged particles (p. T > 0. 5 Ge. V/c, |h| < 2. 5) at 900 Ge. V and 7 Te. V as defined by PTmax compared with PYTHIA Tune Z 1 at the generator level. UF-IFT Seminar Gainesville, FL, November 19, 2010 ATLAS Æ Ratio of the ATLAS preliminary data on the charged PTsum density in the “transverse” region for charged particles (p. T > 0. 5 Ge. V/c, |h| < 2. 5) at 900 Ge. V and 7 Te. V as defined by PTmax compared with PYTHIA Tune Z 1 at the generator level. Rick Field – Florida/CDF/CMS 48

“Transverse” Multiplicity Distribution Same hard scale at two different center-ofmass energies! CMS Tune Z 1 Difficult to produce Æ CMS uncorrected data at 900 Ge. V and 7 Te. V on Æ CMS uncorrected data at 900 Ge. V and 7 enough events with Te. V on the charged particle multiplicity distribution in large “transverse” the “transverse” region for charged particles (p. T > distribution in the “transverse” region multiplicity low. Ge. V/c, |h| for charged particles (p. T at > 0. 5 Ge. V/c, |h| < 2) as defined by the leading hard < 2) as defined by the scale! leading charged particle jet with PT(chgjet#1) > 3 Ge. V/c compared with PYTHIA Tune DW and Tune D 6 T particle jet with PT(chgjet#1) > 3 Ge. V/c compared with PYTHIA Tune Z 1 at the detector level (i. e. Theory + SIM). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 49

“Transverse” PTsum Distribution Same hard scale at two different center-ofmass energies! CMS Tune Z 1 Æ CMS uncorrected data at 900 Ge. V and 7 Te. V Difficult to produce on the charged scalar PTsum distribution in enough events with the “transverse” region for charged particles large “transverse” (p. T > 0. 5 Ge. V/c, |h| < 2) as defined by the PTsum leading charged particle jet with PT(chgjet#1) leading charged particleat jetlow with PT(chgjet#1) hard scale! > 3 Ge. V/c compared with PYTHIA Tune Z 1, DW, and Tune D 6 T at the detector level (i. e. Theory + SIM). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 50

“Transverse” Multiplicity Distribution CMS Same center-of-mass energy at two different hard scales! CMS Tune Z 1 Difficult Æ CMS uncorrected datatoatproduce 7 Te. V on the Æ CMS uncorrected data at 7 Te. V on the enough events with charged particle multiplicity distribution in large “transverse” region for charged particles the “transverse” multiplicity low by the (p. T > 0. 5 Ge. V/c, |h| < 2) as at defined (p. T > 0. 5 Ge. V/c, |h| < 2) as defined by the hard scale! jet with PT(chgjet#1) leading charged particle > 3 Ge. V/c and PT(chgjet#1) > 20 Ge. V/c compared with PYTHIA Tune DW and Tune compared with PYTHIA Tune Z 1 at the D 6 T at the detector level (i. e. Theory + SIM). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 51

“Transverse” PTsum Distribution Same center-of-mass energy at two different hard scales! CMS Tune Z 1 Æ CMS uncorrected data at 7 Te. V on the charged Difficultintothe produce PTsum distribution “transverse” region for PTsum distribution in the “transverse” region enough events with |h| < 2) as for charged particles (p. T > 0. 5 Ge. V/c, |h| < 2) as charged particles (p. T > 0. 5 Ge. V/c, “transverse” defined by thelarge leading charged particle jet with defined by the leading charged particle jet with PTsum low. PT(chgjet#1) > 20 PT(chgjet#1) > 3 Ge. V/catand PT(chgjet#1) > 3 Ge. V/c and PT(chgjet#1) > 20 Ge. V/c comparedhard with scale! PYTHIA Tune Z 1 at the Ge. V/c compared with PYTHIA Tune DW and detector level (i. e. Theory + SIM). Tune D 6 T at the detector level (i. e. Theory + SIM). UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 52

CMS d. N/dh Tune Z 1 CMS Æ Generator level d. N/dh (all p. T). Shows the NSD = HC + DD and the HC = ND contributions for Tune Z 1. Also shows the CMS NSD data. Æ Generator level d. N/dh (all p. T). Shows the NSD = HC + DD prediction for Tune Z 1 and Tune X 2. Also shows the CMS NSD data. Okay not perfect, but remember we do not know if the DD is correct! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 53

PYTHIA Tune Z 1 Æ ALICE inelastic data at 900 Ge. V on the d. N/dh distribution for charged particles (p. T > PTmin) for events with at least one charged particle with p. T > PTmin and |h| < 0. 8 for PTmin = 0. 15 Ge. V/c, 0. 5 Ge. V/c, and 1. 0 Ge. V/c compared with PYTHIA Tune Z 1 at the generator level. Okay not perfect, but remember we do not know if the SD & DD are correct! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 54

NSD Multiplicity Distribution CMS Difficult to produce enough events with large multiplicity! Tune Z 1 Æ Generator level charged multiplicity distribution (all p. T, |h| < 2) at 900 Ge. V and 7 Te. V. Shows the NSD = HC + DD prediction for Tune Z 1. Also shows the CMS NSD data. Okay not perfect! But not that bad! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 55

MB & UE “Min-Bias” CMS Tune Z 1 “Underlying Event” Tune Z 1 Difficult to produce enough events with large multiplicity! Æ Generator level charged multiplicity distribution (all p. T, |h| < 2) at 900 Ge. V and 7 Te. V. Shows the NSD = HC + DD prediction for Tune Z 1. Also shows the CMS NSD data. UF-IFT Seminar Gainesville, FL, November 19, 2010 Æ CMS uncorrected Difficult datatoatproduce 900 Ge. V and 7 Te. V on the charged enoughparticle events with multiplicity distribution inlarge the “transverse”region for charged particles multiplicity (p. T >at 0. 5 low Ge. V/c, |h| < 2) as defined byhard the leading scale! charged particle jet with PT(chgjet#1) > 3 Ge. V/c compared with PYTHIA Tune Z 1 at the detector level (i. e. Theory + SIM). Rick Field – Florida/CDF/CMS 56

MB & UE CMS Tune Z 1 Æ CMS uncorrected data at 7 Te. V on the charged particle multiplicity distribution in the “transverse” region for charged particles (p. T > 0. 5 Ge. V/c, |h| < 2) as defined by the leading charged particle jet with PT(chgjet#1) > 20 Ge. V/c compared with PYTHIA Tune Z 1 at the detector level (i. e. Theory + SIM). Also shows the CMS corrected NSD multiplicity distribution (all p. T, |h| < 2) compared with Tune Z 1 at the generator. Amazing what we are asking the Monte-Carlo models to fit! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 57

Two Particle Angular Correlations Æ Signal, S, is two particles in the same event. Æ Background, B, is two particles in two different events. Æ Correlation, R, is ~(S-B)/B. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 58

Two Particle Angular Correlations CMS “min-bias” 7 Te. V UF-IFT Seminar Gainesville, FL, November 19, 2010 Bose-Einstein Rick Field – Florida/CDF/CMS 59

High Multiplicity at 7 Te. V Select Events with High Multiplicity UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 60

Two Particle Angular Correlations High Multiplicity “Min-Bias” Average “Min-Bias” ÆLots of jets at high multiplicity! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 61

Two Particle Angular Correlations Average “Min-Bias” UF-IFT Seminar Gainesville, FL, November 19, 2010 High Multiplicity “Min-Bias” Rick Field – Florida/CDF/CMS 62

Long-Range Same-Side Correlations High Multiplicity “Min-Bias” Not there in PYTHIA 8! Also not there in PYTHIA 6 and HERWIG++! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 63

Correlation in Heavy Ion Collisions ÆLong range correlations expected in “collective flow” in heavy ion collisions. UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 64

Correlation in Heavy Ion Collisions ÆLong-range “Ridge”-like structure in Dh at Df ≈ 0! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 65

Proton-Proton vs Au-Au Proton-Proton Collisions 7 Te. V Gold-Gold Collisions 200 Ge. V QGP ÆI am not ready to jump on the quarkgluon plasma bandwagon quite yet! UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 66

Jet-Jet Correlations Æ Are the “leading-log” or “modified leading-log” QCD Monte-Carlo Models missing an important QCD correlation? Æ The leading jet and the incident protons form a plane (yz-plane in the figure). This is the plane of the hard scattering. Æ Initial & final-state radiation prefers to lie in this plane. This is a higher order effect that you can see in the 2→ 3 or 2→ 4 matrix elements, but it is not there if you do 2→ 2 matrix elements and then add radiation using a naïve leading log approximation (i. e. independent emission). Æ I do not know to what extent this higher order jet-jet correlation is incorporated in the QCD Monte-Carlo models. Æ I would think that this jet-jet correlation would produce a long range (in Dh) correlation with Df ≈ 0 from two particles with one in the leading jet and one in the radiated jet. Why don’t we see this in the Monte-Carlo models? UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 67

Jet-Jet Correlations Æ Initial & Final-State Radiation: There should be more particles “in-the-plane” of the hard scattering (yz-plane in the figure) than “out-of –the-plane”. ? ? Æ I do not understand why this does not result in a long-range same-side correlation? UF-IFT Seminar Gainesville, FL, November 19, 2010 Rick Field – Florida/CDF/CMS 68

Min-Bias Summary no. e. i nt( i n e m e “will lfit t ev that r fmodel ÆWe are a long way from having a Monte-Carlo s! all the o o s e m d a e o m o b soft uceare smore is t eparticles features of the LHC min-bias data! There that d t h o a t r m p wh by ee o s t a d e e e s expected! id el er ict d h o d o T n e ta. r m e. a p v y o d t l a P h an ÆWe need a better understanding of. Idiffraction! ar tiplici and tmodeling h E C L ! e cles ned by ont ge mul t 7 Te. V i t r M pa strai he a lar ents a t e g r fo v an e con h t e r t i l t t s u f w ar gh ffic scale) city so s i l u e d o od en li t is hard p e m i c t l o u du Carl e n o m g PARP(82 r r ctio h p a a ) g l r e t f i h Dif no Mont ” o s a d bi els ! The d o m here e h ÆT ing on or go Col ) 90 ( RP PA ons C ecti onn ida/ ield F Rick b ar min , Novem e S L FT 0 9, 2 er 1 10 or – Fl MS /C CDF 69

The LHC in 2011 Æ Beam back around 21 st February. Æ Beam back around on February 21 st! Æ 2 weeks re-commissioning with beam (at least). technical stop every 6 weeks. ThisÆis 4 day fun! Æ 4 weeks ion run. Æ End of run – December 12 th. Æ Approximately 200 days proton physics! Æ Maybe 8 Te. V (4 Te. V/beam). Peak luminosity UF-IFT Seminar Gainesville, FL, November 19, 2010 6. 4 x 1032 Integrated per day 11 pb-1 200 days 2. 2 fb-1 Stored energy 72 MJ Rick Field – Florida/CDF/CMS 70