LHC First Data

LHC2010 Conference at Michigan Ann Arbor MI, December 12, 2010

Rick Field – Florida/CDF/CMS Page 1

LHC First DataLHC First Data

Rick FieldUniversity 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.

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).

Monte-Carlo Models Facing Real Data

CMS

ATLAS

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

Proton Proton

“Minimum Bias” Collisions



QCD Monte-Carlo Models:QCD Monte-Carlo Models:High Transverse Momentum JetsHigh Transverse Momentum Jets

Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and final-state gluon radiation (in the leading log approximation or modified leading log approximation).

Hard Scattering

PT(hard)

Outgoing Parton

Outgoing Parton



Hard Scattering

PT(hard)

Outgoing Parton

Outgoing Parton



Proton AntiProton


Proton AntiProton


“Hard Scattering” Component

“Jet”

“Jet”

“Underlying Event”

The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or semi-soft multiple parton interactions (MPI).

Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event” observables receive contributions from initial and final-state radiation.

“Jet”

The “underlying event” is an unavoidable background to most collider observables and having good understand of it leads to

more precise collider measurements!



Traditional ApproachTraditional Approach

Look at charged particle correlations in the azimuthal angle relative to a leading object (i.e. CaloJet#1, ChgJet#1, PTmax, Z-boson). For CDF PTmin = 0.5 GeV/c cut = 1.

Charged Particle Correlations PT > PTmin || < cut

Leading Object Direction

“Toward”

“Transverse” “Transverse”

“Away”

Define || < 60o as “Toward”, 60o < || < 120o as “Transverse”, and || > 120o as “Away”.

Leading Calorimeter Jet or Leading Charged Particle Jet or

Leading Charged Particle orZ-Boson

-cut +cut

2

0

Leading Object

Toward Region

Transverse Region

Transverse Region

Away Region

Away Region

All three regions have the same area in - space, × = 2cut×120o = 2cut×2/3. Construct densities by dividing by the area in - space.

Charged Jet #1Direction


“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

“Transverse” region very sensitive to the “underlying event”!

CDF Run 1 Analysis



““Transverse” Charged Particle DensityTransverse” Charged Particle Density

Fake data (from MC) at 900 GeV on the “transverse” charged particle density, dN/dd, 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 || < 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).

PT(chgjet#1) Direction

“Toward”


“Away”

"Transverse" Charged Particle Density: dN/dd

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PTmax or PT(chgjet#1) (GeV/c)

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900 GeV

Charged Particles (||<2.0, PT>0.5 GeV/c)

RDF PreliminaryFake Data

pyDW generator levelChgJet#1

PTmax

Rick FieldMB&UE@CMS WorkshopCERN, November 6, 2009

PTmax Direction

“Toward”


“Away”

Leading Charged Particle Jet, chgjet#1.

Leading Charged Particle, PTmax.

Prediction!



““Transverse” Charged Particle DensityTransverse” Charged Particle Density

Fake data (from MC) at 900 GeV on the “transverse” charged particle density, dN/dd, 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 || < 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).


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pyDW generator levelChgJet#1

PTmax

CMS preliminary data at 900 GeV on the “transverse” charged particle density, dN/dd, 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 || < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation (216,215 events in the plot).


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data uncorrectedpyDW + SIM

900 GeV

ChgJet#1

PTmax

Charged Particles (||<2.0, PT>0.5 GeV/c) Real Data!Monte-Carlo!



““Transverse” Charged PTsum DensityTransverse” Charged PTsum Density

"Transverse" Charged PTsum Density: dPT/dd

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PT

su

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en

sity

(G

eV

/c)

900 GeV


ChgJet#1

PTmax


pyDW generator level

Fake data (from MC) at 900 GeV on the “transverse” charged PTsum density, dPT/dd, 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 || < 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).


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PT

sum

Den

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CMS Preliminarydata uncorrected

pyDW + SIM

900 GeV


ChgJet#1

PTmax

CMS preliminary data at 900 GeV on the “transverse” charged PTsum density, dPT/dd, 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 || < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation (216,215 events in the plot).

Real Data!Monte-Carlo!



PYTHIA Tune DWPYTHIA Tune DW

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


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PT(chgjet#1) GeV/c

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900 GeV


pyDW + SIM


7 TeV


“Toward”


“Away”



PYTHIA Tune DWPYTHIA Tune DW"Transverse" Charged Particle Density: dN/dd

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PTmax (GeV/c)

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sity RDF Preliminary

ATLAS corrected dataTune DW generator level

900 GeV

7 TeV


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

PTmax Direction

“Toward”


“Away”

ATLAS Note: ATLAS-CONF-2010-029May 29, 2010

I read the points off with a ruler!




PTmax Direction

“Toward”


“Away”


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PTmax (GeV/c)

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ATLAS corrected dataTune DW generator level

900 GeV

7 TeV


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



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900 GeV


pyDW + SIM


7 TeV

CMS ATLAS


“Toward”


“Away”




CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and || < 2. The data are uncorrected and compared with PYTHIA Tune DW after detector simulation.

ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 2.5. The data are corrected and compared with PYTHIA Tune DW at the generator level.


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GeV

/c)


pyDW + SIM


900 GeV

7 TeV


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sum

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RDF PreliminaryATLAS corrected data

Tune DW generator level

900 GeV

7 TeV


CMS ATLAS

PTmax Direction

“Toward”


“Away”


“Toward”


“Away”



““Transverse” Charge DensityTransverse” Charge Density

PTmax Direction

“Toward”


“Away”

PTmax Direction

“Toward”


“Away”

LHC 900 GeV

LHC7 TeV

900 GeV → 7 TeV (UE increase ~ factor of 2)


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RDF Preliminarypy Tune DW generator level

900 GeV

7 TeV

Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2) at 900 GeV and 7 TeV as defined by PTmax from PYTHIA Tune DW and at the particle level (i.e. generator level).

factor of 2!

~0.4 → ~0.8

Rick FieldMB&UE@CMS WorkshopCERN, November 6, 2009

Prediction!




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


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pyDW + SIM

Charged Particles (||<2.0, PT>0.5 GeV/c) 7 TeV / 900 GeV

CMS


“Toward”


“Away”



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PT(chgjet#1) GeV/c

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arg

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900 GeV


pyDW + SIM


7 TeV

CMS


“Toward”


“Away”

Ratio




Ratio of CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dd, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and || < 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/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 2.5. The data are corrected and compared with PYTHIA Tune DW at the generator level.


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eV/9

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pyDW + SIM



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PTmax (GeV/c)

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eV/9

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eV


RDF PreliminaryATLAS corrected datapyDW generator level

7 TeV / 900 GeV

CMS ATLAS

PTmax Direction

“Toward”


“Away”


“Toward”


“Away”




Ratio of the CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and || < 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 PTsum density, dPT/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 2.5. The data are corrected and compared with PYTHIA Tune DW at the generator level.


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PTmax (GeV/c)

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RDF PreliminaryATLAS corrected datapyDW generator level

7 TeV / 900 GeV


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CMS ATLAS

PTmax Direction

“Toward”


“Away”


“Toward”


“Away”



““Transverse” Multiplicity DistributionTransverse” Multiplicity Distribution

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, || < 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).

Same hard scale at two different center-

of-mass energies!

Shows the growth of the “underlying event” as the center-of-mass energy increases.

"Transverse" Charged Particle Multiplicity

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

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Number of Charged Particles

Pro

bab

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y


pyDW + SIM

Normalized to 1


PT(chgjet#1) > 3 GeV/c

900 GeV 7 TeV

CMS PT(chgjet#1) Direction

“Toward”


“Away”




CMS uncorrected data at 7 TeV on the charged particle multiplicity distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 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).

Same center-of-mass energy at two different

hard scales!

Shows the growth of the “underlying event” as the hard scale increases.


1.0E-07

1.0E-06

1.0E-05

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1.0E-02

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Pro

bab

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pyDW + SIM

Normalized to 1


7 TeV



CMS


“Toward”


“Away”




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!

How well did we do at predicting the “underlying event” at 900 GeV and 7 TeV?


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Tune DW 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!

How well did we do at predicting the “underlying event” at 900 GeV and 7 TeV?


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Tune DW Tune DW

Tune DW



UE SummaryUE SummaryThe “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).

“Min-Bias” is a whole different story! Much more complicated due to very soft particles and diffraction!

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton




PARP(90)

Color

Connections

PARP(82)

Diffraction

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!

Warning! All the UE studies lookat charged particles with pT > 0.5 GeV/c.We do not know if the models correctly

describe the UE at lower pT values!



Proton-Proton CollisionsProton-Proton Collisions Elastic Scattering Single Diffraction

M

tot = ELSD DD HC

Double Diffraction

M1 M2

Proton Proton

“Soft” Hard Core (no hard scattering)

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton




“Hard” Hard Core (hard scattering)

Hard Core The “hard core” component

contains both “hard” and “soft” collisions.

“Inelastic Non-Diffractive Component”

NDtot = ELIN



The Inelastic Non-Diffractive The Inelastic Non-Diffractive Cross-SectionCross-Section

Proton Proton

Proton Proton +

Proton Proton

Proton Proton

+

Proton Proton +

+ …

“Semi-hard” parton-parton collision(pT < ≈2 GeV/c)

Occasionally one of the parton-parton collisions is hard(pT > ≈2 GeV/c)

Majority of “min-bias” events!

Multiple-parton interactions (MPI)!



The “Underlying Event”The “Underlying Event”

Proton Proton

Select inelastic non-diffractive events that contain a hard scattering

Proton Proton

Proton Proton +

Proton Proton

+ + …


Hard parton-parton collisions is hard(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”.

1/(pT)4→ 1/(pT2+pT0

2)2



Model of Model of NDND

Proton Proton

Proton Proton +

Proton Proton

Proton Proton

+

Proton Proton +

+ …


Allow leading hard scattering to go to zero pT with same cut-off as the MPI!

Model of the inelastic non-diffractive cross section!


Proton Proton

1/(pT)4→ 1/(pT2+pT0

2)2



UE TunesUE Tunes

Proton Proton

Proton Proton +

Proton Proton

Proton Proton

+

Proton Proton +

+ …


“Min-Bias” (ND)

Fit the “underlying event” in a hard

scattering process.

Predict MB (ND)!

1/(pT)4→ 1/(pT2+pT0

2)2

Allow primary hard-scattering to go to pT = 0 with same cut-off!

Single Diffraction

M

Double Diffraction

M1 M2

“Min-Bias” (add single & double diffraction)

Predict MB (IN)!

All of Rick’s tunes (except X2):A, AW, AWT,DW, DWT,

D6, D6T, CW, X1, and Tune Z1,are UE tunes!



Charged Particle MultiplicityCharged Particle Multiplicity

Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, || < 1) for “min-bias” collisions at CDF Run 2 (non-diffractive cross-section).

Charged Multiplicity Distribution

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CDF Run 2 <Nchg>=4.5

Normalized to 1

CDF Run 2 Preliminary

Min-Bias 1.96


i

Proton AntiProton


The data are compared with PYTHIA Tune A and Tune A without multiple parton interactions (pyAnoMPI).


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py Tune A <Nchg> = 4.3

pyAnoMPI <Nchg> = 2.6


CDF Run 2 Preliminary

Min-Bias 1.96 Normalized to 1

No MPI! Tune A!



PYTHIA Tune A Min-BiasPYTHIA Tune A Min-Bias“Soft” + ”Hard”“Soft” + ”Hard”

Comparison of PYTHIA Tune A with the pT distribution of charged particles for “min-bias” collisions at CDF Run 1 (non-diffractive cross-section).

Charged Particle Density

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d d

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(1/

GeV

/c)

Pythia 6.206 Set A

CDF Min-Bias Data

CDF Preliminary

1.8 TeV ||<1

PT(hard) > 0 GeV/c12% of “Min-Bias” events have PT(hard) > 5 GeV/c!

1% of “Min-Bias” events have PT(hard) > 10 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)!

Lots of “hard” scattering in “Min-Bias” at the Tevatron!

Ten decades!

pT = 50 GeV/c!



LHC MB Predictions: 900 GeVLHC MB Predictions: 900 GeV

Proton Proton


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/d for the region || < 0.6.

Proton Proton


Charged Particle Density: dN/d

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PseudoRapidity

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ALICE INEL

UA5 INEL

pyDW INEL (2.67)

pyS320 INEL (2.70)

RDF Preliminary

INEL = HC+DD+SD 900 GeV

Charged Particles (all pT)


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PseudoRapidity

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UA5

ALICE

pyDW_10mm (3.04)

pyS320_10mm (3.09)

NSD = HC+DD 900 GeV

RDF Preliminary


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ALICE INELUA5 INELpyDW times 1.11 (2.97)pyS320 times 1.11 (3.00)

RDF Preliminary

INEL = HC+DD+SD 900 GeV

times 1.11

Charged Particles (all pT)

Off by 11%!



ATLAS INEL dN/dATLAS INEL dN/d

Soft particles!

None of the tunes fit the ATLAS INEL dN/d data with PT > 100 MeV! They all predict too few particles.

The ATLAS Tune AMBT1 was designed to fit the inelastic data for Nchg ≥ 6 with pT > 0.5 GeV/c!

Off by 20-50%!



PYTHIA Tune DWPYTHIA Tune DWCharged Particle Density: dN/d

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RDF PreliminaryALICE INEL data


pT > 0.5 GeV/c

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At Least 1 Charged Particle || < 0.8

ALICE inelastic data at 900 GeV on the dN/d distribution for charged particles (pT > PTmin) for events with at least one charged particle with pT > PTmin and || < 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.

If one increases the pT the agreement

improves!

Tune DW

Proton Proton


The same thing occurs at 7 TeV! ALICE, ATLAS, and CMS data coming soon.




ALICE inelastic data at 900 GeV on the dN/d distribution for charged particles (pT > PTmin) for events with at least one charged particle with pT > PTmin and || < 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).


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Diffraction contributes less at

harder scales!

Tune DW

Proton Proton


Cannot trust PYTHIA 6.2 modeling of diffraction!




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CMS dN/dCMS dN/d

Generator level dN/d (all pT). Shows the NSD = HC + DD and the HC = ND contributions for Tune DW. Also shows the CMS NSD data.

CMS

Tune DW

All pT

Soft particles!

Proton Proton


Off by 50%!

Okay if the Monte-Carlo does not fitthe data what do we do?

We tune the Monte-Carloto fit the data!

Be careful not to tune away new physics!



PYTHIA Tune Z1PYTHIA Tune Z1

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton




I believe that it is time to move to PYTHIA 6.4 (pT-ordered parton showers and new MPI model)!

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.

UE&MB@CMSUE&MB@CMS

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)

Color

Connections

PARP(82)

Diffraction

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!



PYTHIA Tune Z1PYTHIA Tune Z1Parameter

Tune Z1

(R. Field CMS)Tune AMBT1

(ATLAS)

Parton Distribution Function CTEQ5L LO*

PARP(82) – MPI Cut-off 1.932 2.292

PARP(89) – Reference energy, E0 1800.0 1800.0

PARP(90) – MPI Energy Extrapolation 0.275 0.25

PARP(77) – CR Suppression 1.016 1.016

PARP(78) – CR Strength 0.538 0.538

PARP(80) – Probability colored parton from BBR 0.1 0.1

PARP(83) – Matter fraction in core 0.356 0.356

PARP(84) – Core of matter overlap 0.651 0.651

PARP(62) – ISR Cut-off 1.025 1.025

PARP(93) – primordial kT-max 10.0 10.0

MSTP(81) – MPI, ISR, FSR, BBR model 21 21

MSTP(82) – Double gaussion matter distribution 4 4

MSTP(91) – Gaussian primordial kT 1 1

MSTP(95) – strategy for color reconnection 6 6

Parameters not shown are the PYTHIA 6.4

defaults!




CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dd, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and || < 2.0. The data are uncorrected and compared with PYTHIA Tune Z1 after detector simulation (SIM).

CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dd, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and || < 2.0. The data are uncorrected and compared with PYTHIA Tune DW and D6T after detector simulation (SIM).


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7 TeV

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D6T


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7 TeV

Tune Z1 (CTEQ5L)PARP(82) = 1.932PARP(90) = 0.275PARP(77) = 1.016PARP(78) = 0.538

Tune Z1 is a PYTHIA 6.4 using pT-ordered parton showers and

the new MPI model!

Color reconnection suppression.Color reconnection strength.

CMS CMSTune Z1




CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and || < 2.0. The data are uncorrected and compared with PYTHIA Tune Z1 after detector simulation (SIM).

CMS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c and || < 2.0. The data are uncorrected and compared with PYTHIA Tune DW and D6T after detector simulation (SIM).


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Tune Z1 (CTEQ5L)PARP(82) = 1.932PARP(90) = 0.275PARP(77) = 1.016PARP(78) = 0.538

Tune Z1 is a PYTHIA 6.4 using pT-ordered parton showers and

the new MPI model!

Color reconnection suppression.Color reconnection strength.

CMS CMSTune Z1




ALICE preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected and compared with PYTHIA Tune Z1 at the generrator level.

ALICE preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected and compared with PYTHIA Tune Z1 at the generator level.

ALICE UE Data: Talk by S. ValleroMPI@LHC 2010 Glasgow, Scotland

November 30, 2010


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ALICE corrected dataTune Z1 generator level


900 GeV

7 TeV


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sum

Den

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(G

eV/c

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RDF PreliminaryALICE corrected data

Tune Z1 generator level


900 GeV

7 TeV

ALICETune Z1

ALICETune Z1





ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 2.5. The data are corrected and compared with PYTHIA Tune Z1 at the generrator level.

ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle density, dN/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 2.5. The data are corrected and compared with PYTHIA Tune Z1 at the generator level.

ATLAS Note: ATLAS-CONF-2010-029May 29, 2010


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ATLAS corrected dataTune Z1 generator level

900 GeV

7 TeV



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PT

sum

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7 TeV


ATLASATLASTune Z1Tune Z1





ATLAS preliminary data at 7 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 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 || < 2.5.

ATLAS preliminary data at 7 TeV on the “transverse” charged particle density, dN/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 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 || < 2.5.


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"Tra

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7 TeV

Charged Particles (||<2.5)

PT > 0.1 GeV/c

PT > 0.5 GeV/c


0.0

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"Tra

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7 TeV

PT > 0.1 GeV/c

PT > 0.5 GeV/cCharged Particles (||<2.5) Tune Z1

ATLASTune Z1

ATLAS

Factor of 2 increase!

"Transverse" Ratio: PT > 0.1 and > 0.5 GeV/c

0.0

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/0.5

RDF Preliminary generator levelTune Z1 (solid)

Tune DW (dashed)

7 TeVCharged Particles (||<2.5)

Charge Particle Density

Charge PTsum Density

Rick FieldMPI@LHC 2010 Glasgow, Scotland

December 2, 2010




ATLAS preliminary data at 7 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and pT > 0.1 GeV/c (|| < 2.5). The data are corrected and compared with PYTHIA Tune Z1 at the generator level.

ATLAS preliminary data at 7 TeV on the “transverse” charged particle density, dN/dd, as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and pT > 0.1 GeV/c (|| < 2.5). The data are corrected and compared with PYTHIA Tune Z1 at the generator level.


0.0

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7 TeV


PT > 0.1 GeV/c

PT > 0.5 GeV/c


0.0

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PTmax (GeV/c)

"Tra

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7 TeV

PT > 0.1 GeV/c

PT > 0.5 GeV/cCharged Particles (||<2.5)


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7 TeV

PT > 0.1 GeV/c

PT > 0.5 GeV/cCharged Particles (||<2.5)

Tune Z1 ATLAS


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PT

su

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7 TeV

PT > 0.1 GeV/c

PT > 0.5 GeV/c


Tune Z1

ATLAS

ATLAS publication – arXiv:1012.0791December 3, 2010


"Transverse" Ratio: PT > 0.1 and > 0.5 GeV/c

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7 TeVCharged Particles (||<2.5)


Tune Z1 generator levelCharge Particle Density

Charge PTsum Density




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, || < 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).


1.0E-07

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Pro

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Theory + SIM

Normalized to 1



900 GeV 7 TeV

D6T

DW


1.0E-07

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1.0E+00

0 5 10 15 20 25 30 35 40


Pro

bab

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pyZ1 + SIM

Normalized to 1



900 GeV 7 TeV

Tune Z1

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, || < 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).

CMSCMS


of-mass energies!

Difficult to produce enough events with large “transverse” multiplicity at low

hard scale!



““Transverse” PTsum DistributionTransverse” PTsum Distribution

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, || < 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).

"Transverse" Charged PTsum Distribution

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

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0 5 10 15 20 25 30 35 40 45 50

PTsum (GeV/c)

Pro

bab

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Theory + SIM

Normalized to 1


900 GeV

7 TeV

D6T

DW


1.0E-06

1.0E-05

1.0E-04

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1.0E+00

0 5 10 15 20 25 30 35 40 45 50

PTsum (GeV/c)

Pro

bab

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pyZ1+ SIM

Normalized to 1


900 GeV

7 TeV

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, || < 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).

Tune Z1

CMSCMS


of-mass energies!

Difficult to produce enough events with large “transverse”

PTsum 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, || < 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).


1.0E-07

1.0E-06

1.0E-05

1.0E-04

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Theory + SIM

Normalized to 1


7 TeV



D6T

DW


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7 TeV



CMS uncorrected data at 7 TeV on the charged particle multiplicity distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 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).

Tune Z1CMS

CMS


hard scales!


hard scale!



““Transverse” PTsum DistributionTransverse” PTsum Distribution

CMS uncorrected data at 7 TeV on the charged PTsum distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 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).


1.0E-06

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PTsum (GeV/c)

Pro

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Theory + SIM

Normalized to 1



7 TeV

D6T

DW


1.0E-06

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PTsum (GeV/c)

Pro

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pyZ1 + SIM

Normalized to 1



7 TeV

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, || < 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).

CMSCMS


hard scales!

Difficult to produce enough events with large “transverse”

PTsum at low hard scale!



CMS dN/dCMS dN/dCharged Particle Density: dN/d

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pyZ1 HC (6.51)

pyZ1 NSD (5.58)

RDF Preliminary

7 TeV


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CMS NSD 7 TeV

pyX2 NSD (5.91)

pyZ1 NSD (5.58)CMS NSD all pT

RDF Preliminary

7 TeV

Generator level dN/d (all pT). Shows the NSD = HC + DD and the HC = ND contributions for Tune Z1. Also shows the CMS NSD data.

Generator level dN/d (all pT). Shows the NSD = HC + DD prediction for Tune Z1 and Tune X2. Also shows the CMS NSD data.

CMSCMS

Tune Z1

Proton Proton


Okay not perfect, but remember we do not know if the DD is correct!




ALICE inelastic data at 900 GeV on the dN/d distribution for charged particles (pT > PTmin) for events with at least one charged particle with pT > PTmin and || < 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.


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pT > 0.15 GeV/c


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pT > 0.5 GeV/c

pT > 1.0 GeV/c


Proton Proton

“Minumum Bias” Collisions

Okay not perfect, but remember we do not know if the SD & DD are correct!



NSD Multiplicity DistributionNSD Multiplicity Distribution

Generator level charged multiplicity distribution (all pT, || < 2) at 900 GeV and 7 TeV. Shows the NSD = HC + DD prediction for Tune Z1. Also shows the CMS NSD data.


1.0E-04

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Pro

ba

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Charged Particles (all PT, ||<2.0)

RDF Preliminarydata CMS NSD


7 TeV

900 GeV

CMS

Tune Z1

Difficult to produce enough events with large multiplicity!

Proton Proton

“Minumum Bias” Collisions

Okay not perfect!But not that bad!



MB & UEMB & UE

Generator level charged multiplicity distribution (all pT, || < 2) at 900 GeV and 7 TeV. Shows the NSD = HC + DD prediction for Tune Z1. Also shows the CMS NSD data.


1.0E-04

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Charged Particles (all PT, ||<2.0)

RDF Preliminarydata CMS NSD


7 TeV

900 GeV


1.0E-07

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pyZ1 + SIM

Normalized to 1



900 GeV 7 TeV

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, || < 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 CMSTune Z1

Tune Z1

“Min-Bias”


Difficult to produce enough events with large multiplicity!


hard scale!



MB & UEMB & UE

CMS uncorrected data at 7 TeV on the charged particle multiplicity distribution in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 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, || < 2) compared with Tune Z1 at the generator.

CMS

Tune Z1

Charged Particle Multiplicity

1.0E-05

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CMS PreliminaryTune Z1

Normalized to 1


7 TeV

Underlying Event"Transverse" Region

pT > 0.5 GeV/cPT(chgjet#1) > 20 GeV/c

Min-BiasNSD All pT

Amazing what we are asking the Monte-Carlo models to fit!

Charged Particle Multiplicity

1.0E-05

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CMS PreliminaryTune Z1

Normalized to 1


7 TeV

Underlying Event"Transverse" Region

pT > 0.5 GeV/cPT(chgjet#1) > 20 GeV/c

Min-BiasNSD All pT



Strange Particle ProductionStrange Particle Production

A lot more strange mesons at large pT than predicted by the Monte-Carlo Models!

K/ ratio fairly independent of the center-of-mass energy.

ALICE preliminarystat. error only

PhojetPythia ATLAS-CSCPythia D6TPythia Perugia-0

Factor of 2!



Min-Bias SummaryMin-Bias Summary

We need a better understanding and modeling of diffraction!

We are a long way from having a Monte-Carlo model that will fit all the features of the LHC min-bias data! There are more soft particles that expected!

PARP(90)

Color

Connections

PARP(82)

Diffraction

It is difficult for the Monte-Carlo models to produce a soft event (i.e. no large hard scale) with a large multiplicity. There seems to be more “min-bias” high multiplicity soft events at 7 TeV than predicted by the models!

The models do not produce enough strange particles! I have no idea what is going on here! The Monte-Carlo models are constrained by LEP data.



The LHC in 2011The LHC in 2011 Beam back around 21st February.

2 weeks re-commissioning with beam (at least).

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).

Peak luminosity 6.4 x 1032

Integrated per day 11 pb-1

200 days 2.2 fb-1

Stored energy 72 MJ

Beam back around on February 21st!

This is fun!

Documents

LHC First Data