Early LHC Measurements

UE&MB Working Group Meeting LPCC May 31, 2010

Rick Field – Florida/CDF/CMS

Early LHC MeasurementsEarly LHC Measurements

Rick FieldUniversity of Florida

Outline of Talk

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation “Min-bias” Summary.

UE Summary.

LHC “min-bias” data at 7 TeV.

UE&MB@CMSUE&MB@CMS

MC Tunes: What have we learned?

The new ATLAS & CMS “underlying event” results.

PARP(90)

Color

Connections

PARP(82)

Diffraction



ATLAS & CMS UE AnalysesATLAS & CMS UE Analyses

Uncorrected data on the “transverse” region as defined by the leading track, PTmax, and the leading charged particle jet, PT(chgjet#1) at 900 GeV (pT > 0.5 GeV/c, || < 2.0) compared with several QCD Monte-Carlo models after detector simulation.

Corrected data on the “towards”, “away”, and “transverse” regions as defined by the leading track, PTmax, at 7 TeV and 900 GeV (pT > 0.5 GeV/c, || < 2.5) compared with several QCD Monte-Carlo models at the generator level.

UE&MB@CMSUE&MB@CMS



ATLAS & CMS UE AnalysesATLAS & CMS UE Analyses

Uncorrected data on the “transverse” region as defined by the leading track, PTmax, and the leading charged particle jet, PT(chgjet#1) at 900 GeV (pT > 0.5 GeV/c, || < 2.0) compared with several QCD Monte-Carlo models after detector simulation.

Corrected data on the “towards”, “away”, and “transverse” regions as defined by the leading track, PTmax, at 7 TeV and 900 GeV (pT > 0.5 GeV/c, || < 2.5) compared with several QCD Monte-Carlo models at the generator level.

UE&MB@CMSUE&MB@CMS

Please note that I have read the ATLAS and CMS data pointsoff these papers with a ruler

so that I can plot the dataand make comparisons!

Please refer to these papers(not my plots) for the

true data points!

None of my plots are the original figures from the papers!



““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).

"Transverse" Charged Particle Density: dN/dd

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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



““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

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ChgJet#1

PTmax




““Transverse” Charged PTsum DensityTransverse” Charged PTsum Density

"Transverse" Charged PTsum Density: dPT/dd

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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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sum

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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).



PYTHIA Tune CWPYTHIA Tune CW

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 CW after detector simulation.


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data uncorrectedpyCW + SIM

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CMS Preliminarydata uncorrected

pyCW + SIM

900 GeV


ChgJet#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 CW after detector simulation.

Tune DW → Tune CWPARP(82) = 1.9 → 1.8

PARP(90) = 0.25 → 0.30PARP(85) = 1.0 → 0.9

PARP(86) = 1.0 → 0.95



““Transverse” Charge DensityTransverse” Charge Density

PTmax Direction

“Toward”

“Transverse” “Transverse”

“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




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data corrected

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PTmax Direction

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PTmax Direction

“Toward”


“Away”

LHC 900 GeV

LHC7 TeV


ATLAS preliminary data on the charged particle density in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 900 GeV and 7 TeV as defined by PTmax.

factor of 2!

~0.4 → ~0.8




PTmax Direction

“Toward”


“Away”

PTmax Direction

“Toward”


“Away”

LHC 900 GeV

LHC7 TeV


Ratio of the ATLAS preliminary data on the charged particle density in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 900 GeV and 7 TeV as defined by PTmax compared with PYTHIA Tune CW, DW, and ATLAS MC08.

~0.4 → ~0.8

PARP(90) = 0.16

PARP(90) = 0.25

PARP(90) = 0.30


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RDF PreliminaryATLAS corrected datagenerator level theory

7 TeV / 900 GeV

Tune DWATLAS MC08

Tune CW



PYTHIA Tune DWPYTHIA Tune DW

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 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 DW at the generator level.


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ATLAS corrected dataTune DW generator level

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RDF PreliminaryATLAS corrected data

Tune DW generator level

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Tuning the Color ConnectionsTuning the Color Connections

Shows the charged particle and PTsum density in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 7 TeV as defined by the leading charged particle, PTmax, for pyX18GG8, pyX18GG1, and pyX18QQ at the particle level (i.e. generator level).

PTmax Direction

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“Away”


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ATLAS corrected datagenerator level theory

7 TeVCharged Particles (||<2.5, PT>0.5 GeV/c)

X18GG8

X18GG1X18QQ


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RDF PreliminaryATLAS corrected datagenerator level theory


X18GG8 X18GG1

X18QQ

Percent of ND = HC Cross-Section

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Tune A TuneDW,D6T

Tune X1 Tune X2 Tune X1844 ATLAS

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Shows the charged particle average pT in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 7 TeV as defined by the leading charged particle, PTmax, for pyX18GG8, pyX18GG1, and pyX18QQ at the particle level (i.e. generator level).

PTmax Direction

“Toward”


“Away”

"Transverse" Charged Average pT

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RDF Preliminarygenerator level theory


X18GG8

X18GG1

X18QQ

Tune A has 90% GG8 and Tune DW and D6T have100% GG8 in order to fit

the <pT> and PTsum/Nchgat the Tevatron!

"Transverse" Average PT

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data correctedgenerator level theory

"Leading Jet"MidPoint R=0.7 |(jet#1)|<2


PY Tune A

HW


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Tune A TuneDW,D6T


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GG8 has larger <pT>!




Shows the charged particle average pT in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 7 TeV as defined by the leading charged particle, PTmax, for pyX18GG8, pyX18GG1, and pyX18QQ at the particle level (i.e. generator level).

PTmax Direction

“Toward”


“Away”

"Transverse" Charged Average pT

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RDF Preliminarygenerator level theory


X18GG8

X18GG1

X18QQ

Tune A has 90% GG8 and Tune DW and D6T have100% GG8 in order to fit

the <pT> and PTsum/Nchgat the Tevatron!

"Transverse" Average PT

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data correctedgenerator level theory

"Leading Jet"MidPoint R=0.7 |(jet#1)|<2


PY Tune A

HW


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Tune A TuneDW,D6T


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GG8 has larger <pT>!

"Toward" Average PT Charged

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PT(Z-Boson) (GeV/c)

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CDF Run 2 Preliminarydata corrected

generator level theory

"Drell-Yan Production"70 < M(pair) < 110 GeV

Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair

HWJIM

ATLAS

pyAWpyDW




Shows the charged particle ratio PTsum/Nchg in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 7 TeV as defined by the leading charged particle, PTmax, for pyX18GG8, pyX18GG1, and pyX18QQ at the particle level (i.e. generator level).

PTmax Direction

“Toward”


“Away”

GG8 has larger PTsum/Nchg!"Transverse" Charged Particle Ratio: PTsum/Nchg

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PTmax (GeV/c)

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7 TeV


X18GG8

X18GG1

X18QQ


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Tune A TuneDW,D6T


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PYTHIA Tune X1PYTHIA Tune X1

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 X1 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 X1 at the generator level.


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ATLAS corrected dataTune X1 generator level

900 GeV

7 TeV



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Tune X1 generator level

900 GeV

7 TeV


Tune X1 → Tune CWPARP(82) = 1.9 → 1.8PARP(85) = 1.0 → 0.8PARP(86) = 1.0 → 0.9




Ratio of the ATLAS preliminary data on the charged PTsum density in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 900 GeV and 7 TeV as defined by PTmax compared with PYTHIA Tune X1 at the generator level.

Ratio of the ATLAS preliminary data on the charged particle density in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 900 GeV and 7 TeV as defined by PTmax compared with PYTHIA Tune X1 at the generator level.



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Charged Particles (||<2.5, PT>0.5 GeV/c) 7 TeV / 900 GeV




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Ratio of the ATLAS preliminary data on the charged PTsum density in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 900 GeV and 7 TeV as defined by PTmax compared with PYTHIA Tune X1 at the generator level.

Ratio of the ATLAS preliminary data on the charged particle density in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 2.5) at 900 GeV and 7 TeV as defined by PTmax compared with PYTHIA Tune X1 at the generator level.



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"Transverse" Charged Particle Ratio: PTsum/Nchg

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Charged Particles (||<2.5, PT>0.5 GeV/c) 7 TeV





Shows the data on the dependence of the “associated” charged particle density, dNchg/dd, for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” events with PTmax > 0.5 GeV/c and PTmax > 2.0 GeV/c compared with PYTHIA Tune A (after CDFSIM).

PTmax Direction

Correlations in

Associated Particle Density: dN/dd

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PY Tune A

CDF Preliminarydata uncorrectedtheory + CDFSIM

PTmaxPTmax not included (||<1.0, PT>0.5 GeV/c)

PY Tune A 1.96 TeV

PYTHIA Tune A predicts a larger correlation than is seen in the “min-bias” data (i.e. Tune A “min-bias” is a bit too “jetty”).

PTmax > 2.0 GeV/c

PTmax > 0.5 GeV/c

PTmax Direction

“Toward”


“Away”

Transverse Region Transverse

Region

PY Tune A

CDF Run 2 Min-Bias “Associated”CDF Run 2 Min-Bias “Associated”Charged Particle DensityCharged Particle Density



Shows the data on the dependence of the “associated” charged particle density, dNchg/dd, for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) relative to PTmax (rotated to 180o) for “min-bias” events with PTmax > 0.5 GeV/c and PTmax > 2.0 GeV/c compared with PYTHIA Tune A (after CDFSIM).

PTmax Direction

Correlations in

Associated Particle Density: dN/dd

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PTmax > 0.5 GeV/c

PY Tune A

CDF Preliminarydata uncorrectedtheory + CDFSIM

PTmaxPTmax not included (||<1.0, PT>0.5 GeV/c)

PY Tune A 1.96 TeV

PYTHIA Tune A predicts a larger correlation than is seen in the “min-bias” data (i.e. Tune A “min-bias” is a bit too “jetty”).

PTmax > 2.0 GeV/c

PTmax > 0.5 GeV/c

PTmax Direction

“Toward”


“Away”

Transverse Region Transverse

Region

PY Tune A

CDF Run 2 Min-Bias “Associated”CDF Run 2 Min-Bias “Associated”Charged Particle DensityCharged Particle Density

The problem in fitting the “toward”associated particle density seen

10 years ago at CDF also appearsat 900 GeV and 7 TeV inthe ATLAS & CMS data!



UE SummaryUE SummaryThe “underlying event” at 7 TeV

and 900 GeV is almost what we expected! I expect that a PYTHIA 6 tune just slightly different than Tune DW will fit the UE data perfectly including the energy dependence (Tune X1 is not bad!). I also expect to see good PYTHIA 8 tune soon!

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

I will quickly show you some of my attempts (all failures) to fit the LHC “min-bias” data.

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

PARP(90)

Color

Connections

PARP(82)

Diffraction



<PT> versus Nchg<PT> versus Nchg

Shows how changing the color connections affects the <pT> versus Nchg . Here the data and theory are non-diffractive (ND). Here you can understand why Tune DW rises faster than the data and why the ATLAS tunes does so poorly.

Average PT versus Nchg

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ND 1.96 TeV

ATLAS

pyDW pyA


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pyX18GG8 Run2

pyX18GG1 Run2

pyX18QQ Run2




ND 1.96 TeV

The CDF “min-bias” data aretelling us that the correct tune

must be largely GG8!Okay Tune A and DW have

a little to much GG8!

CDF ND data on the <pT> versus Nchg compared with Tune A(ND), Tune DW(ND) and Tune ATLAS MC08(ND). This is why no one likes the ATLAS MC08 Tune!


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<PT> versus Nchg<PT> versus Nchg

Shows how changing the color connections affects the <pT> versus Nchg . Here the data and theory are non-diffractive (ND). Here you can understand why Tune DW rises faster than the data and why the ATLAS tunes does so poorly.


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pyDW pyA


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pyX18GG8 Run2

pyX18GG1 Run2

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ND 1.96 TeV

The CDF “min-bias” data aretelling us that the correct tune

must be largely GG8!Okay Tune A and DW have

a little to much GG8!

CDF ND data on the <pT> versus Nchg compared with Tune A(ND), Tune DW(ND) and Tune ATLAS MC08(ND). This is why no one likes the ATLAS MC08 Tune!


90%100%

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Tune A TuneDW,D6T


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CDF Published Data

pyX188090




ND 1.96 TeV

80% GG810% GG110% QQ

Tune X1!




Tune X2 uses the PYTHIA HC, SD, DD fractions for INEL (above left) and HC, DD fractions for NSD (above right). PYTHIA is thought to predict to much SD and DD. Tune X3 (not ready yet) will use the ALICE DD and SD fractions (see above). For now I will try and do the best possible using the PYTHIA SD and DD fractions.

For Tune X2 I will attempt to produce enough charged particles (all pT) at 7 TeV (i.e. fit the CMS NSD dN/d distribution). It is important to have a tune that gets the average multiplicity right! I will only look at 7 TeV “min-bias” data. Tune X2 does fit the “underlying event” data!

Percent of INEL Cross-Section

66.5%76.7%

67.9%78.3%

22.3%15.3%

19.2%13.2%

11.2% 8.0% 12.9% 9.2%

0%

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100%

PY 900 ALICE 900 PY 7 TEV Tune X3 7 TeV

Pe

rce

nt

INE

L

DD

SD

HC

Percent of NSD Cross-Section

85.6% 90.6%84.1% 89.0%

14.4% 9.4%15.9% 10.4%

0%

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PY 900 ALICE 900 PY 7 TEV Tune X3 7 TeV

Pe

rce

nt

NS

D

DD

HC



Color ConnectionsColor ConnectionsAverage Number of Charged Particles

66.4

93.2

79.9

14.1 17.0

68.3

98.8

83.9

14.1 17.0

70.3

104.8

88.4

14.1 17.0

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PARP(82)=1.8

PARP(82)=1.7

PARP(82)=1.6

All pT All 7 TeV Average Number of Charged Particles

20.5

34.0

27.7

3.0 3.0

21.2

36.4

29.4

3.0 3.0

21.9

39.1

31.3

3.0 3.0

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GG8 GG1 QQbar SD DD

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PARP(82)=1.8

PARP(82)=1.7

PARP(82)=1.6

All pT ||<2

7 TeV

Shows how changing the color connections affects the average number of charged particles. Also shows the SD and ND contributions. CMS sees about ~24 charged particles (all pT, || < 2). Percent of ND = HC Cross-Section

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Tune A TuneDW,D6T


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CMS



Color ConnectionsColor Connections

Generator level dN/d (all pT). Shows the HC contribution for the three color connections GG8, GG1, and QQbar. Also shows the CMS NSD data.

Charged Particle Density: dN/d

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-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0

PseudoRapidity

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CMS NSD 7 TeV

pyX18GG1 HC (8.2)

pyX18QQ HC (6.7)

pyX18GG8 HC (4.9)

7 TeV

Charged Particles (all PT)

RDF Preliminarydata CMS NSD


DW, DWT, and D6T are 100% GG8!

pyATLAS is equal mixtures of all three!


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Tune A TuneDW,D6T


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GG8




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


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CMS NSD 7 TeV

pyX2 HC (6.87)

pyX2 NSD (5.91)

pyDD (0.7)

7 TeV

Charged Particles (all PT)

RDF Preliminarydata CMS NSD

generator level theory60% GG140% GG8

84% HC16% DD




Shows the CMS NSD data for dN/d (all pT) and the ATLAS INEL data for dN/d (pT > 0.5 GeV/c, Nchg ≥ 1) compared with Tune X2 (generator level).


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RDF Preliminary

Tune X2 7 TeV

CMS NSD all pT

ATLAS INEL pT > 0.5 GeV/c Nchg ≥ 1

SD = 9.4%, DD = 6.8%!



Color ConnectionsColor ConnectionsAverage Charged Particle PT

0.53

0.44

0.48

0.33 0.34

0.54

0.44

0.48

0.33 0.34

0.54

0.43

0.48

0.33 0.34

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0.70

GG8 GG1 QQbar SD DD

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erag

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T (

GeV

/c)

PARP(82)=1.8

PARP(82)=1.7

PARP(82)=1.6

All pT All 7 TeV Average Charged Particle PT

0.62

0.47

0.53

0.36 0.36

0.63

0.47

0.52

0.36 0.36

0.64

0.46

0.52

0.36 0.36

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0.60

0.70

GG8 GG1 QQbar SD DD

Av

erag

e P

T (

GeV

/c)

PARP(82)=1.8

PARP(82)=1.7

PARP(82)=1.6

All pT || < 2

7 TeV

Tune X2 gives the right average number of charged particles but <pT> = 0.501

is a long way off on the the observed average pT (i.e. too small)!

Shows how changing the color connections affects the average transverse momentum of charged particles. Also shows the SD and ND contributions. CMS sees <pT> ~ 0.545 GeV/c (all pT, || < 2).

CMS




Shows the CMS NSD data for <pT> versus Nchg (all pT) and the ATLAS INEL data for <pT> versus Nchg (pT > 0.5 GeV/c, Nchg ≥ 1) compared with Tune X2 (generator level).


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RDF PreliminaryATLAS INEL data


Tune X2




Shows the ATLAS INEL data for <pT> versus Nchg (pT > 0.5 GeV/c, Nchg ≥ 1) compared with Tune X18GG8, X18GG1, and X18QQ (left) and PYTHIA Tune X1844 (INEL, right).


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pyX18GG8

pyX18GG1

pyX18QQ


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Tune X1844


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Tune A TuneDW,D6T


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GG8

Gives the right <pT>!




Shows the ATLAS INEL data for <pT> versus Nchg (pT > 0.5 GeV/c, Nchg ≥ 1) compared with Tune X18GG8, X18GG1, and X18QQ (left) and PYTHIA Tune X1844 (INEL, right).


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pyX18GG8

pyX18GG1

pyX18QQ


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Tune X1844


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Tune A TuneDW,D6T


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PseudoRapidity

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CMS Preliminary

7 TeV NSD All pT

CMS NSD all pTTune X2

Tune X1844



Min-Bias SummaryMin-Bias Summary

I think the problem is that we do not understand diffraction well enough yet!

We are a long way from having a model that will fit all the features of the LHC min-bias data!

We are learning a lot about how nature works!

PARP(90)

Color

Connections

PARP(82)

Diffraction

Early LHC Measurements

Documents

Transcript of Early LHC Measurements