PIC 2011, Vancouver August 29, 2011 Rick Field – Florida/CDF/CMSPage 1 Physics in Collision Rick Field University of Florida Outline Examine

PIC 2011, Vancouver August 29, 2011

Rick Field – Florida/CDF/CMS Page 1

Physics in CollisionPhysics in Collision

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

Rick FieldUniversity of Florida

UE&MB@CMSUE&MB@CMS

Outline

Examine the connection between the “underlying event” in a hard scattering process (UE) and “min-bias” collisions (MB).

ATLAS

How well can we predict “min-bias” collisions at the LHC?

Strange particle and baryon production at the LHC.

How well did we do at predicting the behavior of the “underlying event” at the LHC (900 GeV and 7 TeV)?

Min-Bias and the Underlying Event at the LHC

CMS

How universal are the QCD Monte-Carlo model tunes?

Proton Proton

“Minimum Bias” Collisions

K+

u s K-

u s

Kshort

d s s d +

p

u u d

u d s

d s s



Jet #1 Direction

“Toward”

“Transverse” “Transverse”

“Away”

“Leading Jet”

““Towards”, “Away”, “Transverse”Towards”, “Away”, “Transverse”

CDF data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level).

Charged Particle Density: dN/dd

0

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PT(jet#1) (GeV/c)

Ave

rage

Cha

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CDF Run 2 Preliminarydata corrected

pyA generator level

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

Charged Particles (||<1.0, PT>0.5 GeV/c)

"Away"

"Toward"

"Transverse"

CDF data at 1.96 TeV on the charged particle scalar pT sum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “leading jet” events as a function of the leading jet pT for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level (with errors that include both the statistical error and the systematic uncertainty) and are compared with PYTHIA Tune A at the particle level (i.e. generator level).

Factor of ~4.5

Charged PTsum Density: dPT/dd

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pyA generator level



"Toward""Away"

"Transverse"Factor of ~16



Z-Boson Direction

“Toward”


“Away”

Charged Particle DensityCharged Particle Density

CDF data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson” and “Leading Jet” events as a function of the leading jet pT or PT(Z) for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level and are compared with PYTHIA Tune AW and Tune A, respectively, at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”


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PT(jet#1) (GeV/c)

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pyA generator level



"Away"

"Toward"

"Transverse"


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PT(Z-Boson) (GeV/c)

Ave

rage

Cha

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pyAW generator level"Away"

"Transverse"

"Toward"

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

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

Proton AntiProton

High PT Z-Boson Production

Z-boson

Outgoing Parton


Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton




"Transverse" Charged Particle Density: dN/dd

0.0

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generator level theory


"Leading Jet"

"Z-Boson"

"Away" Charged Particle Density: dN/dd

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"Aw

ay"

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"Leading Jet"

"Z-Boson"



Z-Boson Direction

“Toward”


“Away”

Charged Particle DensityCharged Particle Density

CDF data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with PYTHIA Tune DW.

Z-Boson Direction

“Toward”


“Away”

Proton Proton


Z-boson

Outgoing Parton



0

1

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3

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PT(lepton-pair) GeV/c

Ave

rage

Cha

rged

Den

sity

CMS Preliminarydata corrected

pyDW generator level


"Away"

"Transverse"

"Toward"

Drell-Yan Production60 < M(pair) < 120 GeV

7 TeV

Proton AntiProton


Z-boson

Outgoing Parton



0

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3

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Ave

rage

Cha

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Den

sity

CDF Run 2data corrected



"Away"

"Transverse"

"Toward"


1.96 TeV

CMS data at 7 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 2 for Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with PYTHIA Tune DW.

CDF: Proton-Antiproton Collisions at 1.96 GeVLepton Cuts: pT > 20 GeV || < 1.0

Mass Cut: 70 < M(lepton-pair) < 110 GeVCharged Particles: pT > 0.5 GeV/c || < 1.0

CMS: Proton-Proton Collisions at 7 GeVLepton Cuts: pT > 20 GeV || < 2.4

Mass Cut: 60 < M(lepton-pair) < 120 GeVCharged Particles: pT > 0.5 GeV/c || < 2.0

"Toward" Charged Particle Density: dN/dd

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Cha

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ticle

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Drell-Yan Production Charged Particles (PT>0.5 GeV/c)

CDF 1.96 TeV

CMS 7 TeV

RDF Preliminarydata corrected

pyDW generator levelCMS

Large increase in the UE in going from 1.96 TeV

to 7 TeV as predicted by PYTHIA Tune DW!



Z-Boson Direction

“Toward”


“Away”

Charged PTsum DensityCharged PTsum Density

CDF data at 1.96 TeV on the charged scalar PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for “Z-Boson” and “Leading Jet” events as a function of the leading jet pT or PT(Z) for the “toward”, “away”, and “transverse” regions. The data are corrected to the particle level and are compared with PYTHIA Tune AW and Tune A, respectively, at the particle level (i.e. generator level).

Jet #1 Direction

“Toward”


“Away”

Proton AntiProton


Z-boson

Outgoing Parton


Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton





0.1

1.0

10.0

0 20 40 60 80 100

PT(Z-Boson) (GeV/c)

Cha

rged

PTs

um D

ensi

ty (G

eV/c

) CDF Run 2 Preliminarydata corrected

pyAW generator level

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

"Away"

"Transverse"

"Toward"



0.1

1.0

10.0

100.0

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PT(jet#1) (GeV/c)

Cha

rged

PTs

um D

ensi

ty (G

eV/c

)


pyA generator level



"Toward"

"Away"

"Transverse"

"Transverse" Charged PTsum Density: dPT/dd

0.0

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1.0

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2.0

0 20 40 60 80 100 120 140 160 180 200


"Tra

nsve

rse"

PTs

um D

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eV/c

)




"Leading Jet"

"Z-Boson"

"Away" Charged PTsum Density: dPT/dd

0

5

10

15

20

0 20 40 60 80 100 120 140 160 180 200


"Aw

ay"

PTsu

m D

ensi

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eV/c

) CDF Run 2 Preliminarydata corrected



"Leading Jet"

"Z-Boson"



Z-Boson Direction

“Toward”


“Away”

Charged PTsum DensityCharged PTsum Density

Z-Boson Direction

“Toward”


“Away”

Proton Proton


Z-boson

Outgoing Parton


Proton AntiProton


Z-boson

Outgoing Parton



0.1

1.0

10.0

0 20 40 60 80 100


Cha

rged

PTs

um D

ensi

ty (G

eV/c

) CDF Run 2data corrected



"Away"

"Transverse"

"Toward"


1.96 TeV


0.1

1.0

10.0

0 20 40 60 80 100


Cha

rged

PTs

um D

ensi

ty (G

eV/c

) CMS Preliminarydata corrected



"Away"

"Transverse"

"Toward"


7 TeV

"Toward" Charged PTsum Density: dPT/dd

0.0

0.5

1.0

1.5

0 20 40 60 80 100


Cha

rged

PTs

um D

ensi

ty (G

eV/c

)


CDF 1.96 TeV

CMS 7 TeV



CDF data at 1.96 TeV on the charged PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with PYTHIA Tune DW.

CMS data at 7 TeV on the charged PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with PYTHIA Tune DW.

CMS

Large increase in the UE in going from 1.96 TeV

to 7 TeV as predicted by PYTHIA Tune DW!



PYTHIA Tune DWPYTHIA Tune DW

PTmax Direction

“Toward”


“Away”


0.0

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1.2

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PTmax (GeV/c)

"Tra

nsve

rse"

Cha

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Den

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.

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.


0.0

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Cha

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900 GeV

CMS Preliminarydata uncorrected

pyDW + SIM


7 TeV

CMS ATLAS

PT(chgjet#1) Direction

“Toward”


“Away”



PYTHIA Tune DWPYTHIA Tune DW

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.


0.0

0.4

0.8

1.2

1.6

0 5 10 15 20 25 30 35 40 45 50

PT(chgjet#1) (GeV/c)

Cha

rged

PTs

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eV/c

)

CMS Preliminarydata uncorrected

pyDW + SIM


900 GeV

7 TeV


0.0

0.5

1.0

1.5

0 2 4 6 8 10 12 14 16 18 20

PTmax (GeV/c)

PTs

um D

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eV/c

)

RDF PreliminaryATLAS corrected data

Tune DW generator level

900 GeV

7 TeV


CMS ATLAS

PTmax Direction

“Toward”


“Away”

PT(chgjet#1) Direction

“Toward”


“Away”

Overall PYTHIA Tune DW is in amazingly good agreement with the

Tevatron Jet production and Drell-Yan dataand did a very good job in predicting theLHC Jet production and Drell-Yan data!

(although not perfect)



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 UE DataCMS UE Data

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 corrected and compared with PYTHIA Tune Z1 at the generator level.

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 corrected and compared with PYTHIA Tune Z1 at the generator level.

CMS


0.0

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PT(chgjet#1) GeV/c

Cha

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Par

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Den

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Tune Z1 generator level

900 GeV

7 TeV



0.0

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PTsu

m D

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GeV

/c)




900 GeV

7 TeV

Tune Z1

Very nice agreement!CMS correcteddata!

CMS correcteddata!

CMSTune Z1



ATLAS UE DataATLAS UE Data

ATLAS published 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 published 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.

ATLASATLASTune Z1Tune Z1

ATLAS publication – arXiv:1012.0791December 3, 2010


0.0

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PTmax (GeV/c)

"Tra

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RDF Preliminary ATLAS corrected dataTune Z1 generator level

900 GeV

7 TeV


0.0

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1.5

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PTmax (GeV/c)

PTs

um D

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eV/c

)




900 GeV

7 TeV



CMS-ATLAS UE DataCMS-ATLAS UE Data

CMS preliminary data at 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 together with the ATLAS published 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.


0.0

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

Cha

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7 TeV Charged Particles (PT > 0.5 GeV/c)

CMS (red)ATLAS (blue)




0.0

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

Cha

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7 TeV Charged Particles (PT > 0.5 GeV/c)

CMS (red)ATLAS (blue)

Amazing agreement!

Tune Z1

CMS: Chgjet#1

ATLAS: PTmax Tune Z1



ALICE UE DataALICE UE Data

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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PTsu

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RDF PreliminaryALICE corrected data



900 GeV

7 TeV

ALICETune Z1

ALICETune Z1

I read the points off with a ruler!




CMS data at 900 GeV 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 corrected and compared with PYTHIA Tune Z1 at the generator level.


0.0

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900 GeV

7 TeV



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

Cha

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CDF 1.96 TeV

Charged Particles (PT>0.5 GeV/c)

CMS 7 TeV

CMS 900 GeV


pyZ1 generator level


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0 50 100 150 200 250 300


Cha

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CDF 1.96 TeV


CMS 7 TeV

CMS 900 GeV



Tune Z1

CDF data at 1.96 TeV on the “transverse” charged particle density, dN/dd, as defined by the leading calorimeter jet (jet#1) for charged particles with pT > 0.5 GeV/c and || < 1.0. The data are corrected and compared with PYTHIA Tune Z1 at the generator level.

Tune Z1




CDF data at 1.96 TeV on the “transverse” charged PTsum density, dPT/dd, as defined by the leading calorimeter jet (jet#1) for charged particles with pT > 0.5 GeV/c and || < 1.0. The data are corrected and compared with PYTHIA Tune Z1 at the generator level.

CMS 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 corrected and compared with PYTHIA Tune Z1 at the generator level.


0.0

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PTsu

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/c)




900 GeV

7 TeV


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CDF 1.96 TeV

CMS 7 TeV

CMS 900 GeV




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CMS 7 TeV

CMS 900 GeV



Tune Z1 Tune Z1



Z-Boson Direction

“Toward”


“Away”


Z-Boson Direction

“Toward”


“Away”

Proton Proton


Z-boson

Outgoing Parton


Proton AntiProton


Z-boson

Outgoing Parton



0

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Ave

rage

Cha

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Den

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"Away"

"Transverse"

"Toward"


7 TeV


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Ave

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Cha

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Den

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CDF Run 2data corrected



"Away"

"Transverse"

"Toward"


1.96 TeV

CDF data at 1.96 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 1 for Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with PYTHIA Tune Z1.

CMS data at 7 TeV on the density of charged particles, dN/dd, with pT > 0.5 GeV/c and || < 2 for Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with PYTHIA Tune Z1.

"Toward" Charged Particle Density: dN/dd

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Cha

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Den

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CDF 1.96 TeV

CMS 7 TeV



Tune Z1 describes the energy dependence fairly

well!

CMS



Z-Boson Direction

“Toward”


“Away”


Z-Boson Direction

“Toward”


“Away”

Proton Proton


Z-boson

Outgoing Parton


Proton AntiProton


Z-boson

Outgoing Parton


CDF data at 1.96 TeV on the charged PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 1 for Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with PYTHIA Tune Z1.

CMS data at 7 TeV on the charged PTsum density, dPT/dd, with pT > 0.5 GeV/c and || < 2 for Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with PYTHIA Tune Z1.


0.1

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Cha

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PTs

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eV/c

) CDF Run 2data corrected



"Away"

"Transverse"

"Toward"


1.96 TeV


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Cha

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PTs

um D

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eV/c




"Away"

"Transverse"

"Toward"


7 TeV

"Toward" Charged PTsum Density: dPT/dd

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CMS



PYTHIA Tune Z1PYTHIA Tune Z1"Transverse" Charged Particle Density: dN/dd

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data correctedpyZ1 generator level

"Away" Charged Particle Density: dN/dd

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7 TeV Chgjet Production

Drell-Yan Production

Tune Z1 Tune Z1

Tune Z1Tune Z1



PYTHIA Tune Z1PYTHIA Tune Z1"Transverse" Charged PTsum Density: dPT/dd

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"Away" Charged PTsum Density: dPT/dd

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7 TeV Chgjet Production

Drell-Yan Production

Tune Z1

Tune Z1

Tune Z1Tune Z1

Overall amazingly good agreementwith the LHC and Tevatron

Jet production and Drell-Yan!(although not perfect yet)

What about Min-Bias?



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 +

+ …

“Underlying Event”

“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)!



Min-Bias CollisionsMin-Bias Collisions

CMS NSD data on the charged particle rapidity distribution at 7 TeV compared with PYTHIA Tune Z1. The plot shows the average number of particles per NSD collision per unit , (1/NNSD) dN/d.

CMS

Proton Proton


Okay not perfect, but remember we know that SD and DD are not modeled well!

Charged Particle Density: dN/d

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CMS DataPYTHIA Tune Z1

NSD (all pT) 7 TeV

ALICE NSD data on the charged particle rapidity distribution at 900 GeV compared with PYTHIA Tune Z1. The plot shows the average number of particles per INEL collision per unit , (1/NINEL) dN/d.

Tune Z1


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ALICE DataPYTHIA Tune Z1

INEL (all pT) 900 GeV

Tune Z1

ALICE

NSD = ND + DD

INEL = NSD + SD



MB versus UEMB versus UE

CMS NSD data on the charged particle rapidity distribution at 7 TeV compared with PYTHIA Tune Z1. The plot shows the average number of charged particles per NSD collision per unit , (1/NNSD) dN/d.

CMS

Proton Proton



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NSD (all pT) 7 TeV

Tune Z1NSD = ND + DD

CMS NSD data on the charged particle rapidity distribution at 7 TeV compared with PYTHIA Tune Z1. The plot shows the average number of charged particles per NSD collision per unit , (1/NNSD) dN/dd.


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Divide be 2




Proton Proton


CMSTune Z1 NSD = ND + DD



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Transverse Charged Particle Density: dN/dd

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Charged Particles (|| < 2, all pT)

RDF PreliminaryPYTHIA Tune Z1

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton




Shows the density of charged particles in the “transverse” region as a function of PTmax for charged particles (All pT, || < 2) at 7 TeV from PYTHIA Tune Z1.

Tune Z1

Factor of 2!




Proton Proton


CMSTune Z1 NSD = ND + DD



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ATLAS data on the density of charged particles in the “transverse” region as a function of PTmax for charged particles (pT > 0.1 GeV/c, || < 2.5) at 7 TeV compared with PYTHIA Tune Z1.

Factor of 2!


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ATLAS



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.

Charged Multiplicity Distribution

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Number of Charged Particles

Prob

abili

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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!



"Transverse" Charged Particle Multiplicity

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CMS Preliminary Data Corrected



7 TeV

PT(chgjet#1) > 3 GeV/c

900 GeV

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.

Charged Multiplicity Distribution

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Prob

abili

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Charged Particles (all PT, ||<2.0)

RDF Preliminarydata CMS NSD


7 TeV

900 GeV

CMS corrected 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 generator level.

CMS

CMS

Tune Z1Tune Z1

“Min-Bias” “Underlying Event”

Difficult to produce enough events with large multiplicity!

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

hard scale!



How How UniversalUniversal are the Tunes? are the Tunes?

PARP(82)

Diffraction

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton




Do we need a separate tune for each center-of-mass energy? 900 GeV, 1.96 TeV, 7 TeV, etc.

PYTHIA Tune DW did a nice (although not perfect) job predicting the LHC Jet Production and Drell-Yan UE data. I am still hoping for a single tune that will describe all energies!

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton




Do we need a separate tune for each hard QCD subprocess? Jet Production, Drell-Yan Production, etc.

The same tune can describe both Jet Production and Drell-Yan!

Proton Proton


Do we need separate tunes for “Min-Bias” (MB) and the “underlying event” (UE) in a hard scattering process?

PHTHIA Tune Z1 does fairly well at both the UE and MB, but you cannot expect such a naïve approach to be perfect!

PARP(90)

Color

Connections



Kaon ProductionKaon Production

CMS NSD data on the Kshort rapidity distribution at 7 TeV and 900 GeV compared with PYTHIA Tune Z1. The plot shows the average number of Kshort per NSD collision per unit Y, (1/NNSD) dN/dY.

Proton Proton


Kshort Rapidity Distribution: dN/dY

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Y


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NSD (all pT) Tune Z1

CMSKshort Rapidity Distribution: dN/dY

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Y 900 GeV

CMS & ALICE DataPYTHIA Tune Z1

CMS NSD

ALICE INEL pyZ1 NSD = solidpyZ1 INEL = dashed

CMS NSD data on the Kshort rapidity distribution at 900 GeV and the ALICE point at Y = 0 (INEL) compared with PYTHIA Tune Z1. The ALICE point is the average number of Kshort per INEL collision per unit Y at Y = 0, (1/NINEL) dN/dY.

Tune Z1

INEL = NSD + SD

No overall shortage of Kaons in PYTHIA Tune Z1! Kshort

d s s d +

Kshort

d s s d +



Kaon ProductionKaon Production

ALICE INEL data on the charged kaon rapidity distribution at 900 GeV compared with PYTHIA Tune Z1. The plot shows the average number of charged kaons per INEL collision per unit Y at Y = 0, (1/NINEL) dN/dY.

Proton Proton


Charged Kaons Rapidity: dN/dY

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Y


INEL (all pT) 900 GeVpyZ1 NSD = dashedpyZ1 INEL = solid

(K++K-)

Rapidity Distribution Ratio: Kaons/Pions

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(K++K-)/(++-)

ALICE INEL data on the charged kaon to charged pion rapidity ratio at 900 GeV compared with PYTHIA Tune Z1.

ALICE ALICE

Tune Z1 Tune Z1

Rapidity Distribution Ratio: Kshort/Kaons

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Kshort/(K++K-)

No overall shortage of Kaons in PYTHIA Tune Z1! K+

u s K-

u s



Particle Ratios versus PTParticle Ratios versus PT

Proton Proton


PT Particle Ratio: Kaons/Pions

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(K++K-)/(++-)ALICE DataPYTHIA Tune Z1 & Z1C

INEL (|Y| < 0.75) 900 GeV

Z1

Z1C

Tune Z1Cqq/q: 0.1 -> 0.12us/s: 0.4 -> 0.8

Rapidity Distribution Ratio: Kaons/Pions

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ALICE DataPYTHIA Tune Z1 & Z1C


(K++K-)/(++-)

Z1

Z1C

Tune Z1Cqq/q: 0.1 -> 0.12us/s: 0.4 -> 0.8

ALICE INEL data on the charged kaon to charged pion rapidity ratio at 900 GeV compared with PYTHIA Tune Z1.

ALICE INEL data on the charged kaons to charged pions ratio versus pT at 900 GeV (|Y| < 0.75) compared with PYTHIA Tune Z1 & Z1C.

PYTHIA pT dependence off on Kaons!

Tails of the pT distribution. Way off due to the wrong pT!

K+

u s K-

u s



Lambda ProductionLambda Production

CMS NSD data on the Lambda+AntiLambda rapidity distribution at 7 TeV and 900 GeV compared with PYTHIA Tune Z1. The plot shows the average number of particles per NSD collision per unit Y, (1/NNSD) dN/dY.

Proton Proton


(Lam+LamBar) Rapidity Distribution: dN/dY

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Y


900 GeV

7 TeV

NSD (all pT)

(+)_

Rapidity Distribution Ratio: (Lam+LamBar)/(2Kshort)

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7 TeV

NSD (all pT)

(+)/(2Kshort)_

CMS Tune Z1

CMS NSD data on the Lambda+AntiLambda to 2Kshort rapidity ratio at 7 TeV compared with PYTHIA Tune Z1.

CMS

Tune Z1Factor of 1.5!

Oops! Not enough Lambda’s in PYTHIA Tune Z1!

u d s



Cascade ProductionCascade Production

CMS NSD data on the Cascade-+AntiCascade- rapidity distribution at 7 TeV and 900 GeV compared with PYTHIA Tune Z1. The plot shows the average number of particles per NSD collision per unit Y, (1/NNSD) dN/dY.

Proton Proton


(Cas+CasBar) Rapidity Distribution: dN/dY

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Rapidity Y

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Y


900 GeV

7 TeV

NSD (all pT)

( + )_

Rapidity Distribution Ratio: (Cas+CasBar)/(2Kshort)

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7 TeV

NSD (all pT)

( + )/(2Kshort)_

CMS

Tune Z1

CMS data on the Cascade-+AntiCascade- to 2Kshort rapidity ratio at 7 TeV compared with PYTHIA Tune Z1.

CMS

Tune Z1

Factor of 2!

Yikes! Way too few Cascade’s in PYTHIA Tune Z1!

d s s



Particle Ratios versus PTParticle Ratios versus PT

Proton Proton


PT Particle Ratio: (P+Pbar)/Pions

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PT (GeV/c)

PT P

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ALICE DataPYTHIA Tune Z1 & Z1C

INEL (|Y| < 0.75) 900 GeV

Z1

Z1C

Tune Z1Cqq/q: 0.1 -> 0.12us/s: 0.4 -> 0.8

(p+p)/(++-)_

Rapidity Distribution Ratio: (P+Pbar)/Pions

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Rapidity Y

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Y Pa

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(p+p)/(++-)_ALICE Data

PYTHIA Tune Z1 & Z1C

Z1

Z1C

Tune Z1Cqq/q: 0.1 -> 0.12us/s: 0.4 -> 0.8

ALICE INEL data on the Proton+AntiProton to charged pions ratio versus pT at 900 GeV (|Y| < 0.75) compared with PYTHIA Tune Z1 & Z1C.

ALICE INEL data on the Proton+AntiProton to charged pion rapidity ratio at 900 GeV compared with PYTHIA Tune Z1 & Z1C.

PYTHIA way off on the pT dependence of Protons!

Tails of the pT distribution. Way off due to the wrong pT!

Too many overall protons!

p

u u d



Fragmentation SummaryFragmentation Summary Strange Particle & Baryon Yields: PYTHIA is off

on the overall yield of Lambda’s and Cascades (MC below the data) and too high on the proton yield. Difficult to fix this without destroying agreement with LEP!

PT Distributions: PYTHIA does not describe correctly the pT distributions of heavy particles (MC softer than the data). None of the fragmentation parameters I have looked at changes the pT distributions. Hence, if one looks at particle ratios at large pT you can see big discrepancies between data and MC (out in the tails of the distributions)!

Proton Proton


K+

u s

K-

u s

Kshort

d s s d + p

u u d

u d s

d s s

Factorization: Are we seeing a breakdown in factorization between e+e- annihilations and hadron-hadron collisions! Is something happening in hadron-hadron collisions that does not happen in e+e- annihilations?

Herwig++ & Sherpa: Before making any conclusions about fragmentation one must check the predictions of Herwig++ and Sherpa carefully!


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7 TeV ND (all pT)

RDF PreliminaryPYTHIA Tune Z1 (p+p)

_


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7 TeV ND (all pT)

RDF PreliminaryPYTHIA Tune Z1 (+)

_

Beam-meam remnants!Beam-meam remnants!



Sherpa versus PYTHIASherpa versus PYTHIA

Before making any conclusion about e+e- versus pp collisions one must check the predictions of Herwig++ and Sherpa!

Strange particle production in pp at 200 GeV (STAR_2006_S6860818)

Hendrik Hoeth http://users.hepforge.org/~hoeth/STAR_2006_S6860818/

<pT> versus Mass

Sherpa does better than PYTHIA 8!

Documents

PIC 2011, Vancouver August 29, 2011 Rick Field – Florida/CDF/CMSPage 1 Physics in Collision Rick Field University of Florida Outline Examine