Oregon Terascale Workshop March 7, 2011 Rick Field – Florida/CDF/CMSPage 1 Northwest Terascale Workshop Modeling Min-Bias and the Underlying Event Rick

Oregon Terascale Workshop March 7, 2011

Rick Field – Florida/CDF/CMS Page 1

Northwest Terascale WorkshopNorthwest Terascale WorkshopModeling Min-Bias and the Underlying EventModeling Min-Bias and the Underlying Event

Rick FieldUniversity of Florida

UE&MB@CMSUE&MB@CMS

Part 1

Predicting the behavior of the “underlying event” at the LHC. What we expected to see.

CMS

ATLAS

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

University of Oregon March 7-11, 2011

The Underlying Event at the LHC

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

PYTHIA 6.4 Tune Z1: CMS LHC tune (pT-ordered parton showers and new MPI). Comparisons with the LHC UE data.





UE&MB@CMSUE&MB@CMS

Part 2 (tomorrow) How are “min-bias” collisions related to the

“underlying event”.

CMS

ATLAS


Min-Bias Collisions at the LHC

PYTHIA 6.4 Tune Z1: CMS tune (pT-ordered parton showers and new MPI). Comparisons with the LHC Min-Bias data.

How well did we do at predicting the behavior of “min-bias” collisions at the LHC (900 GeV and 7 TeV)?

New Physics in Min-Bias?? Observation of long-range same-side correlations at 7 TeV.

Strange particle production: A problem for the models?

Proton Proton

“Minimum Bias” Collisions



Northwest Terascale WorkshopNorthwest Terascale WorkshopParton Showers and Event Structure at the LHCParton Showers and Event Structure at the LHC

Previous Workshop February 23-27, 2009

The last 2 years have been amazing!We now have a lot of nice LHCdata on the “underlying event”

and min-bias collisions.So much has happened so fast!



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!



QCD Monte-Carlo Models:QCD Monte-Carlo Models:Lepton-Pair ProductionLepton-Pair Production

Start with the perturbative Drell-Yan muon pair production and add initial-state gluon radiation (in the leading log approximation or modified leading log approximation).

Proton AntiProton


Proton AntiProton


Lepton-Pair Production

Lepton

Anti-Lepton


Lepton-Pair Production

Lepton

Anti-Lepton



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-state radiation.

“Jet”

Proton AntiProton

High PT Z-Boson Production

Z-boson

Outgoing Parton

Initial-State Radiation Final-State Radiation

High PT Z-Boson Production

Z-boson

Outgoing Parton



“Hard Scattering” Component



MPI, Pile-Up, and OverlapMPI, Pile-Up, and Overlap MPI: Additional 2-to-2 parton-parton

scatterings within a single hadron-hadron collision.

Pile-Up

Primary

MPI: Multiple Parton Interactions

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton




Pile-Up Proton

Interaction Region z

Proton ProtonProton

Pile-Up: More than one hadron-hadron collision in the beam crossing.

Overlap Overlap: An experimental timing issue where a hadron-hadron collision from the next beam crossing gets included in the hadron-hadron collision from the current beam crossing because the next crossing happened before the event could be read out.



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 Density: dN/dd

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PY Tune A

Min-Bias14 TeV Charged Particles (||<1.0, PT>0.5 GeV/c)

RDF Preliminarygenerator level

PY64 Tune P329

PY64 Tune S320 PY Tune DW

PY Tune DWTPY ATLAS

Transverse Charged Particle DensityTransverse Charged Particle Density

Shows the “associated” charged particle density in the “transverse” region as a function of PTmax for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) for “min-bias” events at 1.96 TeV from PYTHIA Tune A, Tune S320, Tune N324, and Tune P329 at the particle level (i.e. generator level).

PTmax Direction

“Toward”


“Away”


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PY Tune A

PY64 Tune P329

PY64 Tune S320

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

PY64 Tune N324

Min-Bias1.96 TeV

Tevatron LHC

PTmax Direction

“Toward”


“Away”

Extrapolations of PYTHIA Tune A, Tune DW, Tune DWT, Tune S320, Tune P329, and pyATLAS to the LHC.

RDF LHC Prediction!

If the LHC data are not in the range shown here then

we learn new (QCD) physics!Rick Field October 13, 2009



““Transverse” Charged DensityTransverse” Charged Density

PTmax Direction

“Toward”


“Away”

ChgJet#1 Direction

“Toward”


“Away”

Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5 GeV/c, || < 1) at 7 TeV as defined by PTmax, PT(chgjet#1), and PT(muon-pair) from PYTHIA Tune DW at the particle level (i.e. generator level). Charged particle jets are constructed using the Anti-KT algorithm with d = 0.5.


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RDF Preliminarypy Tune DW generator level

PTmax

ChgJet#1

DY(muon-pair)70 < M(pair) < 110 GeV

Muon-Pair Direction

“Toward”


“Away”



Min-Bias “Associated”Min-Bias “Associated”Charged Particle DensityCharged Particle Density

Shows the “associated” charged particle density in the “transverse” region as a function of PTmax for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) for “min-bias” events at 0.2 TeV, 0.9 TeV, 1.96 TeV, 7 TeV, 10 TeV, 14 TeV predicted by PYTHIA Tune DW at the particle level (i.e. generator level).

PTmax Direction

“Toward”


“Away”

PTmax Direction

“Toward”


“Away”

RHIC Tevatron

0.2 TeV → 1.96 TeV (UE increase ~2.7 times)

PTmax Direction

“Toward”


“Away”

LHC

1.96 TeV → 14 TeV (UE increase ~1.9 times)

Linear scale!


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Min-Bias 14 TeV

1.96 TeV

0.2 TeV

7 TeV

0.9 TeV

10 TeV


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Center-of-Mass Energy (TeV)

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PTmax = 5.25 GeV/c

RHIC

Tevatron900 GeV

LHC7

LHC14

LHC10



Min-Bias “Associated”Min-Bias “Associated”Charged Particle DensityCharged Particle Density

Shows the “associated” charged particle density in the “transverse” region as a function of PTmax for charged particles (pT > 0.5 GeV/c, || < 1, not including PTmax) for “min-bias” events at 0.2 TeV, 0.9 TeV, 1.96 TeV, 7 TeV, 10 TeV, 14 TeV predicted by PYTHIA Tune DW at the particle level (i.e. generator level).

Log scale!


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Min-Bias 14 TeV

1.96 TeV

0.2 TeV

7 TeV

0.9 TeV

10 TeV


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0.1 1.0 10.0 100.0

Center-of-Mass Energy (TeV)

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PTmax = 5.25 GeV/c

RHIC

Tevatron

900 GeV

LHC7

LHC14LHC10

PTmax Direction

“Toward”


“Away”

PTmax Direction

“Toward”


“Away”

LHC7 LHC14

7 TeV → 14 TeV (UE increase ~20%)

Linear on a log plot!



Conclusions November 2009Conclusions November 2009 We are making good progress in understanding and modeling the

“underlying event”. RHIC data at 200 GeV are very important!

It is clear now that the default value PARP(90) = 0.16 is not correct and the value should be closer to the Tune A value of 0.25.

The new Pythia pT ordered tunes (py64 S320 and py64 P329) are very similar to Tune A, Tune AW, and Tune DW. At present the new tunes do not fit the data better than Tune AW and Tune DW. However, the new tune are theoretically preferred!

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton




Need to measure “Min-Bias” and the “underlying event” at the LHC as soon as possible to see if there is new QCD physics to be learned!

All tunes with the default value PARP(90) = 0.16 are wrong and are overestimating the activity of min-bias and the underlying event at the LHC! This includes all my “T” tunes and the (old) ATLAS tunes! UE&MB@CMSUE&MB@CMS

Hard-Scattering Cut-Off PT0

1

2

3

4

5

100 1,000 10,000 100,000

CM Energy W (GeV)

PT

0

(Ge

V/c

)

PYTHIA 6.206

= 0.16 (default)

= 0.25 (Set A))

The new and old PYTHIA tunes are beginning to converge and I believe we are finally in a position to make some legitimate predictions at the LHC!



““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”


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

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900 GeV


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” 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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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


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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(G

eV

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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).


0.0

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PT

sum

Den

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(G

eV/c

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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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pyDW + SIM


7 TeV


“Toward”


“Away”



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

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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.

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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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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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

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900 GeV

7 TeV


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PT

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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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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


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.


0.0

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Rat

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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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CMS


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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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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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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

1.0E-02

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1.0E+00

0 5 10 15 20 25 30 35 40

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

1.0E-04

1.0E-03

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0 5 10 15 20 25 30 35 40


Pro

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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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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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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!



ATLAS Tune AMBT1ATLAS Tune AMBT1Judith Katzy LPCC

MB&UE working group meeting, May 31, 2010.

Emily Nurse ICHEP, July 24, 2010.

ATLAS-CONF-2010-031



ATLAS Tune AMBT1ATLAS Tune AMBT1

Attempt to fit a subset of the “min-bias” data (Nchg ≥ 6) where the contamination due to diffraction is expected to be small!

Subset of the “min-bias” data!



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 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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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 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 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



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


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ATLAS publication – arXiv:1012.0791December 3, 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 || < 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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ATLASTune Z1

ATLAS

Factor of 2 increase!

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

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Charge Particle Density

Charge PTsum Density

Rick FieldMPI@LHC 2010 Glasgow, Scotland

December 2, 2010




ATLAS published 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 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 pT > 0.1 GeV/c (|| < 2.5). The data are corrected and compared with PYTHIA Tune Z1 at the generator level.


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ATLAS publication – arXiv:1012.0791December 3, 2010


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

ATLAS-CONF-2011-009February 21, 2011



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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 || < 0.8 and || < 2.5. The data are corrected and compared with PYTHIA Tune Z1 at the generrator 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 || < 0.8 and || < 2.5. The data are corrected and compared with PYTHIA Tune Z1 at the generator level.




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|| < 0.8

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ATLASTune Z1




ATLAS preliminary data at 900 GeV 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 and || < 2.5. The data are corrected and compared with PYTHIA Tune Z1 at the generrator level.

ATLAS preliminary data at 900 GeV 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 and || < 2.5. The data are corrected and compared with PYTHIA Tune Z1 at the generator level.




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ALICE-ATLAS UEALICE-ATLAS UE

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 || < 0.8. The data are corrected and compared with PYTHIA Tune Z1 at the generrator level.



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ALICE-ATLAS UEALICE-ATLAS UE

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 || < 0.8. The data are corrected and compared with PYTHIA Tune Z1 at the generrator level.


ALICETune Z1


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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 Z1 after detector simulation.

CDF published 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.


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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 Z1 after detector simulation.

CDF published 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.


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Oops Tune Z1 is slightly high at CDF!

Tune Z1

Tune Z1




MPI Cut-Off versus the Center-of Mass Energy Wcm: PYTHIA Tune Z1 was determined by fitting pT0 independently at 900 GeV and 7 TeV and calculating = PARP(90). The best fit to pT0 at CDF is slightly higher than the Tune Z1 curve. This is very preliminary! Perhaps with a global fit to all three energies (i.e. “Professor” tune) one can get a simultaneous fit to all three??

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pT0(W)=pT0(W/W0)e




MPI Cut-Off versus the Center-of Mass Energy Wcm: PYTHIA Tune Z1 was determined by fitting pT0 independently at 900 GeV and 7 TeV and calculating = PARP(90). The best fit to pT0 at CDF is slightly higher than the Tune Z1 curve. This is very preliminary! Perhaps with a global fit to all three energies (i.e. “Professor” tune) one can get a simultaneous fit to all three??

pT0(W)=pT0(W/W0) = PARP(90) pT0 = PARP(82) W = Ecm

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More UE activity for W > 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 DW and Tune D6T at the detector level (i.e. Theory + SIM).


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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

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1.0E-06

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1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 5 10 15 20 25 30 35 40 45 50

PTsum (GeV/c)

Pro

bab

ilit

y



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

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 5 10 15 20 25 30 35 40


Pro

bab

ilit

y


Theory + SIM

Normalized to 1


7 TeV



D6T

DW


1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 5 10 15 20 25 30 35 40


Pro

bab

ilit

y


pyZ1 + SIM

Normalized to 1


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

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 5 10 15 20 25 30 35 40 45 50

PTsum (GeV/c)

Pro

bab

ilit

y



Theory + SIM

Normalized to 1



7 TeV

D6T

DW


1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 5 10 15 20 25 30 35 40 45 50

PTsum (GeV/c)

Pro

bab

ilit

y



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!



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

1.0E-04

1.0E-03

1.0E-02

1.0E-01

0 20 40 60 80 100


Pro

ba

bil

ity

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.

Charged Multiplicity Distribution

1.0E-04

1.0E-03

1.0E-02

1.0E-01

0 20 40 60 80 100


Pro

ba

bil

ity

Charged Particles (all PT, ||<2.0)

RDF Preliminarydata CMS NSD


7 TeV

900 GeV


1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 5 10 15 20 25 30 35 40


Pro

bab

ilit

y


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

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 5 10 15 20 25 30 35 40


Pro

bab

ilit

y

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

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 20 40 60 80 100


Pro

bab

ilit

y

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



Summary & ConclusionsSummary & ConclusionsI 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!

Tune Z1 does nice fob of fitting the CMS, ATLAS, and ALICE UE data at 900 GeV and 7 TeV! But Tune Z1 is a little high at CDF (1.96 TeV)! Not bad on MB!

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton




Surprises: more soft particles than expected!, high multiplicity tails (possible new source of “soft” events with high multiplicity?), strange particles and baryons in the UE??

I still dream of a “universal” tune that

fits the UE at all energies! Need to

simultaneously tune LHC plus CDF

(“professor” tune)!

Next Step: More PYTHIA 6.4 and PYTHIA 8 tunes. Time to look more closely at Sherpa and HERWIG++!

CMS UE paper with corrected data using charged particle jets

to appear next week!





UE&MB@CMSUE&MB@CMS

Part 2 (tomorrow) How are “min-bias” collisions related to the

“underlying event”.

CMS

ATLAS


Min-Bias Collisions at the LHC

PYTHIA 6.4 Tune Z1: CMS tune (pT-ordered parton showers and new MPI). Comparisons with the LHC Min-Bias data.

How well did we do at predicting the behavior of “min-bias” collisions at the LHC (900 GeV and 7 TeV)?

New Physics in Min-Bias?? Observation of long-range same-side correlations at 7 TeV.

Strange particle production: A problem for the models?

Proton Proton

“Minimum Bias” Collisions

Documents

Oregon Terascale Workshop March 7, 2011 Rick Field – Florida/CDF/CMSPage 1 Northwest Terascale Workshop Modeling Min-Bias and the Underlying Event Rick