MPI@LHC 2013

MPI@LHC 2013 Antwerp, December 2, 2013

Rick Field – Florida/CDF/CMS Page 1

Outline of Talk

CMS at the LHCCDF Run 2

300 GeV, 900 GeV, 1.96 TeV 900 GeV, 7 & 8 TeV

MPI@LHC 2013MPI@LHC 2013

CDF data from the Tevatron Energy Scan.

The “transMAX”, “transMIN”, “transAVE” and “transDIF” UE observables.

The overall event topology for events with at least 1 charged particle.

Summary & Conclusions.

Mapping out the energy dependence: Tevatron to the LHC!

Comparisions with PYTHIA 6.4 Tune Z1 & Z2* and PYTHIA 8 Tune 4C*.

Tevatron Energy Scan: Findings & Surprises

Rick FieldUniversity of Florida

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation



Tevatron Energy ScanTevatron Energy Scan

Just before the shutdown of the Tevatron CDF has collected more than 10M “min-bias” events at several center-of-mass energies!

Proton

AntiProton

1 mile CDF

Proton AntiProton 1.96 TeV300 GeV

300 GeV 12.1M MB Events

900 GeV 54.3M MB Events

900 GeV



Jet ObservablesJet Observables“Toward” Charged Particle Density: Number of charged particles (pT

> 0.5 GeV/c, || < 0.8) in the “toward” region (not including PTmax) as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2/3, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

PTmax Direction

“Toward”

“Transverse” “Transverse”

“Away”

“Toward” Charged PTsum Density: Scalar pT sum of the charged particles (pT > 0.5 GeV/c, || < 0.8) in the “toward” region (not including PTmax) as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2/3, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

“Away” Charged Particle Density: Number of charged particles (pT > 0.5 GeV/c, || < 0.8) in the “away” region as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2/3, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

“Away” Charged PTsum Density: Scalar pT sum of the charged particles (pT > 0.5 GeV/c, || < 0.8) in the “away” region as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2/3, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

cut = 0.8



UE ObservablesUE Observables“Transverse” Charged Particle Density: Number of charged particles

(pT > 0.5 GeV/c, || < cut) in the “transverse” region as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2/3, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

PTmax Direction

“Toward”


“Away”

“Transverse” Charged PTsum Density: Scalar pT sum of the charged particles (pT > 0.5 GeV/c, || < cut) in the “transverse” region as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2/3, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

“Transverse” Charged Particle Average PT: Event-by-event <pT> = PTsum/Nchg for charged particles (pT > 0.5 GeV/c, || < cut) in the “transverse” region as defined by the leading charged particle, PTmax, averaged over all events with at least one particle in the “transverse” region with pT > 0.5 GeV/c, || < cut.

Zero “Transverse” Charged Particles: If there are no charged particles in the “transverse” region then Nchg and PTsum are zero and one includes these zeros in the average over all events with at least one particle with pT > 0.5 GeV/c, || < cut. However, if there are no charged particles in the “transverse” region then the event is not used in constructing the “transverse” average pT.

cut = 0.8



ObservablesObservables

Overall “Associated” Charged Particle Density: Number of charged particles (pT > 0.5 GeV/c, || < 0.8, not including PTmax) as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

PTmax Direction

“Toward”


“Away”

Overall “Associated” Charged PTsum Density: Scalar pT sum of the charged particles (pT > 0.5 GeV/c, || < 0.8, not including PTmax) as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

Note: The overall “associated” density is equal to the average of the “Towards”, “Away”, and “Transverse” densities.

Overall “Associated” Density = (“Towards” Density + “Away” Density + “Transverse” Density)/3

cut = 0.8

Total Number of Charged Particles: Number of charged particles (pT > 0.5 GeV/c, || < 0.8, including PTmax) as defined by the leading charged particle, PTmax, with at least one particle with pT > 0.5 GeV/c, || < cut.



UE ObservablesUE Observables“transMAX” and “transMIN” Charged Particle Density: Number of

charged particles (pT > 0.5 GeV/c, || < 0.8) in the the maximum (minimum) of the two “transverse” regions as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2/6, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

PTmax Direction

“Toward”

“TransMAX” “TransMIN”

“Away”

“transMAX” and “transMIN” Charged PTsum Density: Scalar pT sum of charged particles (pT > 0.5 GeV/c, || < 0.8) in the the maximum (minimum) of the two “transverse” regions as defined by the leading charged particle, PTmax, divided by the area in - space, 2cut×2/6, averaged over all events with at least one particle with pT > 0.5 GeV/c, || < cut.

Note: The overall “transverse” density is equal to the average of the “transMAX” and “TransMIN” densities. The “TransDIF” Density is the “transMAX” Density minus the “transMIN” Density

“Transverse” Density = “transAVE” Density = (“transMAX” Density + “transMIN” Density)/2

“TransDIF” Density = “transMAX” Density - “transMIN” Density

cut = 0.8Overall “Transverse” = “transMAX” + “transMIN”



““transMIN” & “transDIF”transMIN” & “transDIF”The “toward” region contains the leading “jet”, while the “away”

region, on the average, contains the “away-side” “jet”. The “transverse” region is perpendicular to the plane of the hard 2-to-2 scattering and is very sensitive to the “underlying event”. For events with large initial or final-state radiation the “transMAX” region defined contains the third jet while both the “transMAX” and “transMIN” regions receive contributions from the MPI and beam-beam remnants. Thus, the “transMIN” region is very sensitive to the multiple parton interactions (MPI) and beam-beam remnants (BBR), while the “transMAX” minus the “transMIN” (i.e. “transDIF”) is very sensitive to initial-state radiation (ISR) and final-state radiation (FSR).

“TransDIF” density more sensitive to ISR & FSR.

PTmax Direction


“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

Jet #3

“TransMIN” density more sensitive to MPI & BBR.

0 ≤ “TransDIF” ≤ 2×”TransAVE”

“TransDIF” = “TransAVE” if “TransMIX” = 3×”TransMIN”



PTmax UE DataPTmax UE DataCDF PTmax UE Analysis: “Towards”, “Away”, “transMAX”,

“transMIN”, “transAVE”, and “transDIF” charged particle and PTsum densities (pT > 0.5 GeV/c, || < 0.8) in proton-antiproton collisions at 300 GeV, 900 GeV, and 1.96 TeV (R. Field analysis).

PTmax Direction

“Toward”


“Away”

CMS PTmax UE Analysis: “Towards”, “Away”, “transMAX”, “transMIN”, “transAVE”, and “transDIF” charged particle and PTsum densities (pT > 0.5 GeV/c, || < 0.8) in proton-proton collisions at 900 GeV and 7 TeV (Mohammed Zakaria Ph.D. Thesis, CMS PAS FSQ-12-020).

CMS UE Tunes: PYTHIA 6.4 Tune Z1 (CTEQ5L) and PYTHIA 6.4 Tune Z2* (CTEQ6L) and PYTHIA 8 Tune 4C* (CTEQ6L). All 3 were tuned to the CMS leading chgjet “transAVE” UE data at 900 GeV and 7 TeV.

See the next talk by Mohammed!

Similar to Tune 4C by Corke and Sjöstrand!



Parameter Default

Description

PARP(83) 0.5 Double-Gaussian: Fraction of total hadronic matter within PARP(84)

PARP(84) 0.2 Double-Gaussian: Fraction of the overall hadron radius containing the fraction PARP(83) of the total hadronic matter.

PARP(85) 0.33 Probability that the MPI produces two gluons with color connections to the “nearest neighbors.

PARP(86) 0.66 Probability that the MPI produces two gluons either as described by PARP(85) or as a closed gluon loop. The remaining fraction consists of quark-antiquark pairs.

PARP(89) 1 TeV Determines the reference energy E0.

PARP(82) 1.9 GeV/c

The cut-off PT0 that regulates the 2-to-2 scattering divergence 1/PT4→1/(PT2+PT0

2)2

PARP(90) 0.16 Determines the energy dependence of the cut-off

PT0 as follows PT0(Ecm) = PT0(Ecm/E0) with = PARP(90)

PARP(67) 1.0 A scale factor that determines the maximum parton virtuality for space-like showers. The larger the value of PARP(67) the more initial-state radiation.

Hard Core

Multiple Parton Interaction

Color String

Color String

Multiple Parton Interaction

Color String

Hard-Scattering Cut-Off PT0

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CM Energy W (GeV)P

T0

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= 0.16 (default)

= 0.25 (Set A))

Take E0 = 1.8 TeV

Reference pointat 1.8 TeV

Determine by comparingwith 630 GeV data!

Affects the amount ofinitial-state radiation!

Tuning PYTHIA 6.2:Tuning PYTHIA 6.2:Multiple Parton Interaction ParametersMultiple Parton Interaction Parameters

Determines the energy dependence of the MPI!Remember the energy dependence

of the “underlying event”activity depends on both the = PARP(90) and the PDF!



Total Number of Charged Total Number of Charged ParticlesParticles

Ecm Nchg error NchgDen error

300 GeV 2.241 0.175 0.223 0.017

900 GeV 3.012 0.203 0.300 0.020

1.96 TeV 3.439 0.186 0.342 0.019

7 TeV 4.782 0.063 0.476 0.006

8.0

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CDF and CMS data on the pseudo-rapidity distribution, dN/d, for charged with pT > 0.5 GeV/c and || < 0.8 for events with at least one charged particle with pT > 0.5 GeV/c and || < 0.8.

CDF and CMS data total number of charged particles with pT > 0.5 GeV/c and || < 0.8 for events with at least one charged particle with pT > 0.5 GeV/c and || < 0.8 plotted versus the center-of-mass energy (log scale). The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.

Pseudo-Rapidity Distribution: dN/d

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Number of Charged Particles

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<Nchg> = 4.8!




CDF and CMS data total number of charged particles with pT > 0.5 GeV/c and || < 0.8 for events with at least one charged particle with pT > 0.5 GeV/c and || < 0.8 plotted versus the center-of-mass energy (log scale). The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.


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CDF and CMS data ratio of the total number of charged particles with pT > 0.5 GeV/c and || < 0.8 for events with at least one charged particle with pT > 0.5 GeV/c and || < 0.8 plotted versus the center-of-mass energy (log scale). The data are divided by the value at 300 GeV.

Factor of 2.1 increase! Number of Charged Particles

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CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the total number of charged particles (including PTmax) as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.

Total Number of Charged Particles

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CMS and CDF data on the total number of charged particles (including PTmax) as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.


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““Associated” Charged Particle DensityAssociated” Charged Particle Density

Corrected CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the “associated” charged particle density in the “toward”, “away”, and “transverse” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.

"Associated" Charged Particle Density: dN/dd

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The data are compared with PYTHIA Tune Z1.



““Transverse” Charge Particle Fraction Transverse” Charge Particle Fraction

CMS and CDF data on the fraction of charged particle in the “transverse” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The plot shows the “transverse” Nchg divided by the total Nchg. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.

"Transverse" Fraction of Charged Particles

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Generator Level Theory Tune Z2* (solid lines)Tune 4C* (dashed lines)

Transverse/Total



““Associated” Charged Particle DensityAssociated” Charged Particle Density

Corrected CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the “associated” charged particle density in the “toward”, “away”, and “transverse” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.

"Toward" Charged Particle Density: dN/dd

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““Associated” Charged PTsum DensityAssociated” Charged PTsum Density

Corrected CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the “associated” charged PTsum density in the “toward”, “away”, and “transverse” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.

"Toward" Charged PTsum Density: dPT/dd

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"Away" Charged PTsum Density: dPT/dd

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““transMAX/MIN” NchgDentransMAX/MIN” NchgDen

Corrected CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transMAX” and “transMIN” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.


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““tranMIN” Nchg FractiontranMIN” Nchg Fraction

CMS and CDF data on the fraction of charged particles in the “transMIN” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The plot shows “transMIN” Nchg divided by the overall “transverse” Nchg. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.


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Generator Level Theory Tune Z2* (solid lines)Tune 4C* (dashed lines)

Transverse/Total



““transMAX/MIN” NchgDentransMAX/MIN” NchgDen

Corrected CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transMAX” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty. The data are compared with PYTHIA Tune Z1 and Tune Z2*.

"TransMAX" Charged Particle Density: dN/dd

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"TransMIN" Charged Particle Density: dN/dd

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1.96 TeV

300 GeV

900 GeV

7 TeVRDF Preliminary

Corrected DataGenerator Level Theory


Corrected CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transMIN” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty. The data are compared with PYTHIA Tune Z1 and Tune Z2*.



““transDIF/AVE” NchgDentransDIF/AVE” NchgDen

Corrected CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty. The data are compared with PYTHIA Tune Z1 and Tune Z2*.

Corrected CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transDIF” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty. The data are compared with PYTHIA Tune Z1 and Tune Z2*.

"TransAVE" Charged Particle Density: dN/dd

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300 GeV

900 GeV

7 TeV


"TransDIF" Charged Particle Density: dN/dd

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900 GeV

7 TeV







““transMAX” NchgDen vs EtransMAX” NchgDen vs Ecmcm

Corrected CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transMAX” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.

Corrected CMS and CDF data on the charged particle density in the “transMAX” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale).


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900 GeV

7 TeV



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Center-of-Mass Energy (GeV)

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5.0 < PTmax < 6.0 GeV/c



““Transverse” NchgDen vs ETransverse” NchgDen vs Ecmcm

Corrected CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transMAX” and “transMIN” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale).

Ratio of CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV to the value at 300 GeV for the charged particle density in the “transMAX” and “transMIN” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale).

The data are compared with PYTHIA Tune Z1 and Tune Z2*.


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RDF Preliminary corrected data

generator level theory


"TransMIN"

"TransMAX"

5.0 < PTmax < 6.0 GeV/c

CMS solid dotsCDF solid squares


"Transverse" Charged Particle Density Ratio

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"TransMIN"

Divided by 300 GeV Value"TransMAX"




5.0 < PTmax < 6.0 GeV/c



<transMIN> = 4.7

<transMAX> = 2.7



““Transverse” NchgDen vs ETransverse” NchgDen vs Ecmcm

Corrected CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transAVE” and “transDIF” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale).

Ratio of CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV to the value at 300 GeV for the charged particle density in the “transAVE” and “transDIF” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale).


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"TransDIF"

"TransAVE"

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"TransDIF"

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5.0 < PTmax < 6.0 GeV/c




<transAVE> = 3.1

<transDIF> = 2.2



““TransMIN/DIF” vs ETransMIN/DIF” vs Ecmcm

Ratio of CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV to the value at 300 GeV for the charged particle density in the “transMIN”, and “transDIF” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale).

Ratio of CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV to the value at 300 GeV for the charged PTsum density in the “transMIN”, and “transDIF” regions as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and || < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale).


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"TransDIF"

"TransMIN"5.0 < PTmax < 6.0 GeV/c






"Transverse" Charged PTsum Density Ratio

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"TransDIF"

"TransMIN"

5.0 < PTmax < 6.0 GeV/c







<transMIN> = 4.7

<transDIF> = 2.2

<transMIN> = 5.7

<transDIF> = 2.6

The “transMIN” (MPI-BBR component) increasesmuch faster with center-of-mass energy

than the “transDIF” (ISR-FSR component)!Duh!!



““Tevatron” to the LHCTevatron” to the LHC

Tune Z2* & 4C*CDF

CDF

CDF

CMS"TransAVE" Charged Particle Density: dN/dd

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1.96 TeV

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13 TeV PredictedRDF Preliminary

Corrected DataGenerator Level Theory

Tune Z2* (solid lines)Tune 4C* (dashed lines)



““Tevatron” to the LHCTevatron” to the LHC

Tune Z2* & 4C*CDF

CDF

CDF

CMS"TransAVE" Charged PTsum Density: dPT/dd

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PT

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(G

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13 TeV Predicted

Tune Z2* (solid lines)Tune 4C* (dashed lines)





Summary & ConclusionsSummary & Conclusions

The “transMIN” (MPI-BBR component) increases much faster with center-of-mass energy than the “transDIF” (ISR-FSR component)! Previously we only knew the energy dependence of “transAVE”.

The “transverse” density increases faster with center-of-mass energy than the overall density (Nchg ≥ 1)! However, the “transverse” = “transAVE” region is not a true measure of the energy dependence of MPI since it receives large contributions from ISR and FSR.

We now have at lot of MB & UE data at300 GeV, 900 GeV, 1.96 TeV, and 7 TeV!

We can study the energy dependence more precisely than ever before!

PYTHIA 6.4 Tune Z1 & Z2* and PYTHIA 8 Tune 4C* do a fairly good job in describing the energy deperdence of the UE, however there is room for improvement! The parameterization PT0(Ecm) = PT0(Ecm/E0) seems to work!

What we are learning shouldallow for a deeper understanding of MPI

which will result in more precisepredictions at the future

LHC energies of 13 & 14 TeV!

Date post:	27-Jan-2016
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MPI@LHC 2013

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