Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 1
11stst Workshop on Energy Scaling Workshop on Energy Scalingin Hadron-Hadron Collisionsin Hadron-Hadron Collisions
Rick FieldUniversity of Florida
Outline of Talk
Proton AntiProton
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Initial-State Radiation
Final-State Radiation
CMS at the LHCCDF Run 2
Extrapolating “min-bias” collisions to the LHC.
LHC predictions!
Studying <pT> versus Nchg in “min-bias” collisions and in Drell-Yan.
From CDF to CMSFermilab 2009
Summary.
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 2
Charged Particle Density: dN/dCharged Particle Density: dN/dCharged Particle Density: dN/d
0.0
1.0
2.0
3.0
4.0
5.0
-8 -6 -4 -2 0 2 4 6 8
PseudoRapidity
Ch
arg
ed
Par
ticl
e D
en
sit
y
Min-Bias1.96 TeV
PY Tune A
PY64 Tune P329
RDF Preliminarygenerator level
PY64 Tune S320
Charged Particles (all PT)
Charged Particle Density: dN/d
0.0
0.5
1.0
1.5
2.0
-8 -6 -4 -2 0 2 4 6 8
PseudoRapidity
Ch
arg
ed
Par
ticl
e D
en
sit
y
RDF Preliminarygenerator level
Charged Particles (PT>0.5 GeV/c)
Min-Bias1.96 TeV
PY64 Tune P329
PY Tune A
PY64 Tune S320
Charged particle (all pT) pseudo-rapidity distribution, dNchg/dd, at 1.96 TeV for inelastic non-diffractive collisions from PYTHIA Tune A, Tune S320, and Tune P324.
Charged particle (pT>0.5 GeV/c) pseudo-rapidity distribution, dNchg/dd, at 1.96 TeV for inelastic non-diffractive collisions from PYTHIA Tune A, Tune S320, and Tune P324.
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 3
Charged Particle Density: dN/dCharged Particle Density: dN/d
Proton AntiProton
“Minumum Bias” Collisions
Tevatron LHC
Extrapolations of PYTHIA Tune A, Tune S320, and Tune P329 to the LHC.
Charged Particle Density: dN/d
0.0
1.0
2.0
3.0
4.0
5.0
-8 -6 -4 -2 0 2 4 6 8
PseudoRapidity
Ch
arg
ed
Part
icle
De
ns
ity
Min-Bias1.96 TeV
PY Tune A
PY64 Tune P329
RDF Preliminarygenerator level
PY64 Tune S320
Charged Particles (all PT)
Charged Particle Density: dN/d
0.0
2.0
4.0
6.0
8.0
-8 -6 -4 -2 0 2 4 6 8
PseudoRapidity
Ch
arg
ed
Pa
rtic
le D
en
sit
y
RDF Preliminarygenerator level
Charged Particles (all PT) Min-Bias14 TeV
PY Tune A
PY64 Tune P329
PY64 Tune S320
Charged particle (all pT) pseudo-rapidity distribution, dNchg/dd, at 1.96 TeV for inelastic non-diffractive collisions from PYTHIA Tune A, Tune S320, and Tune P324.
Proton Proton
“Minumum Bias” Collisions
RDF LHC Prediction!
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 4
Charged Particle Density: dN/dCharged Particle Density: dN/d
Proton AntiProton
“Minumum Bias” Collisions
Tevatron LHC
Extrapolations of PYTHIA Tune A, Tune S320, and Tune P329 to the LHC.
Charged particle (pT > 0.5 GeV/c) pseudo-rapidity distribution, dNchg/dd, at 1.96 TeV for inelastic non-diffractive collisions from PYTHIA Tune A, Tune S320, and Tune P324.
Proton Proton
“Minumum Bias” Collisions
Charged Particle Density: dN/d
0.0
0.5
1.0
1.5
2.0
-8 -6 -4 -2 0 2 4 6 8
PseudoRapidity
Ch
arg
ed
Part
icle
De
ns
ity
RDF Preliminarygenerator level
Charged Particles (PT>0.5 GeV/c)
Min-Bias1.96 TeV
PY64 Tune P329
PY Tune A
PY64 Tune S320
Charged Particle Density: dN/d
0.0
1.0
2.0
3.0
4.0
-8 -6 -4 -2 0 2 4 6 8
PseudoRapidity
Ch
arg
ed
Pa
rtic
le D
en
sit
y
RDF Preliminarygenerator level
Charged Particles (PT>0.5 GeV/c) Min-Bias14 TeV
PY64 Tune P329
PY Tune A
PY64 Tune S320
RDF LHC Prediction!
Charged Particle Density: dN/d
0.0
1.0
2.0
3.0
4.0
-8 -6 -4 -2 0 2 4 6 8
PseudoRapidity
Ch
arg
ed
Pa
rtic
le D
en
sity
RDF Preliminarygenerator level
Charged Particles (PT>0.5 GeV/c) Min-Bias14 TeV
PY64 Tune P329
PY Tune A
PY64 Tune S320
PY Tune DWT
Why is py64 Tune P329 higher than py Tune DWT??
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 5
Min-Bias CorrelationsMin-Bias Correlations
Data at 1.96 TeV on the average pT of charged particles versus the number of charged particles (pT > 0.4 GeV/c, || < 1) for “min-bias” collisions at CDF Run 2. The data are corrected to the particle level and are compared with PYTHIA Tune A at the particle level (i.e. generator level).
Proton AntiProton
“Minumum Bias” Collisions
Average PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 10 20 30 40 50
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
Charged Particles (||<1.0, PT>0.4 GeV/c)
Min-Bias1.96 TeV
ATLAS
pyA
pyDW
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 6
Min-Bias: Average PT versus NchgMin-Bias: Average PT versus Nchg
Proton AntiProton
“Soft” Hard Core (no hard scattering)
Proton AntiProton
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Initial-State Radiation
Final-State Radiation
“Hard” Hard Core (hard scattering)
CDF “Min-Bias”
= +
Average PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35 40
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
Charged Particles (||<1.0, PT>0.4 GeV/c)
Min-Bias1.96 TeV
pyAnoMPI
ATLAS
pyA
Proton AntiProton
Multiple-Parton Interactions
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Final-State Radiation
Initial-State Radiation
+
Beam-beam remnants (i.e. soft hard core) produces low multiplicity and small <pT> with <pT> independent of the multiplicity.
Hard scattering (with no MPI) produces large multiplicity and large <pT>.
Hard scattering (with MPI) produces large multiplicity and medium <pT>.
The CDF “min-bias” trigger picks up most of the “hard
core” component!
This observable is sensitive to the MPI tuning!
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 7
Average PT versus NchgAverage PT versus Nchg
Proton AntiProton
“Minumum Bias” Collisions
Proton AntiProton
Drell-Yan Production
Anti-Lepton
Lepton
Underlying Event Underlying Event
Data at 1.96 TeV on the average pT of charged particles versus the number of charged particles (pT > 0.4 GeV/c, || < 1) for “min-bias” collisions at CDF Run 2. The data are corrected to the particle leveland are compared with PYTHIA Tune A, Tune DW, and the ATLAS tune at the particle level (i.e. generator level).
Particle level predictions for the average pT of charged particles versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2.
Average PT versus Nchg
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarygenerator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
pyAW
ATLAS
Average PT versus Nchg
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
pyAW
ATLAS
Average PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35 40
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
Charged Particles (||<1.0, PT>0.4 GeV/c)
Min-Bias1.96 TeV
pyAnoMPI
ATLAS
pyA
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 8
Average PT versus NchgAverage PT versus Nchg
Proton AntiProton
Drell-Yan Production (no MPI)
Anti-Lepton
Lepton
Underlying Event Underlying Event
Average PT versus Nchg
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
pyAW
ATLAS
Proton AntiProton
Drell-Yan Production (with MPI)
Anti-Lepton
Lepton
Underlying Event Underlying Event
Drell-Yan
Proton AntiProton
High PT Z-Boson Production
Z-boson
Outgoing Parton
Initial-State Radiation Final-State Radiation
= +
Z-boson production (with low pT(Z) and no MPI) produces low multiplicity and small <pT>.
+
High pT Z-boson production produces large multiplicity and high <pT>.
Z-boson production (with MPI) produces large multiplicity and medium <pT>.
No MPI!
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 9
Average PT(Z) versus NchgAverage PT(Z) versus Nchg
Proton AntiProton
Drell-Yan Production
Anti-Lepton
Lepton
Underlying Event Underlying Event
Data on the average pT of charged particles versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2. The data are corrected to the particle level and are compared with various Monte-Carlo tunes at the particle level ( i.e. generator level).
Average PT versus Nchg
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
pyAW
ATLAS
PT(Z-Boson) versus Nchg
0
20
40
60
80
0 5 10 15 20 25 30 35 40
Number of Charged Particles
Ave
rag
e P
T(Z
) (G
eV
/c)
CDF Run 2 Preliminarygenerator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
pyAW
HW
JIM
ATLAS
No MPI!
Predictions for the average PT(Z-Boson) versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV) at CDF Run 2.
PT(Z-Boson) versus Nchg
0
20
40
60
80
0 5 10 15 20 25 30 35 40
Number of Charged Particles
Ave
rag
e P
T(Z
) (G
eV/c
)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
pyAW
HW
JIM
ATLAS
Proton AntiProton
High PT Z-Boson Production
Z-boson
Outgoing Parton
Initial-State Radiation
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 10
Average PT versus NchgAverage PT versus Nchg
Proton AntiProton
Drell-Yan Production
Anti-Lepton
Lepton
Underlying Event Underlying Event
Predictions for the average pT of charged particles versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV, PT(pair) < 10 GeV/c) at CDF Run 2.
Average Charged PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarygenerator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
PT(Z) < 10 GeV/c
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
pyAW
Average Charged PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarygenerator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
PT(Z) < 10 GeV/c
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
ATLAS
pyAW
Average Charged PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 5 10 15 20 25 30 35
Number of Charged Particles
Ave
rag
e P
T (
GeV
/c)
CDF Run 2 Preliminarydata corrected
generator level theory
"Drell-Yan Production"70 < M(pair) < 110 GeV
PT(Z) < 10 GeV/c
Charged Particles (||<1.0, PT>0.5 GeV/c)excluding the lepton-pair
HW
JIM
ATLAS
pyAW
Data the average pT of charged particles versus the number of charged particles (pT > 0.5 GeV/c, || < 1, excluding the lepton-pair) for for Drell-Yan production (70 < M(pair) < 110 GeV, PT(pair) < 10 GeV/c) at CDF Run 2. The data are corrected to the particle level and are compared with various Monte-Carlo tunes at the particle level (i.e. generator level).
PT(Z) < 10 GeV/c
No MPI!
Average PT versus Nchg
0.6
0.8
1.0
1.2
1.4
0 10 20 30 40
Number of Charged Particles
Ave
rag
e P
T (
Ge
V/c
)
CDF Run 2 Preliminarydata corrected
generator level theory
Charged Particles (||<1.0)pyA
Min-Bias PT > 0.4 GeV/c
Drell-Yan PT > 0.5 GeV PT(Z) < 10 GeV/c
pyAW
Proton AntiProton
“Minumum Bias” Collisions Remarkably similar behavior! Perhaps indicating that MPI playing an important role in
both processes.
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 11
LHC PredictionsLHC Predictions
Proton AntiProton
“Minumum Bias” Collisions
Proton AntiProton
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Initial-State Radiation
Final-State Radiation
Proton AntiProton
Drell-Yan Production
Anti-Lepton
Lepton
Underlying Event Underlying Event
Charged Particle Density: dN/d
0.0
1.0
2.0
3.0
4.0
-8 -6 -4 -2 0 2 4 6 8
PseudoRapidity
Ch
arg
ed P
arti
cle
Den
sity
RDF Preliminarygenerator level
Charged Particles (PT>0.5 GeV/c) Min-Bias14 TeV
PY64 Tune P329
PY Tune A
PY64 Tune S320
"Transverse" Charged Particle Density: dN/dd
0.0
0.4
0.8
1.2
1.6
0 5 10 15 20 25
PTmax (GeV/c)
"Tra
ns
ve
rse
" C
ha
rge
d D
en
sit
y
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 DWT
"Toward" Charged Particle Density: dN/dd
0.0
0.4
0.8
1.2
1.6
0 25 50 75 100 125 150
Lepton-Pair PT (GeV/c)
"To
war
d"
Ch
arg
ed D
ensi
tyDrell-Yan
14 TeV
70 < M(pair) < 110 GeV
Charged Particles (||<1.0, PT>0.5 GeV/c)
RDF Preliminarygenerator level
PY Tune DWT PY Tune DW
PY64 Tune P329 PY64 Tune S320
The amount of activity in “min-bias” collisions.
I believe we are now in a position to make some predictions at the LHC!
PTmax Direction
“Toward”
“Transverse” “Transverse”
“Away”
Z-BosonDirection
“Toward”
“Transverse” “Transverse”
“Away”
The amount of activity in the “underlying event” in hard scattering events.
The amount of activity in the “underlying event” in Drell-Yan events.
If the LHC data are not in the range shown here then
we learn new physics!
Fermilab Energy Scaling Workshop April 29, 2009
Rick Field – Florida/CDF/CMS Page 12
SummarySummary We are making good progress in understanding and modeling the
“underlying event”.
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 and Tune DW. At present the new tunes do not fit the data better than Tune A and Tune DW. However, the new tune are theoretically preferred!
Proton AntiProton
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Initial-State Radiation
Final-State Radiation
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 the 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))
However, I believe that the better fits to the LEP
fragmentation data at high z will lead to small improvements
of Tune A at the Tevatron!