Perspectives on Physics and on
CMS at Very High Luminosity
Are the QCD MC Models Ready for High Luminosity?
Rick Field
University of Florida
Alushta, Crimea, Ukraine, May 2012
Outline
Outgoing Parton
 How Universal are the QCD MC Model Tunes?
• Do we need a separate tune for each center-of-mass
•
•
energy? 900 GeV, 1.96 TeV, 7 TeV, etc.
Do we need a separate tune for each hard QCD
subprocess? Jet Production, Drell-Yan Production, etc.
Do we need separate tunes for “Min-Bias” (MB) and the
“underlying event” (UE) in a hard scattering process?
 A close look at two PYTHIA tunes:
• PYTHIA 6.2 Tune DW (CDF UE tune).
• PYTHIA 6.4 Tune Z1 (CMS UE tune).
PT(hard)
Initial-State Radiation
Proton
Underlying Event
Outgoing Parton
Final-State
Radiation
High PT Z-Boson Production
Outgoing Parton
Initial-State Radiation
Proton
AntiProton
Z-boson
 Pile-Up: A quick look at the fluctuations in pile-up.
 New CDF UE Data: The Tevatron Energy Scan (300 GeV,
Proton
Underlying Event
“Minimum Bias” Collisions
Proton
Proton
900 GeV, 1.96 TeV).
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 1
QCD Monte-Carlo Models:
High Transverse Momentum Jets
Hard Scattering
Initial-State Radiation
Hard Scattering “Jet”
Initial-State Radiation
“Jet”
Outgoing Parton
PT(hard)
Outgoing Parton
PT(hard)
Proton
“Hard Scattering” Component
AntiProton
Final-State Radiation
Outgoing Parton
Underlying Event
Underlying Event
Proton
“Jet”
Final-State Radiation
AntiProton
Underlying Event
Outgoing Parton
Underlying Event
“Underlying Event”
 Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and finalstate gluon radiation (in the leading log approximation or modified leading log approximation).
 The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or
semi-soft multiple parton interactions (MPI).
The “underlying
event” is“jet”
an unavoidable
 Of course the outgoing colored partons fragment
into hadron
and inevitably “underlying event”
background to most collider observables
observables receive contributions from initial
and final-state radiation.
and having good understand of it leads to
more precise collider measurements!
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 2
QCD Monte-Carlo Models:
Lepton-Pair Production
Lepton-Pair
Production
High
PT Z-Boson
Production
Anti-Lepton
Outgoing Parton
Initial-State
Initial-State Radiation
Radiation
High P
T Z-Boson Production
Lepton-Pair
Production
Initial-State
Initial-StateRadiation
Radiation
“Jet”
Proton
Proton
Final-State Radiation
Outgoing
Parton
Anti-Lepton
Final-State Radiation
“Hard Scattering” Component
AntiProton
AntiProton
Underlying Event
Lepton
Z-boson
Underlying Event
Proton
Lepton
Z-boson
AntiProton
Underlying Event
Underlying Event
“Underlying Event”

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).
 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.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 3
Traditional Approach
CDF Run 1 Analysis Charged Particle Df Correlations
Leading Calorimeter Jet or
Charged Jet #1
Leading Charged Particle Jet or
PT > PTmin |h| < hcut
Direction
Leading Charged Particle or
2
“Transverse” region
very sensitive to the
“underlying event”!
Away RegionZ-Boson
“Toward-Side” Jet
Df
“Toward”
“Transverse”
“Transverse”
“Away”
Leading Object
Direction
Df
“Toward”
“Transverse”
“Transverse”
Transverse
Region
f
Leading
Object
Toward Region
Transverse
Region
“Away”
Away Region
0
-hcut
“Away-Side” Jet
h
+hcut
 Look at charged particle correlations in the azimuthal angle Df relative to a leading object (i.e.
CaloJet#1, ChgJet#1, PTmax, Z-boson). For CDF PTmin = 0.5 GeV/c hcut = 1.
 Define |Df| < 60o as “Toward”, 60o < |Df| < 120o as “Transverse”, and |Df| > 120o as

“Away”.
o
All three regions have the same area in h-f space, Dh×Df = 2hcut×120 = 2hcut×2/3. Construct
densities by dividing by the area in h-f space.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 4
“Transverse” Charged Density
PTmax Direction
"Transverse" Charged Particle Density: dN/dhdf
Df
1.6
“Transverse”
“Transverse”
“Away”
ChgJet#1 Direction
Df
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Density
“Toward”
RDF Preliminary
7 TeV
py Tune DW generator level
1.2
PTmax
0.8
ChgJet#1
DY(muon-pair)
70 < M(pair) < 110 GeV
0.4
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
Muon-Pair Direction
Df
0
5
10
15
20
25
30
35
40
45
50
PT(chgjet#1) or PTmax or PT(pair) (GeV/c)
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, |h| < 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.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 5
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.2
RDF Preliminary
14 TeV
Min-Bias
"Transverse" Charged Density
"Transverse" Charged Density
1.2
py Tune DW generator level
10 TeV
7 TeV
0.8
1.96 TeV
0.9 TeV
0.4
0.2 TeV
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
RDF Preliminary
LHC14
py Tune DW generator level
0.8
LHC10
LHC7
Tevatron
900 GeV
0.4
PTmax = 5.25 GeV/c
RHIC
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
0
25
2
Df
“Toward”
RHIC
“Transverse”
“Transverse”
0.2 TeV → 1.96 TeV
(UE increase ~2.7 times)
Tevatron
“Away”
6
8
10
12
14
Center-of-Mass Energy (TeV)
PTmax (GeV/c)
PTmax Direction
4
PTmax Direction
Df
“Toward”
“Transverse”
PTmax Direction
1.96 TeV → 14 TeV
(UE increase ~1.9 times)
LHC
“Transverse”
“Away”
Df
“Toward”
“Transverse”
“Transverse”
“Away”
 Shows the “associated” charged particle density in the “transverse” region as a function of
PTmax for charged particles (pT > 0.5 GeV/c, |h| < 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
Linear scale!
level (i.e. generator level).
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 6
PYTHIA Tune DW
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
Charged Particle Density
CMS Preliminary
"Transverse" Charged Density
1.2
7 TeV
data uncorrected
pyDW + SIM
0.8
CMS
900 GeV
0.4
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.2
RDF Preliminary
7 TeV
ATLAS corrected data
Tune DW generator level
0.8
ATLAS
900 GeV
0.4
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
30
35
40
45
0
50
2
4
6
8
10
12
14
16
18
20
PTmax (GeV/c)
PT(chgjet#1) GeV/c
Charged Particle Density
 CMS preliminary data at 900 GeV and 7 TeV  ATLAS preliminary data at 900 GeV and 7
"Transverse" Charged Particle Density: dN/dhdf
TeV on the “transverse” charged particle
on the “transverse” charged
particle density,
1.2
Preliminary
density,
dN/dhdf, as defined by the leading
dN/dhdf, as defined by theRDF
leading
charged
CDF 1.96 TeV
data corrected
charged
(PTmax) for charged particles
pyDW generatorparticles
level
particle jet (chgjet#1) for charged
Leading particle
Jet
with pT > 0.5 GeV/c and |h| < 2.5. The data are
with pT > 0.5 GeV/c and0.8|h| < 2. The data are
corrected and compared with PYTHIA Tune
uncorrected and compared with PYTHIA
DW at the generator level.
Tune DW after detector simulation.
PT(chgjet#1) Direction
0.4
PTmax Direction
Df
“Toward”
“Transverse”
Df
Charged Particles (PT>0.5 GeV/c, |h| < 1.0)
0.0
“Transverse”
“Transverse”
0
“Away”
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
“Toward”
50
100
150
200
250
PT(jet#1) GeV/c
Rick Field – Florida/CDF/CMS
300
350
“Transverse”
400
“Away”
Page 7
PYTHIA Tune DW
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
3.0
1.2
CMS Preliminary
7 TeV
data uncorrected
pyDW + SIM
Ratio: 7 TeV/900 GeV
Charged Particle Density
CMS Preliminary
0.8
Ratio
CMS
900 GeV
0.4
data uncorrected
pyDW + SIM
2.0
CMS
1.0
7 TeV / 900 GeV
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
30
35
40
45
50
0
2
4
6
8
10
12
14
16
18
PT(chgjet#1) (GeV/c)
PT(chgjet#1) GeV/c
 CMS preliminary data at 900 GeV and 7 TeV  Ratio of CMS preliminary data at 900 GeV and
7 TeV on the “transverse” charged particle
on the “transverse” charged particle density,
density, dN/dhdf, as defined by the leading
dN/dhdf, as defined by the leading charged
charged particle jet (chgjet#1) for charged
particle jet (chgjet#1) for charged particles
particles with pT > 0.5 GeV/c and |h| < 2. The
with pT > 0.5 GeV/c and |h| < 2. The data are
data are uncorrected and compared with
uncorrected and compared with PYTHIA
PYTHIA Tune DW after detector simulation.
Tune DW after detector simulation.
PT(chgjet#1) Direction
PT(chgjet#1) Direction
Df
Df
“Toward”
“Transverse”
“Toward”
“Transverse”
“Transverse”
“Away”
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 8
Charged Particle Density
1.96 TeV
data corrected
pyDW generator level
Charged Particle Density
Average Charged Density
3
Drell-Yan Production
70 < M(pair) < 110 GeV
2
1
Average Charged Density
Large increase in the UE
in going from 1.96 TeV
Charged Particle Density: dN/dhdf
Charged Particle Density: dN/dhdf
"Toward" Charged Particle Density: dN/dhdf
to 7 TeV as predicted by
3
Tune DW! 1.2 RDF Preliminary
CDF RunPYTHIA
2
CMS Preliminary
data corrected
"Away"
pyDW generator level
0.8
Drell-Yan
Production
Charged Particles
(|h|<1.0, PT>0.5
GeV/c)
excluding the lepton-pair
0
10
20
30
40
50
60
0
70
PT(lepton-pair) GeV/c
80
20
90
Initial-State Radiation
“Transverse”
“Transverse”
“Away”
"Toward"
Charged Particles (PT>0.5 GeV/c)
0 60
PT(lepton-pair) GeV/c
Outgoing Parton
T
"Transverse"
1
100
40
High P Z-Boson Production
CDF:DfProton-Antiproton
Collisions at 1.96 GeV
Lepton Cuts: pT > 20 GeV |h| < 1.0
“Toward”
Proton
Mass Cut:
70 < M(lepton-pair) < 110
GeV
AntiProton
Charged Particles: pT > 0.5 GeV/c |h| < 1.0
Z-Boson Direction
"Away"
Drell-Yan Production
60 < M(pair) < 120 GeV
2
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
excluding the lepton-pair
0
0.0
0
CMS
CDF 1.96 TeV
0.4
"Transverse"
"Toward"
7 TeV
data corrected
CMS pyDW
7 TeV
generator level
2080
40
100
60
80
100
PT(lepton-pair) GeV/c
High P Z-Boson Production
CMS: Proton-Proton
Collisions at 7 GeV
Df
Lepton Cuts: pT > 20 GeV |h| < 2.4
“Toward”
Mass Cut:Proton
60 < M(lepton-pair) < 120 Proton
GeV
Charged Particles: pT > 0.5 GeV/c |h| < 2.0
Z-Boson Direction
Outgoing Parton
T
Initial-State Radiation
“Transverse”
“Transverse”
“Away”
Z-boson
Z-boson
 CDF data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 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 density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 2 for DrellYan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with
PYTHIA Tune DW.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 9
PYTHIA Tune DW
Charged Particle Density: dN/dhdf
"Toward" Charged Particle Density: dN/dhdf
3
1.2
CMS
7 TeV
data corrected
pyDW generator level
"Away"
Drell-Yan Production
60 < M(pair) < 120 GeV
2
Charged Particle Density
Average Charged Density
CMS Preliminary
data corrected
pyDW generator level
CMS 7 TeV
0.8
CDF 1.96 TeV
Overall PYTHIA0.4Tune DW
"Toward"
is in amazingly good agreement
with the
Charged Particles (PT>0.5 GeV/c)
Drell-Yan Production
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
excluding
the
lepton-pair
Tevatron Jet production 0.0
and Drell-Yan data
20
40
60 did a very
80
100 job in
0 predicting
20
60
80
and
good
the40
PT(lepton-pair) GeV/c
PT(lepton-pair) GeV/c
LHC Jet production and Drell-Yan data!
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
(although not perfect)
"Transverse"
1
0
0
1.5
100
1.5
RDF Preliminary
RDF Preliminary
data corrected
pyDW generator level
Charged Particle Density
Charged Particle Density
RDF Preliminary
CMS 7 TeV
1.0
CDF 1.96 TeV
0.5
CMS 900 GeV
CMS 7 TeV
data corrected
pyDW generator level
1.0
CDF 1.96 TeV
0.5
CMS 900 GeV
Charged Particles (PT>0.5 GeV/c)
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
0
20
40
60
80
100
0
PT(chgjet#1 or jet#1) GeV/c
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
50
100
150
200
250
PT(chgjet#1 or jet#1) GeV/c
Rick Field – Florida/CDF/CMS
Page 10
300
CMS UE Data
"Transverse" Charged PTsum Density: dPT/dhdf
"Transverse" Charged Particle Density: dN/dhdf
2.0
CMS Preliminary
CMS Preliminary
data corrected
Tune Z1 generator level
7 TeV
PTsum Density (GeV/c)
Charged Particle Density
1.6
1.2
0.8
900 GeV
CMS
0.4
Tune Z1
data corrected
Tune Z1 generator level
1.6
7 TeV
1.2
CMS
0.8
900 GeV
Tune Z1
0.4
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0.0
0
10
20
30
40
50
60
70
80
90
100
0
10
PT(chgjet#1) GeV/c
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
30
40
50
60
70
80
90
100
PT(chgjet#1) GeV/c
 CMS preliminary data at 900 GeV and 7
TeV on the “transverse” charged particle
density, dN/dhdf, as defined by the leading
charged particle jet (chgjet#1) for charged
particles with pT > 0.5 GeV/c and |h| < 2.0.
The data are corrected and compared with
PYTHIA Tune Z1 at the generator level.
CMS corrected
data!
20
 CMS preliminary data at 900 GeV and 7
TeV on the “transverse” charged PTsum
density, dPT/dhdf, as defined by the leading
charged particle jet (chgjet#1) for charged
particles with pT > 0.5 GeV/c and |h| < 2.0.
The data are corrected and compared with
PYTHIA Tune Z1 at the generator level.
Very nice agreement!
Rick Field – Florida/CDF/CMS
CMS corrected
data!
Page 11
ATLAS UE Data
"Transverse" Charged PTsum Density: dPT/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.5
RDF Preliminary
RDF Preliminary
7 TeV
ATLAS corrected data
Tune Z1 generator level
PTsum Density (GeV/c)
"Transverse" Charged Density
1.2
0.8
ATLAS
900 GeV
0.4
Tune Z1
7 TeV
ATLAS corrected data
Tune Z1 generator level
1.0
ATLAS
900 GeV
0.5
Tune Z1
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
0
5
10
15
20
25
PTmax (GeV/c)
PTmax (GeV/c)
 ATLAS published data at 900 GeV and 7
TeV on the “transverse” charged particle
density, dN/dhdf, as defined by the leading
charged particle (PTmax) for charged
particles with pT > 0.5 GeV/c and |h| < 2.5.
The data are corrected and compared with
PYTHIA Tune Z1 at the generator level.
 ATLAS published data at 900 GeV and 7
TeV on the “transverse” charged PTsum
density, dPT/dhdf, as defined by the leading
charged particle (PTmax) for charged
particles with pT > 0.5 GeV/c and |h| < 2.5.
The data are corrected and compared with
PYTHIA Tune Z1 at the generrator level.
ATLAS publication – arXiv:1012.0791
December 3, 2010
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 12
PYTHIA Tune Z1
Tune Z1 describes the
energy dependence
Charged Particle Density: dN/dhdf
Charged Particle Density: dN/dhdf
"Toward" Charged Particle Density: dN/dhdf
fairly well!
3
1.2
Drell-Yan Production
70 < M(pair) < 110 GeV
2
1
CMS Preliminary
RDF Preliminary
1.96 TeV
data corrected
pyZ1 generator level
Charged Particle Density
Average Charged Density
CDF Run 2
Average Charged Density
3
data corrected
"Away"
pyZ1 generator level
0.8
Charged Particles
(|h|<1.0, Production
PT>0.5 GeV/c)
Drell-Yan
excluding the lepton-pair
0
10
20
30
40
50
60
0
70
80
20
PT(lepton-pair) GeV/c
Z-Boson Direction
Df
High PT Z-Boson Production
90
"Transverse"
1
"Toward"
0
100
40
0 60
2080
40
100
Z-Boson Direction
Df
High PT Z-Boson Production
Initial-State Radiation
80
100
Outgoing Parton
Initial-State Radiation
“Toward”
“Toward”
Proton
“Transverse”
60
PT(lepton-pair) GeV/c
PT(lepton-pair) GeV/c
Outgoing Parton
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
excluding the lepton-pair
Charged Particles (PT>0.5 GeV/c)
0.0
0
"Away"
Drell-Yan Production
60 < M(pair) < 120 GeV
2
CDF 1.96 TeV
0.4
"Transverse"
"Toward"
CMS
7 TeV
data corrected
pyZ1
generator level
CMS 7
TeV
Proton
AntiProton
“Transverse”
“Transverse”
“Away”
Proton
“Transverse”
“Away”
Z-boson
Z-boson
 CDF data at 1.96 TeV on the density of charged particles, dN/dhdf, with pT > 0.5 GeV/c and |h| < 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/dhdf, with pT > 0.5 GeV/c and |h| < 2 for DrellYan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with
PYTHIA Tune Z1.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 13
PYTHIA Tune Z1
"Transverse"Charged
ChargedParticle
ParticleDensity:
Density:dN/dhdf
dN/dhdf
"Transverse"
1.2
"Transverse" Charged Particle Density: dN/dhdf
1.5
CMSPreliminary
Preliminary
RDF
RDF Preliminary
data
corrected
data
corrected
Tune generator
Z1 generator
level
pyZ1
level
CMS 7 TeV7 TeV
Charged Particle Density
Charged
Charged Particle
Particle Density
Density
1.6
1.5
1.0
CDF 1.96 TeV
0.8
900 GeV
0.5
0.4
CMS 900 GeV
Tune Z1
data corrected
pyZ1 generator level
CMS 7 TeV
1.0
CDF 1.96 TeV
0.5
CMS 900 GeV
Tune Z1
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
Charged Particles (PT>0.5 GeV/c)
0.0
00
10
20
20
30
40
40
50
60
60
70
80
80
90
100
100
0
50
PT(chgjet#1)
GeV/c
PT(chgjet#1
or jet#1)
GeV/c
100
150
200
250
300
PT(chgjet#1 or jet#1) GeV/c
 CMS data at 900 GeV on the “transverse”
 CDF data at 1.96 TeV on the “transverse”
charged particle density, dN/dhdf, as
charged particle density, dN/dhdf, as
defined by the leading charged particle jet
defined by the leading calorimeter jet (jet#1)
(chgjet#1) for charged particles with pT >
for charged particles with pT > 0.5 GeV/c
0.5 GeV/c and |h| < 2.0. The data are
and |h| < 1.0. The data are corrected and
corrected and compared with PYTHIA Tune
compared with PYTHIA Tune Z1 at the
Z1 at the generator level.
generator level.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 14
PYTHIA Tune Z1
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.2
1.5
RDF Preliminary
data corrected
pyZ1 generator level
Charged Particle Density
Charged Particle Density
RDF Preliminary
CMS 7 TeV
1.0
CDF 1.96 TeV
0.5
CMS 900 GeV
Tune Z1
0.8
CDF 1.96 TeV
0.4
Tune Z1
0
Overall amazingly good agreement
0.0
20
40
60
100 and Tevatron
with80the LHC
0
20
40
60
80
PT(chgjet#1 or jet#1) GeV/c
Jet production and Drell-Yan! PT(lepton-pair) GeV/c
"Transverse" Charged Particle Density:(although
dN/dhdf
not perfect "Away"
yet) Charged Particle Density: dN/dhdf
100
3.0
1.6
7 TeV
data corrected
pyZ1 generator level
1.2
RDF Preliminary
What about Min-Bias?
Chgjet Production
Charged Particle Density
CMS Preliminary
Charged Particle Density
Charged Particles (PT>0.5 GeV/c)
Drell-Yan Production
Charged Particles (PT>0.5 GeV/c)
0.0
CMS 7 TeV
data corrected
pyZ1 generator level
0.8
Drell-Yan Production
0.4
Tune Z1
data corrected
pyZ1 generator level
CDF 1.96 TeV
2.0
CMS 7 TeV
1.0
Tune Z1
Drell-Yan Production
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
0
10
20
30
40
50
60
70
80
90
100
0
40
60
80
100
PT(lepton-pair) GeV/c
PT(chgjet#1) or PT(lepton-pair) GeV/c
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
20
Rick Field – Florida/CDF/CMS
Page 15
The Inelastic Non-Diffractive
Cross-Section
Occasionally one of
the parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
Proton
Majority of “minbias” events!
Proton
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
+
Proton
+
Proton
Proton
Proton
+
Proton
Proton
+…
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 16
The “Underlying Event”
Select inelastic non-diffractive events
that contain a hard scattering
Proton
Hard parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
1/(pT)4→ 1/(pT2+pT02)2
The “underlying-event” (UE)!
Proton
Given that you have one hard
scattering it is more probable to
have MPI! Hence, the UE has
more activity than “min-bias”.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 17
Allow leading hard
scattering to go to
zero pT with same
cut-off as the MPI!
Model of sND
Proton
Proton
Proton
Proton
Proton
+
Proton
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
1/(pT)4→ 1/(pT2+pT02)2
Model of the inelastic nondiffractive cross section!
+
Proton
Proton
Proton
+
Proton
Proton
+…
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 18
UE Tunes
Allow primary hard-scattering to
go to pT = 0 with same cut-off!
“Underlying Event”
Fit the “underlying
event” in a hard
scattering process.
Proton
Proton
1/(pT)4→ 1/(pT2+pT02)2
“Min-Bias”
“Min-Bias” (add
(ND)single & double diffraction)
Proton
Predict MB (ND)!
Proton
+
+
Proton
Proton
Proton
Single Diffraction
Predict MB (IN)!
+…
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Proton
+
Proton
Proton
Double Diffraction
M2
M
Rick Field – Florida/CDF/CMS
M1
Page 19
Min-Bias Collisions
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
6
CMS Data
ALICE Data
PYTHIA Tune Z1
PYTHIA Tune Z1
Charged Particle Density
Charged Particle Density
8
6
NSD = ND + DD
4
Tune Z1
CMS
2
pyZ1 ND = dashed
pyZ1 NSD = solid
7 TeV
NSD (all pT)
4
2
Tune Z1
INEL (all pT)
0
ALICE
INEL = NSD + SD
pyZ1 NSD = dashed
pyZ1 INEL = solid
900 GeV
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
Pseudo-Rapidity h
-2
-1
0
1
2
3
Pseudo-Rapidity h
 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 h, (1/NNSD) dN/dh.
 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 h, (1/NINEL) dN/dh.
“Minimum Bias” Collisions
Okay not perfect, but remember
Proton
we know that SD and DD are not modeled well!
Proton
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 20
4
MB versus UE
Divide be 2
Charged Particle Density: dN/dhdf
Charged Particle Density: dN/dh
2.5
CMS Data
CMS Data
PYTHIA Tune Z1
PYTHIA Tune Z1
Charged Particle Density
Charged Particle Density
8
6
NSD = ND + DD
4
Tune Z1
CMS
2
pyZ1 ND = dashed
pyZ1 NSD = solid
7 TeV
NSD (all pT)
2.0
1.5
1.0
0.5
pyZ1 ND = dashed
7 TeV
NSD (all pT)
pyZ1 NSD = solid
0.0
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-2
-1
0
1
2
3
4
Pseudo-Rapidity h
Pseudo-Rapidity h
 CMS NSD data on the charged particle
 CMS NSD data on the charged particle rapidity
rapidity distribution at 7 TeV compared
distribution at 7 TeV compared with PYTHIA
with PYTHIA Tune Z1. The plot shows
Tune Z1. The plot shows the average number of
the average number of charged particles
charged particles per NSD collision per unit h-f,
per NSD collision per unit h, (1/NNSD)
(1/NNSD) dN/dhdf.
dN/dh.
“Minimum Bias” Collisions
Proton
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Proton
Rick Field – Florida/CDF/CMS
Page 21
MB versus UE
Charged Particle Density: dN/dhdf
Transverse Charged Particle Density: dN/dhdf
2.5
RDF Preliminary
CMS Data
PYTHIA Tune Z1
PYTHIA Tune Z1
Charged Particle Density
Charged Particle Density
2.5
2.0
Factor of 2!
1.5
1.0
Charged Particles (|h| < 2, all pT)
0.5
Tune Z1
CMS
2.0
Tune Z1
NSD = ND + DD
1.5
1.0
0.5
7 TeV ND
pyZ1 ND = dashed
7 TeV
NSD (all pT)
pyZ1 NSD = solid
0.0
0.0
0
5
10
15
20
25
-4
-3
-2
-1
0
1
2
3
Pseudo-Rapidity h
PT max (GeV/c)
 Shows the density of charged particles in
the “transverse” region as a function of
PTmax for charged particles (All pT, |h| <
2) at 7 TeV from PYTHIA Tune Z1.
Outgoing Parton
 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 h-f,
(1/NNSD) dN/dhdf.
“Minimum Bias” Collisions
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Outgoing Parton
Proton
Underlying Event
Proton
Final-State
Radiation
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
4
Rick Field – Florida/CDF/CMS
Page 22
MB versus UE
Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
2.5
CMS Data
ATLAS
2.0
Charged Particle Density
"Transverse" Charged Density
2.5
Factor of 2!
1.5
RDF Preliminary
1.0
ATLAS corrected data
Tune Z1 generator level
0.5
7 TeV
Charged Particles (pT > 0.1 GeV/c, |h|<2.5)
CMS
PYTHIA Tune Z1
2.0
Tune Z1
1.0
0.5
pyZ1 ND = dashed
7 TeV
NSD (all pT)
0.0
NSD = ND + DD
1.5
pyZ1 NSD = solid
0.0
0
2
4
6
8
10
12
14
16
18
20
-4
-3
PTmax (GeV/c)
-2
-1
0
1
2
3
Pseudo-Rapidity h
 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, |h| < 2.5) at 7 TeV
compared with PYTHIA Tune Z1.
Outgoing Parton
 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 h-f,
(1/NNSD) dN/dhdf.
“Minimum Bias” Collisions
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Outgoing Parton
Proton
Underlying Event
Proton
Final-State
Radiation
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
4
Rick Field – Florida/CDF/CMS
Page 23
NSD Multiplicity Distribution
Charged Multiplicity Distribution
1.0E-01
RDF Preliminary
data CMS NSD
pyZ1 generator level
Difficult to produce
enough events with
large multiplicity!
CMS
Probability
1.0E-02
7 TeV
900 GeV
1.0E-03
Charged Particles
(all PT, |h|<2.0)
Tune Z1
1.0E-04
0
20
40
60
80
100
Number of Charged Particles
 Generator level charged multiplicity distribution (all pT, |h| < 2) at 900 GeV and 7
TeV. Shows the NSD = HC + DD prediction for Tune Z1. Also shows the CMS
NSD data.
“Minumum Bias” Collisions
Proton
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Okay not perfect!
But not that bad!
Rick Field – Florida/CDF/CMS
Proton
Page 24
MB & UE
"Transverse" Charged Particle Multiplicity
Charged Multiplicity Distribution
1.0E+00
1.0E-01
“Min-Bias”
RDF Preliminary
“Underlying Event”
data CMS NSD
pyZ1 generator level
Data Corrected
Tune Z1 generator level
1.0E-01
CMS
PT(chgjet#1) > 3 GeV/c
Probability
Probability
1.0E-02
7 TeV
900 GeV
1.0E-03
1.0E-02
900 GeV
1.0E-04
0
20
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-05
100
 Generator level charged multiplicity
distribution (all pT, |h| < 2) at 900 GeV
and 7 TeV. Shows the NSD = HC + DD
prediction for Tune Z1. Also shows the
CMS NSD data.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
CMS
Tune Z1
Tune Z1
Difficult to produce
40
60
80
enough
events
with
Number of Charged Particles
large multiplicity!
7 TeV
1.0E-03
1.0E-04
Charged Particles
(all PT, |h|<2.0)
CMS Preliminary
0
5
10
15
20
25
30
35
Number of Charged Particles
Difficult to produce
 CMS corrected data at 900 GeV and 7 TeV
enough events with
on the charged particle multiplicity
large “transverse”
distribution in the “transverse” region for
multiplicity at low
charged particles (pT > 0.5 GeV/c, |h| < 2)
hard scale!
as defined by the leading charged particle
jet with PT(chgjet#1) > 3 GeV/c compared
with PYTHIA Tune Z1 at the generator
level.
Rick Field – Florida/CDF/CMS
Page 25
Pile-Up at the LHC
Tune DWT “Hard-Core” No
Trigger (ct =10mm)
Charged Particle Multiplicity Distribution
Charged Particle PseuoRapidity Distribution
4
Generator Level
HCMB 14 TeV
0.04
Charged Particles (|h|<2.0, all pT)
Mean = 24.39
0.03
Generator Level
HCMB 14 TeV
pyDWT <Nchg> = 81.7
<Nchg> in 0.4 bin
Probability per 1 Particle
0.05
pyDWT <Nchg> = 24.39
0.02
Npile = 1
3
2
1
0.01
Charged Particles (all pT)
0
0.00
0
10
20
30
40
50
60
70
80
90
100
-8
-6
-2
0
2
4
6
8
PseudoRapidity h
Number of Charged Particles: Nchg
 Shows the charged multiplicity distribution
(|h| < 2, all pT) for Npile = 1 (i.e. shows, on the
average, what one event looks like). The plot
shows the probability of finding 0, 1, 2, … etc.
charged particles. The sum of the points is
equal to one. The mean is 24.39 charged
particles and s = 19.7.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
-4
 Shows the charged particle pseudo-rapidity
distribution (all pT) for Npile = 1 (i.e. shows,
on the average, what one event looks like).
The plot shows the <Nchg> in a 0.4 bin (i.e.
not divided by bin size). The sum of the
points with |h| < 2 is 24.39.
Rick Field – Florida/CDF/CMS
Page 26
Pile-Up at the LHC
Charged Particle Multiplicity Distribution
“Central Limit Theorem”:
<Nchg> ~ Npile, s ~ sqrt(Npile)!
Charged Particle Multiplicity Distribution
0.16
Generator Level
HCMB 14 TeV
Duh!
0.06
Charged Particles (|h|<2.0, all pT)
pyDWT <Nchg> = 243.9
Mean = 243.9
0.04
Npile = 1 with Nchg->10*Nchg
Npile = 10
0.02
0.00
Probability per 50 Particles
Probability per 10 Particles
0.08
Generator Level
HCMB 14 TeV
0.12
True
for any
P(|h|<2.0,
cut!
Charged
Particles
all pT)
T(min)
pyDWT <Nchg> = 1219.5
0.08
Npile = 10 with Nchg->5*Nchg
Npile = 1 with Nchg->50*Nchg
0.04
Npile = 50
0.00
0
100
200
300
400
500
600
700
800
900
1000
0
500
Number of Charged Particles: Nchg
1000
1500
2000
2500
3000
3500
4000
4500
5000
Number of Charged Particles: Nchg
 Shows the charged multiplicity distribution  Shows the charged multiplicity distribution
(|h| < 2, all pT) for Npile = 50 (i.e. shows, on
(|h| < 2, all pT) for Npile = 10 (i.e. shows, on
the average, what 50 events looks like). The
the average, what 10 events looks like). The
plot shows the probability of finding 0, 50,
plot shows the probability of finding 0, 10,
100, … etc. charged particles. The sum of the
20, … etc. charged particles. The sum of the
points is equal to one. The mean is 1219.5
points is equal to one. The mean is 243.9
charged particles and s = 138.9. Also shown
charged particles and s = 62.3. Also shown
is the Npile = 1 distribution scaled by a factor
is the Npile = 1 distribution scaled by a
of 50 (i.e. Nchg → 50×Nchg) and the Npile =
factor of 10 (i.e. Nchg → 10×Nchg).
10 distribution scaled by a factor of 5 (i.e.
Nchg → 5×Nchg).
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 27
Tevatron Energy Scan
Proton
CDF
1 mile
AntiProton
Proton
900GeV
GeV
300
1.96
TeV
AntiProton
 Just before the shutdown of the Tevatron CDF
has collected more than 10M “min-bias” events
at several center-of-mass energies!
300 GeV 12.1M MB Events
900 GeV 54.3M MB Events
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 28
New CDF Energies
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged
Charged Density
"Transverse"
1.2
7 TeV ATLAS
ATLAS
RDF Preliminary
Tune Z1 generator level
0.8
1.96 TeV CDF
900 GeV ATLAS 900 GeV CDF
0.4
300 GeV CDF
Tune Z1
Charged
Charged Particles
Particles (|h|<0.8,
(|h|<0.8, PT>0.5
PT>0.5 GeV/c)
GeV/c)
0.0
0
5
10
15
20
25
25
30
30
35
35
PTmax (GeV/c)
 ATLAS preliminary data at 900 GeV and 7 TeV on the “transverse” charged particle
density, dN/dhdf, as defined by the leading charged particle (PTmax) for charged particles
with pT > 0.5 GeV/c and |h| < 0.8. The data are corrected and compared with PYTHIA
Tune Z1 at the generator level.
 Predictions for CDF on the “transverse” charged particle density, dN/dhdf, as
defined by the leading charged particle (PTmax) for charged particles with pT > 0.5
GeV/c and |h| < 0.8 from PYTHIA Tune Z1 at the generator level.
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 29
gmbsar
Files = 273 Events = 66,374,130
Size = 803,837,367 KB
1.96 TeV
1 and only 1 Q12 Vertex
P0-5 19,420,876 Events
900 GeV
0 or 1 Q12 Vertex
38,306,169 Events
"Transverse" Charged Particle Density: dN/dhdf
PTmax Direction
Df
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Density
1.0
CDF Preliminary
Raw Data
1.96 TeV
900 GeV
0.5
300 GeV
Bin Center
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
5
10
15
20
25
30
35
PTmax (GeV/c)
 Raw CDF data at 300 GeV, 900 GeV, and 1.96 TeV on the
“transverse” charged particle density, dN/dhdf, as defined
by the leading charged particle (PTmax) for charged
particles with pT > 0.5 GeV/c and |h| < 1.0.
300 GeV
0 or 1 Q12 Vertex
7,484,514 Events
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Page 30
How Universal are the Tunes?
 Do we need a separate tune for each center-of-mass energy?
Outgoing Parton
PT(hard)
900 GeV, 1.96 TeV, 7 TeV, etc.
Initial-State Radiation
Proton
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! Tune Z1 also very good!
Proton
Underlying Event
Underlying Event
Outgoing Parton
What we are learning should
Soon we will have UE data at 300
GeV, 900
GeV,
1.96 TeV,
7
allow
for
more
precise
TeV, & 8 TeV and can map out the energy dependence!
predictions at future LHC energies
 Do we need a separate tune for each
hard
QCD13 TeV)!
(10
TeV,
Final-State
Radiation
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
Color
subprocess? Jet Production, Drell-Yan Production, etc.
The same tune can describe both Jet Production and Drell-Yan!
 Do we need separate tunes for “Min-Bias” (MB) and the
Proton
Connections
“Minimum Bias” Collisions
Proton
“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!
CMS High Luminosity Workshop
Alushta, Ukraine, May 29, 2012
Rick Field – Florida/CDF/CMS
Diffraction
Page 31