Early LHC Physics
QCD at the LHC: Findings & Surprises
Rick Field
University of Florida
Outline of Talk
 How well did we do at predicting the behavior of the
“underlying event” at 900 GeV and 7 TeV? A careful
look.
University of FloridaOutgoing
November
2010
Parton
 How well did we do at predicting the behavior of
“min-bias” collisions at 900 GeV and 7 TeV? A
careful look.
 PYTHIA 6.4 Tune Z1: New CMS 6.4 tune (pT-
“Minimum Bias” Collisions
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Underlying Event
ordered parton showers and new MPI).
Outgoing Parton
Final-State
Radiation
 New Physics in Min-Bias?? Observation of long-range
same-side correlations at 7 TeV.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
UE&MB@CMS
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!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 2
MPI, Pile-Up, and Overlap
MPI: Multiple Parton Interactions
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Underlying Event
Outgoing Parton
Pile-Up
 MPI: Additional 2-to-2 parton-parton
scatterings within a single hadron-hadron
collision.
Final-State
Radiation
Proton
Pile-Up
Proton
Proton
Proton
Primary
Interaction Region Dz
 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 hadronhadron collision from the current beam crossing because the next
crossing happened before the event could be read out.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
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”.
 All three regions have the same area in h-f space, Dh×Df = 2hcut×120o = 2hcut×2/3. Construct
densities by dividing by the area in h-f space.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 4
CMS UE Analyses
Traditional Approach
Now published in EPJC!
 Uncorrected data on the “transverse”
region as defined by the leading track,
PTmax, and the leading charged particle
jet, PT(chgjet#1) at 900 GeV (pT > 0.5
GeV/c, |h| < 2.0) compared with several
QCD Monte-Carlo models after detector
simulation.
 Uncorrected data on the “transverse”
region as defined by the leading charged
particle jet, PT(chgjet#1) at 7 TeV and 900
GeV (pT > 0.5 GeV/c, |h| < 2.0) compared
with several QCD Monte-Carlo models
after detector simulation.
UE&MB@CMS
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 5
CMS UE Analyses
New Approach
Method proposed by Gavin Salam et. al.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 6
ATLAS UE Analysis
 Corrected data on the “towards”, “away”,
and “transverse” regions as defined by the
leading track, PTmax, at 7 TeV and 900 GeV
(pT > 0.5 GeV/c, |h| < 2.5) compared with
several QCD Monte-Carlo models at the
generator level.
Traditional Approach
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 7
“Transverse” Charged Particle Density
PT(chgjet#1) Direction
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Density
0.8
Df
RDF Preliminary
Fake Data
pyDW generator level
ChgJet#1
“Toward”
0.6
PTmax
“Transverse”
“Transverse”
0.4
Leading Charged
Particle Jet, chgjet#1.
“Away”
0.2
900 GeV
Prediction!
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
PTmax Direction
0.0
0
2
4
6
8
10
12
14
16
PTmax or PT(chgjet#1) (GeV/c)
“Toward”
 Fake data (from MC) at 900 GeV on the
“transverse” charged particle density,
dN/dhdf, 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 |h| < 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).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Df
18
Rick Field – Florida/CDF/CMS
“Transverse”
“Transverse”
Leading Charged
Particle, PTmax.
“Away”
Rick Field
MB&UE@CMS Workshop
CERN, November 6, 2009
Page 8
“Transverse” Charged Particle Density
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
RDF Preliminary
Fake Data
pyDW generator level
"Transverse" Charged Density
"Transverse" Charged Density
0.8
ChgJet#1
0.6
PTmax
0.4
0.2
900 GeV
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.8
CMS Preliminary
ChgJet#1
data uncorrected
pyDW + SIM
0.6
PTmax
0.4
0.2
900 GeV
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
0
2
6
8
10
12
14
16
18
PTmax or PT(chgjet#1) (GeV/c)
PTmax or PT(chgjet#1) (GeV/c)
 Fake data (from MC) at 900 GeV on the
“transverse” charged particle density,
dN/dhdf, 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 |h| < 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).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
4
 CMS preliminary data at 900 GeV on the
“transverse” charged particle density,
dN/dhdf, 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 |h| < 2. The data are
uncorrected and compared with PYTHIA
Tune DW after detector simulation (216,215
events in the plot).
Rick Field – Florida/CDF/CMS
Page 9
“Transverse” Charged PTsum Density
"Transverse" Charged PTsum Density: dPT/dhdf
"Transverse" Charged PTsum Density: dPT/dhdf
0.8
0.8
ChgJet#1
Fake Data
pyDW generator level
0.6
PTsum Density (GeV/c)
PTsum Density (GeV/c)
RDF Preliminary
PTmax
0.4
0.2
900 GeV
CMS Preliminary
data uncorrected
pyDW + SIM
0.6
ChgJet#1
PTmax
0.4
0.2
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
2
4
6
8
10
12
14
16
18
0
2
4
6
8
10
12
14
16
18
PTmax or PT(chgjet#1) (GeV/c)
PTmax or PT(chgjet#1) (GeV/c)
 Fake data (from MC) at 900 GeV on the
 CMS preliminary data at 900 GeV on the
“transverse” charged PTsum density,
“transverse” charged PTsum density,
dPT/dhdf, as defined by the leading charged
dPT/dhdf, as defined by the leading charged
particle (PTmax) and the leading charged
particle (PTmax) and the leading charged
particle jet (chgjet#1) for charged particles
particle jet (chgjet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 2. The fake
with pT > 0.5 GeV/c and |h| < 2. The data are
data (from PYTHIA Tune DW) are generated
uncorrected and compared with PYTHIA
at the particle level (i.e. generator level)
Tune DW after detector simulation (216,215
assuming 0.5 M min-bias events at 900 GeV
events in the plot).
(361,595 events in the plot).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 10
PYTHIA Tune DW
"Transverse" Charged Particle Density: dN/dhdf
1.2
PT(chgjet#1) Direction
Charged Particle Density
CMS Preliminary
Df
7 TeV
data uncorrected
pyDW + SIM
0.8
“Toward”
“Transverse”
900 GeV
“Transverse”
0.4
“Away”
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
5
10
15
20
25
30
35
40
45
50
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. The data are
uncorrected and compared with PYTHIA Tune
DW after detector simulation.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 11
PYTHIA Tune DW
PTmax Direction
Df
“Toward”
“Transverse”
“Transverse”
“Away”
"Transverse" Charged Density
"Transverse" Charged Particle Density: dN/dhdf
1.2
RDF Preliminary
7 TeV
ATLAS corrected data
Tune DW generator level
0.8
900 GeV
0.4
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
20
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| < 2.5. The data are corrected
and compared with PYTHIA Tune DW at the
generator level.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 12
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
50
0
2
4
6
8
10
12
14
16
18
20
PTmax (GeV/c)
PT(chgjet#1) GeV/c
 CMS preliminary data at 900 GeV and 7 TeV  ATLAS preliminary data at 900 GeV and 7 TeV
on the “transverse” charged particle density,
on the “transverse” charged particle density,
dN/dhdf, as defined by the leading charged
dN/dhdf, as defined by the leading charged
particle jet (chgjet#1) for charged particles with particle (PTmax) for charged particles with pT >
0.5 GeV/c and |h| < 2.5. The data are corrected
pT > 0.5 GeV/c and |h| < 2. The data are
uncorrected and compared with PYTHIA Tune and compared with PYTHIA Tune DW at the
generator level.
DW after detector simulation.
PT(chgjet#1) Direction
PTmax Direction
Df
Df
“Toward”
“Transverse”
“Toward”
“Transverse”
“Transverse”
“Away”
UF-IFT Seminar
Gainesville, FL, November 19, 2010
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 13
PYTHIA Tune DW
"Transverse" Charged PTsum Density: dPT/dhdf
1.5
CMS Preliminary
RDF Preliminary
7 TeV
data uncorrected
pyDW + SIM
1.2
PTsum Density (GeV/c)
Charged PTsum Density (GeV/c)
"Transverse" Charged PTsum Density: dPT/dhdf
1.6
CMS
0.8
900 GeV
0.4
7 TeV
ATLAS corrected data
Tune DW generator level
1.0
ATLAS
900 GeV
0.5
Charged Particles (|h|<2.5, 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
 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. The data are
uncorrected and compared with PYTHIA
Tune DW after detector simulation.
Df
10
12
14
16
18
“Toward”
“Transverse”
“Transverse”
“Away”
UF-IFT Seminar
Gainesville, FL, November 19, 2010
8
 ATLAS preliminary 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 DW at the
generator level. PTmax DirectionDf
“Toward”
“Transverse”
6
PTmax (GeV/c)
PT(chgjet#1) (GeV/c)
PT(chgjet#1) Direction
4
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 14
20
“Transverse” Charge Density
"Transverse" Charged Particle Density: dN/dhdf
Rick Field
MB&UE@CMS Workshop
CERN, November 6, 2009
"Transverse" Charged Density
1.2
RDF Preliminary
py Tune DW generator level
7 TeV
0.8
factor of 2!
900 GeV
0.4
Prediction!
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
4
10
0.0
0
2
6
8
12
14
16
18
20
PTmax (GeV/c)
PTmax Direction
Df
LHC
900 GeV
“Toward”
“Transverse”
PTmax Direction
900 GeV → 7 TeV
(UE increase ~ factor of 2)
“Transverse”
“Away”
~0.4 → ~0.8
Df
“Toward”
LHC
7 TeV
“Transverse”
“Transverse”
“Away”
 Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, |h| < 2) at 900 GeV and 7 TeV as defined by PTmax from PYTHIA Tune DW and at the
particle level (i.e. generator level).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 15
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
on the “transverse” charged particle density,
particle density, dN/dhdf, as defined by the
dN/dhdf, as defined by the leading charged
particle jet (chgjet#1) for charged particles with leading charged particle jet (chgjet#1) for
charged particles with pT > 0.5 GeV/c and |h|
pT > 0.5 GeV/c and |h| < 2. The data are
< 2. The data are uncorrected and compared
uncorrected and compared with PYTHIA Tune
with PYTHIA Tune DW after detector
DW after detector simulation.
PT(chgjet#1) Direction
simulation. PT(chgjet#1) Direction
Df
Df
“Toward”
“Transverse”
“Toward”
“Transverse”
“Transverse”
“Away”
UF-IFT Seminar
Gainesville, FL, November 19, 2010
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 16
PYTHIA Tune DW
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
3.0
3.0
RDF Preliminary
data uncorrected
pyDW + SIM
Ratio: 7 TeV/900 GeV
Ratio: 7 TeV/900 GeV
CMS Preliminary
2.0
CMS
1.0
7 TeV / 900 GeV
ATLAS corrected data
pyDW generator level
2.0
ATLAS
1.0
7 TeV / 900 GeV
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
0
1
 Ratio of 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. The data are uncorrected and compared
with PYTHIA Tune DW after detector
simulation. PT(chgjet#1) Direction
Df
4
5
6
7
8
9
10
11
 Ratio of the 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| < 2.5. The data are corrected
and compared with PYTHIA Tune DW at
the generator level.PTmax DirectionDf
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
UF-IFT Seminar
Gainesville, FL, November 19, 2010
3
PTmax (GeV/c)
PT(chgjet#1) (GeV/c)
“Transverse”
2
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 17
12
PYTHIA Tune DW
"Transverse" Charged PTsum Density: dPT/dhdf
"Transverse" Charged PTsum Density: dPT/dhdf
4.0
3.0
CMS Preliminary
RDF Preliminary
data uncorrected
pyDW + SIM
ATLAS corrected data
pyDW generator level
Ratio: 7 TeV/900 GeV
Ratio: 7 TeV/900 GeV
4.0
2.0
CMS
1.0
3.0
2.0
ATLAS
1.0
7 TeV / 900 GeV
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
7 TeV / 900 GeV
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
0
1
 Ratio of the 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. The data are uncorrected and compared
with PYTHIA Tune DW after detector
simulation. PT(chgjet#1) Direction
Df
4
5
6
7
8
9
10
11
12
 Ratio of the ATLAS preliminary 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 DW at the generator level.
“Toward”
PTmax Direction
Df
“Toward”
“Transverse”
“Transverse”
“Away”
UF-IFT Seminar
Gainesville, FL, November 19, 2010
3
PTmax (GeV/c)
PT(chgjet#1) (GeV/c)
“Transverse”
2
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 18
“Transverse” Multiplicity Distribution
"Transverse" Charged Particle Multiplicity
Same hard scale at
two different centerof-mass energies!
1.0E+00
PT(chgjet#1) > 3 GeV/c
1.0E-01
CMS Preliminary
data uncorrected
pyDW + SIM
Probability
1.0E-02
CMS
1.0E-03
PT(chgjet#1) Direction
Df
7 TeV
900 GeV
1.0E-04
“Toward”
1.0E-05
Normalized to 1
“Transverse”
1.0E-06
“Transverse”
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-07
“Away”
0
5
10
15
20
25
30
35
40
Number of Charged Particles
 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, |h| < 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).
Shows the growth of the
“underlying event” as the center-of-mass energy increases.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 19
“Transverse” Multiplicity Distribution
Same center-of-mass
energy at two different
hard scales!
"Transverse" Charged Particle Multiplicity
1.0E+00
7 TeV
CMS Preliminary
1.0E-01
data uncorrected
pyDW + SIM
Probability
1.0E-02
PT(chgjet#1) > 20 GeV/c
1.0E-03
PT(chgjet#1) Direction
1.0E-04
Df
PT(chgjet#1) > 3 GeV/c
1.0E-05
CMS
Normalized to 1
1.0E-06
“Toward”
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
“Transverse”
“Transverse”
1.0E-07
0
5
10
15
20
25
30
35
40
“Away”
Number of Charged Particles
 CMS uncorrected data at 7 TeV on the charged particle multiplicity distribution in the
“transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 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).
Shows the growth of the
“underlying event” as the hard scale increases.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 20
PYTHIA Tune DW
How well did we do at predicting the “underlying event” at 900 GeV and 7 TeV?
"Transverse" Charged Particle Density: dN/dhdf
1.2
CMS Preliminary
CMS Preliminary
ChgJet#1
data uncorrected
pyDW + SIM
0.6
Charged Particle Density
"Transverse" Charged Density
"Transverse" Charged Particle Density: dN/dhdf
0.8
PTmax
0.4
0.2
900 GeV
Tune DW
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
7 TeV
data uncorrected
pyDW + SIM
0.8
900 GeV
0.4
Tune DW
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
0
5
10
15
20
PTmax or PT(chgjet#1) (GeV/c)
25
30
35
40
45
50
PT(chgjet#1) GeV/c
"Transverse" Charged Particle Density: dN/dhdf
3.0
CMS Preliminary
Ratio: 7 TeV/900 GeV
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!
Tune DW
data uncorrected
pyDW + SIM
2.0
1.0
7 TeV / 900 GeV
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
PT(chgjet#1) (GeV/c)
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 21
PYTHIA Tune DW
How well did we do at predicting the “underlying event” at 900 GeV and 7 TeV?
"Transverse" Charged Particle Density: dN/dhdf
1.2
CMS Preliminary
CMS Preliminary
ChgJet#1
data uncorrected
pyDW + SIM
0.6
Charged Particle Density
"Transverse" Charged Density
"Transverse" Charged Particle Density: dN/dhdf
0.8
PTmax
0.4
0.2
900 GeV
Tune DW
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
7 TeV
data uncorrected
pyDW + SIM
0.8
900 GeV
0.4
Tune DW
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
0
5
10
15
20
PTmax or PT(chgjet#1) (GeV/c)
25
30
35
40
45
50
PT(chgjet#1) GeV/c
"Transverse" Charged Particle Density: dN/dhdf
3.0
CMS Preliminary
Ratio: 7 TeV/900 GeV
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!
Tune DW
data uncorrected
pyDW + SIM
2.0
1.0
7 TeV / 900 GeV
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
PT(chgjet#1) (GeV/c)
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 22
UE Summary
 The “underlying event” at 7 TeV and
900 GeV is almost what we expected!
With a little tuning we should be able
to describe the data very well (see
Tune Z1 later in this talk).
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Underlying Event
Warning! All the UE studies look
Parton
at charged particles with pT > 0.5Outgoing
GeV/c.
I am surprised thatWe
thedoTunes
did as well as
not know if the models correctly
they did at predictingdescribe
the behavior
the pT values!
the UE atof
lower
“underlying event” at 900 GeV and 7 TeV!
Remember this is “soft” QCD!
“Min-Bias” is a whole different story!
Much more complicated due to very
soft particles and diffraction!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Final-State
Radiation
PARP(82)
PARP(90)
Color
Diffraction
Connections
Page 23
Rick Field University of Chicago
July 11, 2006
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“Toward”
“TransMAX”
“TransMIN”
“Away”
Neither PY Tune A or
“Toward”
HERWIG fits the
ETsum
density in the
“TransMAX”
“TransMIN”
“transferse” region!
HERWIG
does slightly
“Away”
better than Tune A!
"Transverse" ETsum Density (GeV)
Df
Df
"TransMAX" ETsum Density: dET/dhdf
7.0
Jet #2 Direction
CDF Run 2 Preliminary
6.0
"Leading Jet"
1.96 TeV
5.0
4.0
3.0
HW
"Back-to-Back"
2.0
1.0
PY Tune A
MidPoint R = 0.7 |h(jet#1) < 2
Particles (|h|<1.0, all PT)
0.0
 Shows the data on the tower ETsum
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
"TransMIN" ETsum Density: dET/dhdf
3.0
"Transverse" ETsum Density (GeV)
density, dETsum/dhdf, in the “transMAX”
and “transMIN” region (ET > 100 MeV, |h|
< 1) versus PT(jet#1) for “Leading Jet”
and “Back-to-Back” events.
 Compares the (corrected) data with
PYTHIA Tune A (with MPI) and
HERWIG (without MPI) at the particle
level (all particles, |h| < 1).
data corrected to particle level
CDF Run 2 Preliminary
MidPoint R = 0.7 |h(jet#1) < 2
data corrected to particle level
2.5
Particles (|h|<1.0, all PT)
1.96 TeV
2.0
HW
"Leading Jet"
1.5
1.0
0.5
"Back-to-Back"
PY Tune A
0.0
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 24
Rick Field University of Chicago
July 11, 2006
Possible Scenario??
 PYTHIA Tune A fits the charged particle
"Transverse" pT Distribution: dN/dpT
1.0E+01
"Transverse" PT Distribution
Sharp Rise at
Low PT?
PTsum density for pT > 0.5 GeV/c, but it
does not produce enough ETsum for
towers with ET > 0.1 GeV.
Possible Scenario??
But I cannot get any
of the Monte-Carlo to
do this perfectly!
1.0E+00
1.0E-01
 It is possible that there is a sharp rise in
Multiple
Parton
Interactions
the number of particles in the “underlying
event” at low pT (i.e. pT < 0.5 GeV/c).
1.0E-02
Beam-Beam
Remnants
1.0E-03
 Perhaps there are two components, a vary
1.0E-04
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
pT All Particles (GeV/c)
UF-IFT Seminar
Gainesville, FL, November 19, 2010
4.0
4.5
5.0
“soft” beam-beam remnant component
(Gaussian or exponential) and a “hard”
multiple interaction component.
Rick Field – Florida/CDF/CMS
Page 25
Proton-Proton Collisions
Elastic Scattering
Single Diffraction
Double Diffraction
M2
M
M1
stot = sEL + sSD
IN +sDD +sHC
ND
“Inelastic Non-Diffractive Component”
Hard Core
The “hard core” component
contains both “hard” and
“soft” collisions.
“Hard” Hard Core (hard scattering)
Outgoing Parton
“Soft” Hard Core (no hard scattering)
Proton
PT(hard)
Proton
Proton
Proton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 26
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
+…
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 27
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”.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 28
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
+…
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 29
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
All of Rick’s tunes (except X2):
1/(pT)4→ 1/(pT2+pT02)2
A, AW, AWT,DW, DWT,
D6, D6T, CW, X1,
“Min-Bias”
“Min-Bias” (add
(ND)single & double diffraction)
and Tune Z1,
are UE tunes!
Proton
Predict MB (ND)!
Proton
+
+
Proton
Proton
Proton
Single Diffraction
Predict MB (IN)!
+…
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Proton
+
Proton
Proton
Double Diffraction
M2
M
Rick Field – Florida/CDF/CMS
M1
Page 30
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
1.0E+00
CDF Run 2 Preliminary
1.0E-01
CDF Run 2 <Nchg>=4.5
CDF Run 2 <Nchg>=4.5
1.0E-02
Probability
Probability
1.0E-02
CDF Run 2 Preliminary
1.0E-01
1.0E-03
1.0E-04
1.0E-05
py Tune A <Nchg> = 4.3
pyAnoMPI <Nchg> = 2.6
1.0E-03
1.0E-04
1.0E-05
1.0E-06
1.0E-06
Min-Bias 1.96
1.0E-07
Min-Bias 1.96
1.0E-07
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
Normalized to 1
Normalized to 1
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
1.0E-08
1.0E-08
0
5
10
15
20
25
30
35
40
45
50
55
0
5
10
Number of Charged Particles
i
20
25
30
35
40
45
50
Number of Charged Particles
“Minimum Bias” Collisions
Proton
15
No MPI!
Tune A!
AntiProton
 Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |h| < 1) for “min-bias”
collisions at CDF Run 2 (non-diffractive cross-section).
 The data are compared with PYTHIA Tune A and Tune A without multiple parton
interactions (pyAnoMPI).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 31
55
PYTHIA Tune A Min-Bias
“Soft” + ”Hard”
Charged Particle Density
1.0E+00
Pythia 6.206 Set A
CDF Min-Bias Data
Charged Density dN/dhdfdPT (1/GeV/c)
1.0E-01
Ten decades!
1.8 TeV |h|<1
1.0E-02
12% of “Min-Bias” events
have PT(hard) > 5 GeV/c!
PT(hard) > 0 GeV/c
1.0E-03
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
1.0E-04
1.0E-05
CDF Preliminary
1.0E-06
0
2
4
6
8
PT(charged) (GeV/c)
10
12
14
Lots of “hard” scattering in
“Min-Bias” at the Tevatron!
 Comparison of PYTHIA Tune A with the pT distribution of charged particles for “min-bias”
collisions at CDF Run 1 (non-diffractive cross-section).
pT = 50 GeV/c!
 PYTHIA Tune A predicts that 12% of all “Min-Bias” events are a result of a hard 2-to-2
parton-parton scattering with PT(hard) > 5 GeV/c (1% with PT(hard) > 10 GeV/c)!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 32
CDF: Charged pT Distribution
Erratum November 18, 2010
Excess
No excess
events
atat
large
large
pTp! T!
“Minimum Bias” Collisions
Proton
AntiProton
50 GeV/c!
 Published CDF data on the pT distribution
of charged particles in Min-Bias collisions
(ND) at 1.96 TeV compared with PYTHIA
Tune A.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
CDF
CDFinconsistent
consistent with
withCMS
CMSand
andUA1!
UA1!
Rick Field – Florida/CDF/CMS
Page 33
MB Tunes
“Underlying Event”
Predict the “underlying
event” in a hard
scattering process!
Proton
Proton
Most of Peter Skand’s tunes:
S320 Perugia
0, S325 Perugia X,
“Min-Bias”
(ND)
S326 Perugia 6
are MB tunes!
Proton
Fit MB (ND).
Proton
+
Proton
+
Proton
Proton
Proton
+
Proton
Proton
+…
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 34
MB+UE Tunes
“Underlying Event”
Fit the “underlying
event” in a hard
scattering process!
Proton
Proton
Most of Hendrik’s “Professor”
tunes: ProQ20, P329
are MB+UE!
Simultaneous fit
to both MB & UE
“Min-Bias” (ND)
Proton
Fit MB (ND).
Proton
+
Proton
+…
UF-IFT Seminar
Gainesville, FL, November 19, 2010
+
Proton
Proton
Proton
+
Proton
Proton
The ATLAS AMBT1 Tune is an MB+UE tune, but
because they include in the fit the ATLAS UE data
with PTmax > 10 GeV/c (big errors) the LHC UE data
does not have much pull (hence mostly an MB tune!).
Rick Field – Florida/CDF/CMS
Page 35
LHC MB Predictions: 900 GeV
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
5
5
RDF Preliminary
Charged Particle Density
Charged Particle Density
RDF Preliminary
4
3
2
ALICE INEL
Off by 11%!
UA5 INEL
INEL = HC+DD+SD
900 GeV
1
5
-1.5
-1.0
-0.5
0.0
4
Charged Particle Density
-2.0
2
UA5
ALICE
1
pyDW_10mm (3.04)
pyS320_10mm (3.09)
pyS320 INEL (2.70)
0
-2.5
3
NSD = HC+DD
Charged Particle Density: dN/dh
900 GeV
pyDW INEL (2.67)
Charged Particles (all pT)
-3.0
4
RDF Preliminary
0.5
1.0
1.5
0
2.0
2.5
3.0
-3.0
-2.5
-2.0 times
-1.5 1.11
-1.0
3
0.5
1.0
1.5
2.0
2.5
“Minimum Bias” Collisions
“Minimum Bias” Collisions
2
Proton
1
0.0
PseudoRapidity h
PseudoRapidity h
Proton
-0.5
INEL = HC+DD+SD
900 GeV
Charged Particles (all pT)
Proton
ALICE INEL
UA5 INEL
pyDW times 1.11 (2.97)
pyS320 times 1.11 (3.00)
Proton
0
-3.0 ALICE
-2.5 -2.0 -1.5
-1.0 with
-0.5 0.0
0.5
1.0
1.5
2.0 DW
2.5
3.0and Tune S320
 Compares the 900 GeV
data
PYTHIA
Tune
PseudoRapidity
h
Perugia 0. Tune DW uses the old Q2-ordered parton shower and the old MPI
model. Tune S320 uses the new pT-ordered parton shower and the new MPI model.
The numbers in parentheses are the average value of dN/dh for the region |h| <
0.6.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 36
3.0
ATLAS INEL dN/dh
 None of the tunes fit the
ATLAS INEL dN/dh
data with PT > 100
MeV! They all predict
too few particles.
Off by 20-50%!
 The ATLAS Tune
AMBT1 was designed to
fit the inelastic data for
Nchg ≥ 6 with pT > 0.5
GeV/c!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Soft particles!
Rick Field – Florida/CDF/CMS
Page 37
PYTHIA Tune DW
If one increases the pT
the agreement
improves!
Charged Particle Density: dN/dh
5
Charged Particle Density
RDF Preliminary
4
At Least 1 Charged Particle |h| < 0.8
900 GeV
ALICE INEL data
pyDW generator level
pT > 0.15 GeV/c
Tune DW
3
pT > 0.5 GeV/c
2
pT > 1.0 GeV/c
1
0
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
PseudoRapidity h
 ALICE inelastic data at 900 GeV on the dN/dh distribution for charged particles (pT >
PTmin) for events with at least one charged particle with pT > PTmin and |h| < 0.8 for
PTmin = 0.15 GeV/c, 0.5 GeV/c, and 1.0 GeV/c compared with PYTHIA Tune DW at the
generator level.
“Minimum Bias” Collisions
ProtonThe
same thing occurs at 7 TeV!
Proton
ALICE, ATLAS, and CMS data coming soon.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 38
PYTHIA Tune DW
Diffraction
contributes less at
harder scales!
Charged Particle Density: dN/dh
5
Charged Particle Density
RDF Preliminary
4
At Least 1 Charged Particle |h| < 0.8
900 GeV
ALICE INEL data
pyDW generator level
pT > 0.15 GeV/c
3
Tune DW
pT > 0.5 GeV/c
2
pT > 1.0 GeV/c
1
dashed = ND solid = INEL
0
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
PseudoRapidity h
 ALICE inelastic data at 900 GeV on the dN/dh distribution for charged particles (pT >
PTmin) for events with at least one charged particle with pT > PTmin and |h| < 0.8 for
PTmin = 0.15 GeV/c, 0.5 GeV/c, and 1.0 GeV/c compared with PYTHIA Tune Z1 at the
generator level (dashed = ND, solid = INEL).
“Minimum Bias” Collisions
Proton
Cannot
trust PYTHIA 6.2 modeling of diffraction!
Proton
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 39
CMS dN/dh
Charged Particle Density: dN/dh
8
CMS
Charged Particle Density
7 TeV
6
4
RDF Preliminary
CMS NSD data
pyDW generator level
Tune DW
Soft particles!
Okay if the Monte-Carlo does not fit
dashedthe
= ND solid
= NSD
data
what do we do? All pT
0
We tune the Monte-Carlo
-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0
0.5
1.0
1.5
2.0
2.5
3.0
to fit the
data!
PseudoRapidity h
Be careful not to tune away new physics!
 Generator level dN/dh (all pT). Shows the NSD = HC + DD and the HC = ND
contributions for Tune DW. Also shows the CMS NSD data.
2
“Minimum Bias” Collisions
Proton
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Off by 50%!
Rick Field – Florida/CDF/CMS
Proton
Page 40
PYTHIA Tune Z1
 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)!
 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.
 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!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
PARP(90)
PARP(82)
Color
Connections
Diffraction
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
UE&MB@CMS
Page 41
PYTHIA Tune Z1
Tune Z1
(R. Field CMS)
Tune AMBT1
(ATLAS)
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
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
Parameter
Parton Distribution Function
Parameters not
shown are the
PYTHIA 6.4 defaults!
PARP(80) – Probability colored parton from BBR
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 42
PYTHIA Tune Z1
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.2
1.2
CMS Preliminary
D6T
7 TeV
data uncorrected
Theory + SIM
Charged Particle Density
Charged Particle Density
CMS Preliminary
0.8
900 GeV
DW
0.4
CMS
7 TeV
data uncorrected
pyZ1 + SIM
0.8
900 GeV
0.4
CMS
Tune Z1
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
5
10
15
20
25
30
35
40
45
50
PT(chgjet#1) GeV/c
PT(chgjet#1) GeV/c
 CMS preliminary data at 900 GeV and 7 TeV  CMS preliminary data at 900 GeV and 7 TeV
on the “transverse” charged particle density,
on the “transverse” charged particle density,
dN/dhdf, as defined by the leading charged
dN/dhdf, as defined by the leading charged
particle jet (chgjet#1) for charged particles
particle jet (chgjet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 2.0. The data
with pT > 0.5 GeV/c and |h| < 2.0. The data
are uncorrected and compared with PYTHIA
are uncorrected and compared with PYTHIA
Tune DW and D6T after detector simulation
Tune Z1 after detector simulation (SIM).
(SIM).
Color reconnection suppression.
Color reconnection strength.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Tune Z1 (CTEQ5L)
PARP(82) = 1.932
PARP(90) = 0.275
PARP(77) = 1.016
PARP(78) = 0.538
Rick Field – Florida/CDF/CMS
Tune Z1 is a PYTHIA 6.4 using
pT-ordered parton showers and
the new MPI model!
Page 43
PYTHIA Tune Z1
"Transverse" Charged PTsum Density: dPT/dhdf
CMS Preliminary
D6T
data uncorrected
Theory + SIM
1.2
Charged PTsum Density (GeV/c)
Charged PTsum Density (GeV/c)
"Transverse" Charged PTsum Density: dPT/dhdf
1.6
7 TeV
0.8
DW
900 GeV
CMS
0.4
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
5
10
15
20
25
30
35
40
45
50
1.6
CMS Preliminary
7 TeV
data uncorrected
pyZ1 + SIM
1.2
0.8
900 GeV
CMS
0.4
Tune Z1
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
5
PT(chgjet#1) (GeV/c)
10
15
20
25
30
35
40
45
50
PT(chgjet#1) (GeV/c)
 CMS preliminary data at 900 GeV and 7 TeV  CMS preliminary data at 900 GeV and 7 TeV
on the “transverse” charged PTsum density,
on the “transverse” charged PTsum density,
dPT/dhdf, as defined by the leading charged
dPT/dhdf, as defined by the leading charged
particle jet (chgjet#1) for charged particles
particle jet (chgjet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 2.0. The data
with pT > 0.5 GeV/c and |h| < 2.0. The data
are uncorrected and compared with PYTHIA
are uncorrected and compared with PYTHIA
Tune DW and D6T after detector simulation
Tune Z1 after detector simulation (SIM).
(SIM).
Color reconnection suppression.
Color reconnection strength.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Tune Z1 (CTEQ5L)
PARP(82) = 1.932
PARP(90) = 0.275
PARP(77) = 1.016
PARP(78) = 0.538
Rick Field – Florida/CDF/CMS
Tune Z1 is a PYTHIA 6.4 using
pT-ordered parton showers and
the new MPI model!
Page 44
PYTHIA Tune Z1
"Transverse" Charged PTsum Density: dPT/dhdf
1.2
1.5
RDF Preliminary
RDF Preliminary
7 TeV
ATLAS corrected data
Tune Z1 generator level
PTsum Density (GeV/c)
"Transverse" Charged Density
"Transverse" Charged Particle Density: dN/dhdf
0.8
900 GeV
0.4
ATLAS
Tune Z1
7 TeV
ATLAS corrected data
Tune Z1 generator level
1.0
900 GeV
0.5
ATLAS
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
Tune Z1
0.0
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
20
0
2
PTmax (GeV/c)
UF-IFT Seminar
Gainesville, FL, November 19, 2010
6
8
10
12
14
16
18
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| < 2.5.
The data are corrected and compared with
PYTHIA Tune Z1 at the generator level.
Color reconnection suppression.
Color reconnection strength.
4
 ATLAS preliminary 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.
Tune Z1 (CTEQ5L)
PARP(82) = 1.932
PARP(90) = 0.275
PARP(77) = 1.016
PARP(78) = 0.538
Rick Field – Florida/CDF/CMS
Tune Z1 is a PYTHIA 6.4 using
pT-ordered parton showers and
the new MPI model!
Page 45
20
PYTHIA Tune Z1
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
3.0
3.0
CMS Preliminary
DW
D6T
data uncorrected
theory + SIM
Ratio: 7 TeV/900 GeV
Ratio: 7 TeV/900 GeV
CMS Preliminary
2.0
P0
1.0
CW
CMS
7 TeV / 900 GeV
Tune Z1
data uncorrected
pyZ1 + SIM
2.0
1.0
CMS
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
2
4
6
8
10
12
14
16
18
0
2
PT(chgjet#1) (GeV/c)
6
8
10
12
14
16
18
PT(chgjet#1) (GeV/c)
 Ratio of CMS preliminary data at 900 GeV
and 7 TeV (7 TeV divided by 900 GeV) on the
“transverse” charged particle density 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
uncorrected and compared with PYTHIA
Tune DW, D6T, CW, and P0 after detector
simulation (SIM).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
4
 Ratio of CMS preliminary data at 900 GeV
and 7 TeV (7 TeV divided by 900 GeV) on the
“transverse” charged particle density 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
uncorrected and compared with PYTHIA
Tune Z1 after detector simulation (SIM).
Rick Field – Florida/CDF/CMS
Page 46
PYTHIA Tune Z1
"Transverse" Charged PTsum Density: dPT/dhdf
3.0
D6T
CMS Preliminary
CMS Preliminary
DW
data uncorrected
theory + SIM
Ratio: 7 TeV/900 GeV
Ratio: 7 TeV/900 GeV
"Transverse" Charged PTsum Density: dPT/dhdf
3.0
2.0
P0
CW
1.0
CMS
7 TeV / 900 GeV
data uncorrected
pyZ1 + SIM
Tune Z1
2.0
1.0
CMS
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
7 TeV / 900 GeV
0.0
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
0
2
PT(chgjet#1) (GeV/c)
6
8
10
12
14
16
18
PT(chgjet#1) (GeV/c)
 Ratio of CMS preliminary data at 900 GeV
and 7 TeV (7 TeV divided by 900 GeV) on the
“transverse” charged PTsum density 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
uncorrected and compared with PYTHIA
Tune DW, D6T, CW, and P0 after detector
simulation (SIM).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
4
 Ratio of CMS preliminary data at 900 GeV
and 7 TeV (7 TeV divided by 900 GeV) on the
“transverse” charged PTsum density 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
uncorrected and compared with PYTHIA
Tune Z1 after detector simulation (SIM).
Rick Field – Florida/CDF/CMS
Page 47
PYTHIA Tune Z1
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged PTsum Density: dPT/dhdf
4.0
3.0
RDF Preliminary
RDF Preliminary
ATLAS corrected data
Tune Z1 generator level
ATLAS corrected data
Tune Z1 generator level
Ratio: 7 TeV/900 GeV
Ratio: 7 TeV/900 GeV
4.0
Tune Z1
2.0
ATLAS
1.0
7 TeV / 900 GeV
3.0
Tune Z1
2.0
1.0
ATLAS
7 TeV / 900 GeV
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
0
1
2
3
4
5
6
7
8
9
10
11
12
0
1
PTmax (GeV/c)
3
4
5
6
7
8
9
10
11
12
PTmax (GeV/c)
 Ratio of the ATLAS preliminary data on the
charged particle density in the “transverse”
region for charged particles (pT > 0.5 GeV/c,
|h| < 2.5) at 900 GeV and 7 TeV as defined by
PTmax compared with PYTHIA Tune Z1 at
the generator level.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
2
 Ratio of the ATLAS preliminary data on the
charged PTsum density in the “transverse”
region for charged particles (pT > 0.5 GeV/c,
|h| < 2.5) at 900 GeV and 7 TeV as defined by
PTmax compared with PYTHIA Tune Z1 at
the generator level.
Rick Field – Florida/CDF/CMS
Page 48
“Transverse” Multiplicity Distribution
Same hard"Transverse"
scale at Charged Particle Multiplicity
1.0E+00 centertwo different
PT(chgjet#1) > 3 GeV/c
CMS Preliminary
of-mass
energies!
data uncorrected
1.0E-01
"Transverse" Charged Particle Multiplicity
1.0E+00
PT(chgjet#1) > 3 GeV/c
CMS
1.0E-02
Probability
CMS
1.0E-02
Probability
CMS Preliminary
data uncorrected
Theory + SIM
1.0E-01
1.0E-03
7 TeV
900 GeV
1.0E-04
D6T
1.0E-05
pyZ1 + SIM
Tune Z1
1.0E-03
7 TeV
900 GeV
1.0E-04
1.0E-05
DW
Normalized to 1
Normalized to 1
1.0E-06
1.0E-06
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-07
1.0E-07
0
5
10
15
20
25
30
35
40
Number of Charged Particles
0
5
10
15
20
25
30
35
40
Number of Charged Particles
Difficult to produce
 CMS uncorrected data at 900 GeV and 7 TeV on  CMS uncorrected data at 900 GeV and 7
enough events
TeV on the charged
particlewith
multiplicity
the charged particle multiplicity distribution in
large
“transverse”
the “transverse” region for charged particles (pT > distribution in the “transverse” region
multiplicity
lowGeV/c, |h|
for charged particles
(pT at
> 0.5
0.5 GeV/c, |h| < 2) as defined by the leading
hard
< 2) as defined by
the scale!
leading charged
charged particle jet with PT(chgjet#1) > 3 GeV/c
compared with PYTHIA Tune DW and Tune D6T particle jet with PT(chgjet#1) > 3 GeV/c
compared with PYTHIA Tune Z1 at the
at the detector level (i.e. Theory + SIM).
detector level (i.e. Theory + SIM).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 49
“Transverse” PTsum Distribution
Same hard
scale at
"Transverse"
Charged PTsum Distribution
1.0E+00
two different
centerCMS Preliminary
PT(chgjet#1) > 3 GeV/c
data uncorrected
of-mass energies!
"Transverse" Charged PTsum Distribution
1.0E+00
CMS Preliminary
1.0E-01
data uncorrected
Theory + SIM
1.0E-02
CMS
7 TeV
D6T
1.0E-04
pyZ1+ SIM
Tune Z1
1.0E-02
1.0E-03
900 GeV
CMS
1.0E-01
Probability
Probability
PT(chgjet#1) > 3 GeV/c
7 TeV
1.0E-03
900 GeV
1.0E-04
DW
1.0E-05
1.0E-05
Normalized to 1
Normalized to 1
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-06
1.0E-06
0
5
10
15
20
25
30
35
40
45
50
0
PTsum (GeV/c)
5
10
15
20
25
30
35
40
45
50
PTsum (GeV/c)
 CMS uncorrected data at 900 GeV and 7 TeV  CMS uncorrected data at 900 GeV and 7 TeV
Difficult
to produce
on the charged scalar PTsum distribution in
on the charged
scalar PTsum
distribution in
enough
events
with
the “transverse” region for charged particles
the “transverse” region for charged particles
large
“transverse”
(pT > 0.5 GeV/c, |h| < 2) as defined by the
(pT > 0.5 GeV/c,
|h| <
2) as defined by the
PTsum
leading charged particle jet with
leading charged particleatjetlow
with
hard
scale!
PT(chgjet#1) > 3 GeV/c compared with
PT(chgjet#1) > 3 GeV/c compared with
PYTHIA Tune DW, and Tune D6T at the
PYTHIA Tune Z1, at the detector level (i.e.
detector level (i.e. Theory + SIM).
Theory + SIM).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 50
“Transverse” Multiplicity Distribution
"Transverse" Charged Particle Multiplicity
"Transverse" Charged Particle Multiplicity
Same
center-of-mass
1.0E+00
energy at two different 7 TeV
1.0E-01
hard scales!
CMS
1.0E+00
7 TeV
CMS Preliminary
data uncorrected
Theory + SIM
1.0E-01
CMS
1.0E-02
1.0E-02
data uncorrected
pyZ1 + SIM
Tune Z1
PT(chgjet#1) > 20 GeV/c
Probability
Probability
PT(chgjet#1) > 20 GeV/c
D6T
1.0E-03
CMS Preliminary
1.0E-04
PT(chgjet#1) > 3 GeV/c
1.0E-03
1.0E-04
PT(chgjet#1) > 3 GeV/c
1.0E-05
1.0E-05
DW
Normalized to 1
Normalized to 1
1.0E-06
1.0E-06
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-07
1.0E-07
0
5
10
15
20
25
30
35
40
0
Number of Charged Particles
5
10
15
20
25
30
35
40
Number of Charged Particles
Difficult
 CMS uncorrected
datatoatproduce
7 TeV on the
 CMS uncorrected data at 7 TeV on the
enough
events with
charged particle
multiplicity
distribution in
charged particle multiplicity distribution in
large
“transverse”
region
for charged particles
the “transverse” region for charged particles the “transverse”
multiplicity
low by the
(pT > 0.5 GeV/c,
|h| < 2) as at
defined
(pT > 0.5 GeV/c, |h| < 2) as defined by the
hard scale!
jet with PT(chgjet#1)
leading charged particle jet with PT(chgjet#1) leading charged particle
> 3 GeV/c and PT(chgjet#1) > 20 GeV/c
> 3 GeV/c and PT(chgjet#1) > 20 GeV/c
compared with PYTHIA Tune DW and Tune compared with PYTHIA Tune Z1 at the
D6T at the detector level (i.e. Theory + SIM). detector level (i.e. Theory + SIM).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 51
“Transverse” PTsum Distribution
Same center-of-mass
"Transverse" Charged PTsum Distribution
energy 1.0E+00
at two different
7 TeV
CMS Preliminary
hard scales!
data uncorrected
"Transverse" Charged PTsum Distribution
1.0E+00
7 TeV
CMS Preliminary
data uncorrected
Theory + SIM
1.0E-01
CMS
1.0E-02
CMS
1.0E-02
PT(chgjet#1) > 20 GeV/c
Probability
Probability
1.0E-01
1.0E-03
PT(chgjet#1) > 3 GeV/c
1.0E-04
pyZ1 + SIM
Tune Z1
PT(chgjet#1) > 20 GeV/c
1.0E-03
PT(chgjet#1) > 3 GeV/c
1.0E-04
D6T
Normalized to 1
1.0E-05
Normalized to 1
1.0E-05
DW
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-06
1.0E-06
0
5
10
15
20
25
30
35
40
45
50
0
PTsum (GeV/c)
5
10
15
20
25
30
35
40
45
50
PTsum (GeV/c)
 CMS uncorrected data at 7 TeV on the charged  CMS uncorrected data at 7 TeV on the charged
Difficultintothe
produce
PTsum distribution
“transverse” region for
PTsum distribution in the “transverse” region
enough
events
with |h| < 2) as
charged particles (pT > 0.5 GeV/c,
for charged particles (pT > 0.5 GeV/c, |h| < 2)
“transverse”
defined by thelarge
leading
charged particle jet with
as defined by the leading charged particle jet
PTsum
lowPT(chgjet#1) > 20
PT(chgjet#1) > 3 GeV/catand
with PT(chgjet#1) > 3 GeV/c and PT(chgjet#1)
GeV/c compared hard
with scale!
PYTHIA Tune Z1 at the
> 20 GeV/c compared with PYTHIA Tune DW
detector level (i.e. Theory + SIM).
and Tune D6T at the detector level (i.e. Theory
+ SIM).
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 52
CMS dN/dh
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
8
RDF Preliminary
RDF Preliminary
Charged Particle Density
Charged Particle Density
8
6
Tune Z1
4
CMS
2
CMS NSD 7 TeV
7 TeV
pyZ1 HC (6.51)
pyZ1 NSD (5.58)
0
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
6
4
CMS
2
CMS NSD 7 TeV
7 TeV
pyX2 NSD (5.91)
pyZ1 NSD (5.58)
CMS NSD all pT
0
-3.0
-2.5
-2.0
PseudoRapidity h
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
PseudoRapidity h
 Generator level dN/dh (all pT). Shows
the NSD = HC + DD and the HC = ND
contributions for Tune Z1. Also shows
the CMS NSD data.
 Generator level dN/dh (all pT). Shows
the NSD = HC + DD prediction for
Tune Z1 and Tune X2. Also shows the
CMS NSD data.
“Minimum Bias” Collisions
Okay not perfect, but remember
Proton
we do not know if the DD is correct!
Proton
UF-IFT Seminar
Gainesville, FL, November 19, 2010
3.0
Rick Field – Florida/CDF/CMS
Page 53
PYTHIA Tune Z1
Charged Particle Density: dN/dh
5
Charged Particle Density
RDF Preliminary
4
ALICE INEL data
pyZ1 generator level
At Least 1 Charged Particle |h| < 0.8
900 GeV
pT > 0.15 GeV/c
3
pT > 0.5 GeV/c
2
pT > 1.0 GeV/c
1
0
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
PseudoRapidity h
 ALICE inelastic data at 900 GeV on the dN/dh distribution for charged particles (pT >
PTmin) for events with at least one charged particle with pT > PTmin and |h| < 0.8 for
PTmin = 0.15 GeV/c, 0.5 GeV/c, and 1.0 GeV/c compared with PYTHIA Tune Z1 at the
generator level.
“Minumum Bias” Collisions
Okay
not perfect, but remember
Proton
Proton
we do not know if the SD & DD are correct!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 54
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
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Okay not perfect!
But not that bad!
Rick Field – Florida/CDF/CMS
Proton
Page 55
MB & UE
"Transverse" Charged Particle Multiplicity
Charged Multiplicity Distribution
1.0E+00
1.0E-01
“Min-Bias”
RDF Preliminary
PT(chgjet#1) > 3 GeV/c
data CMS NSD
pyZ1 generator level
CMS
1.0E-02
Probability
Probability
data uncorrected
pyZ1 + SIM
1.0E-01
CMS
1.0E-02
CMS Preliminary
7 TeV
Tune Z1
1.0E-03
7 TeV
900 GeV
1.0E-04
900 GeV
1.0E-03
“Underlying Event”
1.0E-05
Normalized to 1
Charged Particles
(all PT, |h|<2.0)
1.0E-04
0
20
1.0E-06
Difficult to produce
40
60
80
enough
events
with
Number of Charged Particles
large multiplicity!
1.0E-07
0
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.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Tune Z1
5
10
15
20
25
30
35
40
Number of Charged Particles
 CMS uncorrected
Difficult
datatoatproduce
900 GeV and 7
TeV on the charged
enoughparticle
events with
multiplicity
distribution inlarge
the “transverse”
“transverse” region
for charged particles
multiplicity
(pT >at0.5
low
GeV/c, |h|
< 2) as defined byhard
the leading
scale! charged
particle jet with PT(chgjet#1) > 3 GeV/c
compared with PYTHIA Tune Z1 at the
detector level (i.e. Theory + SIM).
Rick Field – Florida/CDF/CMS
Page 56
MB & UE
ChargedParticle
ParticleMultiplicity
Multiplicity
Charged
1.0E+00
1.0E+00
CMS
TeV
77 TeV
CMS Preliminary
Preliminary
CMS
Tune Z1
Z1
Tune
Min-Bias
NSD All pT
1.0E-01
1.0E-01
Probability
Probability
Min-Bias
NSD All pT
1.0E-02
1.0E-02
Underlying Event
"Transverse" Region
pT > 0.5 GeV/c
PT(chgjet#1) > 20 GeV/c
1.0E-03
1.0E-03
1.0E-04
1.0E-04
Normalizedto
to11
Normalized
Underlying Event
"Transverse" Region
pT > 0.5 GeV/c
PT(chgjet#1) > 20 GeV/c
Tune Z1
Charged Particles (|h|<2.0)
Charged Particles (|h|<2.0)
1.0E-05
1.0E-05
00
5
2010
1540
20
60
25
30 80 35
100
40
Number of
of Charged
Charged Particles
Particles
Number
 CMS uncorrected data at 7 TeV on the charged particle multiplicity distribution in the
“transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 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, |h| < 2) compared with Tune Z1 at the generator.
Amazing what we are asking the Monte-Carlo models to fit!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 57
Two Particle Angular Correlations
 Signal, S, is two particles in the
same event.
 Background, B, is two particles in
two different events.
“Minimum Bias” Collisions
Proton
Proton
 Correlation, R, is ~(S-B)/B.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 58
Two Particle Angular Correlations
CMS “min-bias” 7 TeV
x-axis
Bose-Einstein
Two Particles in Two Jets
y-axis
Jet#2
Jet#1
x-axis
Two Particles in Same Jet
y-axis
Jet#2
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Jet#1
Page 59
High Multiplicity at 7 TeV
Select Events with High Multiplicity
“Minimum Bias” Collisions
Proton
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Proton
Rick Field – Florida/CDF/CMS
Page 60
Two Particle Angular Correlations
High Multiplicity “Min-Bias”
Average “Min-Bias”
x-axis
Two Particles in Same Jet
y-axis
Jet#2
Jet#1
Lots of jets at high multiplicity!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 61
Two Particle Angular Correlations
High Multiplicity “Min-Bias”
Average “Min-Bias”
x-axis
Two Particles in Two Jets
y-axis
Jet#2
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Jet#1
Rick Field – Florida/CDF/CMS
Page 62
Long-Range Same-Side
Correlations
High Multiplicity “Min-Bias”
Not there in PYTHIA8!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
High Multiplicity “Min-Bias”
Also not there in PYTHIA 6 and HERWIG++!
Rick Field – Florida/CDF/CMS
Page 63
Correlation in Heavy Ion
Collisions
Long range correlations expected in “collective flow” in heavy ion collisions.
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 64
Correlation in Heavy Ion
Collisions
Long-range “Ridge”-like structure in Dh at Df ≈ 0!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 65
Proton-Proton vs Au-Au
Proton-Proton Collisions 7 TeV
Gold-Gold Collisions 200 GeV
QGP
I am not ready to jump on the
quark-gluon plasma bandwagon
quite yet!
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 66
Jet-Jet Correlations
 Are the “leading-log” or “modified leading-log” QCD Monte-Carlo Models missing
x-axis
an important QCD correlation?
 The leading jet and the incident protons
form a plane (yz-plane in the figure). This
is the plane of the hard scattering.
Proton
Proton
z-axis
Initial or FinalState Radiation
Leading Jet
y-axis
 Initial & final-state radiation prefers to lie in this plane. This is a higher order
effect that you can see in the 2→3 or 2→4 matrix elements, but it is not there if
you do 2→2 matrix elements and then add radiation using a naïve leading log
approximation (i.e. independent emission).
 I do not know to what extent this higher order jet-jet correlation is incorporated in
the QCD Monte-Carlo models.
 I would think that this jet-jet correlation would produce a long range (in Dh)
correlation with Df ≈ 0 from two particles with one in the leading jet and one in the
radiated jet. Why don’t we see this in the Monte-Carlo models?
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 67
Jet-Jet Correlations
x-axis
Proton
Proton
z-axis
Initial or FinalState Radiation
Leading Jet
y-axis
 Initial & Final-State Radiation: There
should be more particles “in-the-plane” of
the hard scattering (yz-plane in the figure)
than “out-of –the-plane”.
??
 I do not understand why this does not
result in a long-range same-side
correlation?
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 68
Min-Bias Summary
We are a long way from having a Monte-Carlo model that will fit all the
features of the LHC min-bias data! There are more soft particles that
expected!
We need a better understanding and modeling of diffraction!
It is difficult for the Monte-Carlo models to produce a soft event (i.e. no
large hard scale) with a large multiplicity. There seems to be more “minbias” high multiplicity soft events at 7 TeV than predicted by the models!
The models do not produce enough strange particles! I have no idea what is
going on here! The Monte-Carlo models are constrained by LEP data.
Color
Diffraction
Connections
UF-IFT Seminar
Gainesville, FL, November 19, 2010
Rick Field – Florida/CDF/CMS
Page 69
The LHC in 2011
 Beam back around 21st February.
 Beam back around on February 21st!
 2 weeks re-commissioning with beam (at
least).
technical stop every 6 weeks.
Thisis4 day
fun!
 4 weeks ion run.
 End of run – December 12th.
 Approximately 200 days proton physics!
 Maybe 8 TeV (4 TeV/beam).
Peak luminosity
UF-IFT Seminar
Gainesville, FL, November 19, 2010
6.4 x 1032
Integrated per day
11 pb-1
200 days
2.2 fb-1
Stored energy
72 MJ
Rick Field – Florida/CDF/CMS
Page 70