YETI’11: The Standard Model
at the Energy Frontier
Min-Bias and the Underlying Event at the LHC
Rick Field
University of Florida
2nd Lecture
 How well did we do at predicting the
behavior of the “underlying event” at
the LHC (900 GeV and 7 TeV)?
CMS
 How well did we do at predicting the
behavior of “min-bias” collisions at
the LHC (900 GeV and 7 TeV)?
 PYTHIA 6.4 Tune Z1: New CMS 6.4 tune
ATLAS
(pT-ordered parton showers and new MPI).
 New Physics in Min-Bias??
Observation of long-range same-side
correlations at 7 TeV.
 Strange particle production:
A problem for the models?
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
UE&MB@CMS
Rick Field – Florida/CDF/CMS
Page 1
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.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 2
“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).
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
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 3
“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
Monte-Carlo!
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
Real Data!
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).
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
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 4
“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
Monte-Carlo!
CMS Preliminary
data uncorrected
pyDW + SIM
0.6
ChgJet#1
PTmax
0.4
0.2
900 GeV
Real Data!
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
data (from PYTHIA Tune DW) are
are uncorrected and compared with
generated at the particle level (i.e. generator
PYTHIA Tune DW after detector simulation
level) assuming 0.5 M min-bias events at 900
(216,215 events in the plot).
GeV (361,595 events in the plot).
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 5
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.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 6
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)
I read the points off
with a ruler!
 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.
ATLAS Note: ATLAS-CONF-2010-029
May 29, 2010
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 7
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
 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.
16
18
20
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.
PT(chgjet#1) Direction
PTmax Direction
Df
Df
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
14
PTmax (GeV/c)
PT(chgjet#1) GeV/c
“Transverse”
12
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 8
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
PT(chgjet#1) Direction
simulation.
Df
8
10
12
14
16
18
 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”
“Toward”
“Transverse”
“Transverse”
“Away”
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
6
PTmax (GeV/c)
PT(chgjet#1) (GeV/c)
“Transverse”
4
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 9
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).
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 10
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
leading charged particle jet (chgjet#1) for
particle jet (chgjet#1) for charged particles
charged particles with pT > 0.5 GeV/c and
with pT > 0.5 GeV/c and |h| < 2. The data are
|h| < 2. The data are uncorrected and
uncorrected and compared with PYTHIA
compared with PYTHIA Tune DW after
Tune DW after detector simulation.
PT(chgjet#1) Direction
PT(chgjet#1) Direction
detector simulation.
Df
Df
“Toward”
“Transverse”
“Toward”
“Transverse”
“Transverse”
“Away”
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 11
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
PT(chgjet#1) Direction
detector simulation.
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
PTmax Direction
Tune DW at the generator
level.
Df
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
3
PTmax (GeV/c)
PT(chgjet#1) (GeV/c)
“Transverse”
2
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 12
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
PT(chgjet#1) Direction
detector simulation.
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. PTmax Direction
“Toward”
Df
“Toward”
“Transverse”
“Transverse”
“Away”
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
3
PTmax (GeV/c)
PT(chgjet#1) (GeV/c)
“Transverse”
2
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 13
“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.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 14
“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.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 15
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)
30
35
40
45
50
"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!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
25
PT(chgjet#1) GeV/c
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
Rick Field – Florida/CDF/CMS
4
6
8
10
12
14
16
18
PT(chgjet#1) (GeV/c)
Page 16
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)
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 17
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 thatWethe
Tunes did as well
do not know if the models correctly
as they did at predicting
thethebehavior
of pT values!
describe
UE at lower
the “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!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Final-State
Radiation
PARP(82)
PARP(90)
Color
Diffraction
Connections
Page 18
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 -2.5
-2.0 -1.5 data
-1.0 -0.5
0.0 PYTHIA
0.5
1.0
1.5 Tune
2.0
2.5
3.0 and Tune S320
 Compares the 900 GeV
ALICE
with
DW
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.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 19
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!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Soft particles!
Rick Field – Florida/CDF/CMS
Page 20
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.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 21
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
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 22
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
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Off by 50%!
Rick Field – Florida/CDF/CMS
Proton
Page 23
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!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
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 24
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
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 25
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
 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 uncorrected and compared
with PYTHIA Tune DW and D6T after
detector simulation (SIM).
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
15
20
25
30
35
40
45
50
PT(chgjet#1) GeV/c
PT(chgjet#1) GeV/c
Color reconnection suppression.
Color reconnection strength.
10
 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 uncorrected and compared
with PYTHIA Tune Z1 after detector
simulation (SIM).
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 26
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
 CMS preliminary data at 900 GeV and 7
TeV on the “transverse” charged PTsum
TeV on the “transverse” charged PTsum
density, dPT/dhdf, as defined by the leading
density, dPT/dhdf, as defined by the leading
charged particle jet (chgjet#1) for charged
charged particle jet (chgjet#1) for charged
particles with pT > 0.5 GeV/c and |h| < 2.0.
particles with pT > 0.5 GeV/c and |h| < 2.0.
The data are uncorrected and compared
The data are uncorrected and compared
with PYTHIA Tune DW and D6T after
with PYTHIA Tune Z1 after detector
detector simulation (SIM).
simulation (SIM).
Color reconnection suppression.
Color reconnection strength.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
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 27
PYTHIA Tune Z1
"Transverse" Charged PTsum Density: dPT/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.5
RDF Preliminary
RDF Preliminary
7 TeV
ALICE corrected data
Tune Z1 generator level
PTsum Density (GeV/c)
"Transverse" Charged Density
1.2
0.8
900 GeV
0.4
ALICE
Tune Z1
7 TeV
ALICE corrected data
Tune Z1 generator level
1.0
900 GeV
0.5
ALICE
Tune Z1
Charged Particles (|h|<0.8, PT>0.5 GeV/c)
Charged Particles (|h|<0.8, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
0
5
 ALICE 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.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
15
20
25
PTmax (GeV/c)
PTmax (GeV/c)
I read the points off
with a ruler!
10
 ALICE 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| < 0.8.
The data are corrected and compared with
PYTHIA Tune Z1 at the generrator level.
ALICE UE Data: Talk by S. Vallero
MPI@LHC 2010 Glasgow, Scotland
November 30, 2010
Rick Field – Florida/CDF/CMS
Page 28
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
4
6
PTmax (GeV/c)
10
12
14
16
18
 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.
ATLAS Note: ATLAS-CONF-2010-029
May 29, 2010
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
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 Z1 at the generator level.
I read the points off
with a ruler!
8
Rick Field – Florida/CDF/CMS
Page 29
PYTHIA Tune Z1
"Transverse" Charged Particle Density: dN/dhdf
2.5
1.5
1.0
0.5
3.0
2.0
0.0
2
4
6
ATLAS
Factor of 2 increase!
Charged Particles (|h|<2.5)
7 TeV
RDF Preliminary
2.0
PT > 0.1 GeV/c
generator level
Tune Z1 (solid)
Tune DW (dashed)
1.0
ATLAS
0.5
PT > 0.5 GeV/c
Tune Z1
Charged Particles (|h|<2.5)
0.0
1.0
8
RDF Preliminary
ATLAS corrected data
Tune Z1 generator level
Charge Particle1.5
Density
PT > 0.5 GeV/c
Tune Z1
0
"Transverse" PTsum Density
7 TeV
ATLAS corrected data
Tune Z1 generator level
2.0
PT > 0.1 GeV/c
4.0
RDF Preliminary
"Transverse" Ratio 0.1/0.5
"Transverse" Charged Density
"Transverse" Charged PTsum Density: dPT/dhdf
"Transverse" Ratio: PT >2.50.1 and > 0.5 GeV/c
10
12
PTmax (GeV/c)
14
16
18
Charge PTsum Density
20
0
2
4
76 TeV 8
10
12
14
16
18
20
Charged Particles
(|h|<2.5)
PTmax
(GeV/c)
0.0
 ATLAS preliminary data
at 27 TeV4 on the
 10ATLAS
preliminary
data20at 7 TeV on the
0
6
8
12
14
16
18
“transverse” charged particle density,
“transverse” charged PTsum density,
PTmax (GeV/c)
dN/dhdf, as defined by the leading charged
dPT/dhdf, as defined by the leading charged
particle (PTmax) for charged particles with
particle (PTmax) for charged particles with
pT > 0.5 GeV/c and |h| < 2.5. The data are
pT > 0.5 GeV/c and |h| < 2.5. The data are
corrected and compared with PYTHIA Tune
corrected and compared with PYTHIA Tune
Z1 at the generator level. Also shows the
Z1 at the generator level. Also shows the
prediction of Tune Z1 for the “transverse”
prediction of Tune Z1 for the “transverse”
charged particle density with pT > 0.1 GeV/c
Rick Fieldcharged particle density with pT > 0.1 GeV/c
and |h| < 2.5.
and |h| < 2.5.
MPI@LHC 2010 Glasgow, Scotland
December 2, 2010
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 30
PYTHIA Tune Z1
"Transverse"Charged
ChargedParticle
Particle Density:
Density: dN/dhdf
dN/dhdf
"Transverse"
"Transverse"
1.5
1.5
1.0
1.0
Tune Z1
7 TeV
0.0
0.0
00
22
44
2.5
PT > 0.1 GeV/c
7 TeV
ATLAS corrected data
ATLAS corrected data
Tune Z1 generator level
Tune Z1 generator level
0.5
0.5
"Transverse" Charged PTsum Density:
Density: dPT/dhdf
dPT/dhdf
Ratio: PT > 0.1 "Transverse"
and
> 0.5 GeV/c
66
PTsum Density
(GeV/c)
"Transverse"
PTsum
Density
2.0
2.0
4.0
RDFPreliminary
Preliminary
RDF
"Transverse" Ratio 0.1/0.5
"Transverse"
Density
"Transverse" Charged
Charged Density
2.5
2.5
RDF Preliminary
RDF
Preliminary
ATLAS
ATLAScorrected
correcteddata
data
RDF
Tune
TuneZ1
Z1generator
generatorlevel
level
2.0
ATLAS corrected data
Tune Z1 generator level
Tune Z1
Charge Particle Density
3.0
PTPT
> 0.1
GeV/c
> 0.5
GeV/c
2.0
PT > 0.5 GeV/c
ATLAS
Charged
Particles
(|h|<2.5)
Charged
Particles
(|h|<2.5)
1.5
PT > 0.1 GeV/c
PT > 0.1 GeV/c
1.0
ATLAS
PT > 0.5 GeV/c
PT > 0.5 GeV/c
0.5
Charged Particles (|h|<2.5)
Charged Particles (|h|<2.5)
7 TeV
0.0
1.0
88
7 TeV
Preliminary
10
10
12
12
PTmax (GeV/c)
(GeV/c)
PTmax
14
14
16
16
18
18
20
20
Charge PTsum Density
0
2
4
76 TeV 8
10
12
14
16
18
20
(GeV/c)
(GeV/c)
Charged ParticlesPTmax
(|h|<2.5)
 ATLAS preliminary0.0data at 7 TeV on the
10 ATLAS
preliminary
data20at 7 TeV on the
0
2
4
6
8
12
14
16
18
“transverse” charged particle density,
“transverse” charged PTsum density,
PTmax (GeV/c)
dN/dhdf, as defined by the leading charged
dPT/dhdf, as defined by the leading charged
particle (PTmax) for charged particles with
particle (PTmax) for charged particles with
pT > 0.5 GeV/c and pT > 0.1 GeV/c (|h| < 2.5).
pT > 0.5 GeV/c and pT > 0.1 GeV/c (|h| < 2.5).
The data are corrected and compared with
The data are corrected and compared with
PYTHIA Tune Z1 at the generator level.
PYTHIA Tune Z1 at the generator level.
I read the points off
with a ruler!
ATLAS publication – arXiv:1012.0791
December 3, 2010
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 31
“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
5
10
15
20
25
30
35
40
Number of Charged Particles
Difficultdata
to produce
CMS uncorrected
at 900 GeV and
enough
events
with
7 TeV on the charged particle
“transverse”
multiplicitylarge
distribution
in the
multiplicity
at
low
“transverse” region for charged
hard
scale!|h| < 2) as
particles (pT > 0.5
GeV/c,
defined by the leading charged particle
jet with PT(chgjet#1) > 3 GeV/c
compared with PYTHIA Tune Z1 at the
detector level (i.e. Theory + SIM).
Rick Field – Florida/CDF/CMS
Page 32
 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 with PT(chgjet#1) > 3 GeV/c
compared with PYTHIA Tune DW and Tune
D6T at the detector level (i.e. Theory + SIM).
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
0
“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
 CMS uncorrected data at 900 GeV and 7
Difficultscalar
to produce
TeV on the charged scalar PTsum
TeV on the charged
PTsum
enough
events
with region for
distribution in the “transverse” region for
distribution in the “transverse”
large (p
“transverse”
charged particles (pT > 0.5 GeV/c, |h| < 2) as
charged particles
T > 0.5 GeV/c, |h| < 2) as
PTsum
low particle jet
defined by the leading charged particle jet
defined by the leading at
charged
hard
with PT(chgjet#1) > 3 GeV/c compared with
with PT(chgjet#1)
> 3 scale!
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).
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 33
“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
Number of Charged Particles
35
40
0
5
10
15
20
25
30
35
40
Number of Charged Particles
Difficult
to at
produce
 CMS uncorrected
data
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
largeregion
“transverse”
for charged particles
the “transverse” region for charged particles the “transverse”
multiplicity
low by the
(pT > 0.5 GeV/c,
|h| < 2) asatdefined
(pT > 0.5 GeV/c, |h| < 2) as defined by the
hard scale!
leading charged particle
jet with
leading charged particle jet with
PT(chgjet#1) > 3 GeV/c and PT(chgjet#1) >
PT(chgjet#1) > 3 GeV/c and PT(chgjet#1) >
20 GeV/c compared with PYTHIA Tune DW 20 GeV/c compared with PYTHIA Tune Z1
at the detector level (i.e. Theory + SIM).
and Tune D6T at the detector level (i.e.
Theory
+ SIM).
YETI'11
Durham
IPPP - Part 2
Rick Field – Florida/CDF/CMS
Page 34
January 10-12, 2011
“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
Difficult in
to the
produce
PTsum distribution
“transverse” region
charged PTsum distribution in the
enough
events
with
for charged particles (pT > 0.5 GeV/c, |h| < 2) as
“transverse” region for charged particles (pT
large
“transverse”
defined by the
leading
charged particle jet with
> 0.5 GeV/c, |h| < 2) as defined by the leading
PTsum
at
low PT(chgjet#1) > 20
PT(chgjet#1) > 3 GeV/c and
charged particle jet with PT(chgjet#1) > 3
hard
GeV/c compared
withscale!
PYTHIA Tune Z1 at the
GeV/c and PT(chgjet#1) > 20 GeV/c
detector level (i.e. Theory + SIM).
compared with PYTHIA Tune DW and Tune
D6T at the detector level (i.e. Theory + SIM).
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 35
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
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
3.0
Rick Field – Florida/CDF/CMS
Page 36
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!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 37
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
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Okay not perfect!
But not that bad!
Rick Field – Florida/CDF/CMS
Proton
Page 38
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
100
0
5
10
15
20
25
30
35
40
Number of Charged Particles
 CMS uncorrected
Difficult
data
to produce
at 900 GeV and
7 TeV on theenough
charged
events
particle
with
multiplicity distribution
large “transverse”
in the
“transverse”multiplicity
region for charged
at low
particles (pT > 0.5
hard
GeV/c,
scale!
|h| < 2) as
defined by the leading charged particle
jet with PT(chgjet#1) > 3 GeV/c
compared with PYTHIA Tune Z1 at the
detector level (i.e. Theory + SIM).
Rick Field – Florida/CDF/CMS
Page 39
 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.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Tune Z1
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!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 40
New Physics in “Min-Bias”?
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
The Inelastic Cross Section
Proton
Proton
+
Proton
+
Proton
Proton
Proton
+
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
 CMS Two-Particle Correlations at 7 TeV.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 41
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.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 42
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
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Jet#1
Page 43
High Multiplicity at 7 TeV
Select Events with High Multiplicity
“Minimum Bias” Collisions
Proton
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Proton
Rick Field – Florida/CDF/CMS
Page 44
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!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 45
Two Particle Angular Correlations
High Multiplicity “Min-Bias”
Average “Min-Bias”
x-axis
Two Particles in Two Jets
y-axis
Jet#2
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Jet#1
Rick Field – Florida/CDF/CMS
Page 46
Long-Range Same-Side
Correlations
High Multiplicity “Min-Bias”
Not there in PYTHIA8!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
High Multiplicity “Min-Bias”
Also not there in PYTHIA 6 and HERWIG++!
Rick Field – Florida/CDF/CMS
Page 47
Correlation in Heavy Ion
Collisions
 Long range correlations expected in “collective flow” in heavy ion
collisions.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 48
Correlation in Heavy Ion
Collisions
 Long-range “Ridge”-like structure in Dh at Df ≈ 0!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 49
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!
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 50
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?
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 51
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?
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 52
Strange Particle Production
Factor of 2!
ALICE preliminary
stat. error only
Phojet
Pythia ATLAS-CSC
Pythia D6T
Pythia Perugia-0
 A lot more strange mesons at large pT than predicted by the Monte-Carlo
Models!
 K/ ratio fairly independent of the center-of-mass energy.
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 53
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
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
Rick Field – Florida/CDF/CMS
Page 54
The LHC in 2011

Beam back around 21st February.
 Beam back around on February 21st!
 2 weeks re-commissioning with beam (at
least).
day technical stop every 6 weeks.
Thisis4fun!
 4 weeks ion run.
 End of run – December 12th.
 Approximately 200 days proton physics!
 Maybe 8 TeV (4 TeV/beam).
Peak luminosity
YETI'11 Durham IPPP - Part 2
January 10-12, 2011
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 55