QCD at the LHC
LHC UE & MB MC Tunes
Rick Field
University of Florida
Outline of Talk
 How well did we do at predicting the LHC UE
data at 900 GeV and 7 TeV? A careful look.
 How well did we do at predicting the LHC MB
data at 900 GeV and 7 TeV? A careful look.
 PYTHIA 6.4 Tune Z1: New CMS 6.4 tune (pTordered parton showers and new MPI).
 PYTHIA 8 Tune: New tune from Hendrik Hoeth.
 Long-Range Same-Side Correlations: Collective
Outgoing 28,
Parton2010
Trento, Italy, September
PT(hard)
Initial-State Radiation
Proton
phenomena in pp collisions at 7 TeV?? New type of
“underlying event”!
 Strange particle production: A problem for the models?
ECT* - QCD at the LHC
Trento September 28, 2010
Proton
Underlying Event
Rick Field – Florida/CDF/CMS
Underlying Event
UE&MB@CMS
Outgoing Parton
Final-State
Radiation
Page 1
PYTHIA Tune DW
"Transverse" Charged Particle Density: dN/dhdf
1.2
PT(chgjet#1) Direction
Charged Particle Density
CMS Preliminary
f
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.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 2
PYTHIA Tune DW
PTmax Direction
f
“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.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 3
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
f
f
“Toward”
“Transverse”
“Toward”
“Transverse”
“Transverse”
“Away”
ECT* - QCD at the LHC
Trento September 28, 2010
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 4
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.
f
10
12
14
16
18
“Toward”
“Transverse”
“Transverse”
“Away”
ECT* - QCD at the LHC
Trento September 28, 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 Directionf
“Toward”
“Transverse”
6
PTmax (GeV/c)
PT(chgjet#1) (GeV/c)
PT(chgjet#1) Direction
4
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 5
20
PYTHIA Tune DW
"Transverse" Charged Particle Density: dN/dhdf
1.2
PT(jet#1) Direction
“Toward”
“Transverse”
“Transverse”
“Away”
CDF Published
Charged Particle Density
f
1.96 TeV
data corrected
pyDW generator level
0.8
CDF
0.4
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
50
100
150
200
250
300
350
PT(jet#1) GeV/c
 CDF published data at 1.96 TeV on the
“transverse” charged particle density,
dN/dhdf, as defined by the leading
calorimeter jet (jet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 1.0. The data
are corrected and compared with PYTHIA
Tune DW at the generator level.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 6
400
PYTHIA Tune DW
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.2
1.2
CDF Published
7 TeV
data uncorrected
pyDW + SIM
Charged Particle Density
Charged Particle Density
CMS Preliminary
0.8
CMS
900 GeV
0.4
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.96 TeV
data corrected
pyDW generator level
0.8
CDF
0.4
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
30
35
40
45
50
0
50
100
150
200
 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.
350
 CDF published data at 1.96 TeV on the
“transverse” charged particle density,
dN/dhdf, as defined by the leading
calorimeter jet (jet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 1.0. The data
are corrected and compared with PYTHIA
Tune DW at the generator level.
PT(chgjet#1) Direction
PT(jet#1) Direction
f
f
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
ECT* - QCD at the LHC
Trento September 28, 2010
300
PT(jet#1) GeV/c
PT(chgjet#1) GeV/c
“Transverse”
250
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 7
400
PYTHIA Tune DW
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.2
1.2
RDF Preliminary
7 TeV
data uncorrected
pyDW + SIM
Charged Particle Density
Charged Particle Density
CMS Preliminary
0.8
CMS
900 GeV
0.4
CMS 7 TeV
Tune DW
CDF 1.96 TeV
0.8
CMS 900 GeV
0.4
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
30
35
40
45
50
0
10
20
30
40
50
60
70
80
90
100
PT(chgjet#1 or jet#1) GeV/c
PT(chgjet#1) GeV/c
 CMS preliminary data at 900 GeV and 7 TeV  CDF published data at 1.96 TeV on the
on the “transverse” charged particle density,
“transverse” charged particle density,
dN/dhdf, as defined by the leading charged
dN/dhdf, as defined by the leading
particle jet (chgjet#1) for charged particles
calorimeter jet (jet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 2. The data are
with pT > 0.5 GeV/c and |h| < 1.0. The data
uncorrected and compared with PYTHIA
are corrected and compared with PYTHIA
Tune DW after detector simulation.
Tune DW at the generator level.
PT(chgjet#1) Direction
PT(jet#1) Direction
f
f
“Toward”
“Transverse”
“Toward”
“Transverse”
“Transverse”
“Away”
ECT* - QCD at the LHC
Trento September 28, 2010
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 8
“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
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
20
PTmax (GeV/c)
PTmax Direction
f
LHC
900 GeV
“Toward”
“Transverse”
PTmax Direction
900 GeV → 7 TeV
(UE increase ~ factor of 2)
“Transverse”
“Away”
~0.4 → ~0.8
f
“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).
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 9
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
f
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 Directionf
“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
ECT* - QCD at the LHC
Trento September 28, 2010
3
PTmax (GeV/c)
PT(chgjet#1) (GeV/c)
“Transverse”
2
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 10
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
f
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
f
“Toward”
“Transverse”
“Transverse”
“Away”
ECT* - QCD at the LHC
Trento September 28, 2010
3
PTmax (GeV/c)
PT(chgjet#1) (GeV/c)
“Transverse”
2
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 11
“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
7 TeV
900 GeV
f
1.0E-04
“Toward”
1.0E-05
Normalized to 1
“Transverse”
“Transverse”
1.0E-06
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
“Away”
1.0E-07
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.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 12
“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
f
1.0E-04
PT(chgjet#1) > 3 GeV/c
1.0E-05
CMS
Normalized to 1
1.0E-06
“Toward”
“Transverse”
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
“Transverse”
“Away”
1.0E-07
0
5
10
15
20
25
30
35
40
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.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 13
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)
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 14
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
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!
Remember this is “soft” QCD!
Outgoing Parton
“Min-Bias” is a whole different story!
Much more complicated due to
diffraction!
ECT* - QCD at the LHC
Trento September 28, 2010
Underlying Event
Rick Field – Florida/CDF/CMS
Final-State
Radiation
PARP(82)
PARP(90)
Color
Diffraction
Connections
Page 15
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.
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
diffraction!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Final-State
Radiation
PARP(82)
PARP(90)
Color
Diffraction
Connections
Page 16
Rick Field University of Chicago
July 11, 2006
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“Toward”
“TransMAX”
“TransMIN”
“Away”
“Toward”
“TransMAX”
“TransMIN”
“Away”
"Transverse" ETsum Density (GeV)
f
f
"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)
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 17
Rick Field University of Chicago
July 11, 2006
“Leading Jet”
“Back-to-Back”
Jet #1 Direction
Jet #1 Direction
“Toward”
“TransMAX”
“TransMIN”
“Away”
f
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)
f
"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)
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 18
Rick Field University of Chicago
July 11, 2006
“Leading Jet”
Jet #1 Direction
f
"TransDIF" ETsum Density: dET/dhdf
“Toward”
Jet #1 Direction
f
“TransMIN”
“Away”
“Toward”
“TransMAX”
“TransMIN”
“Away”
Jet #2 Direction
“Back-to-Back”
"Transverse" ETsum Density (GeV)
“TransMAX”
5.0
CDF Run 2 Preliminary
data corrected to particle level
4.0
"Leading Jet"
1.96 TeV
3.0
PY Tune A
2.0
HW
"Back-to-Back"
1.0
MidPoint R = 0.7 |h(jet#1) < 2
Particles (|h|<1.0, all PT)
0.0
“transDIF” is more sensitive to
the “hard scattering” component
of the “underlying event”!
0
50
100
150
200
250
300
350
400
450
PT(jet#1) (GeV/c)
 Use the leading jet to define the MAX and MIN “transverse” regions on an event-byevent basis with MAX (MIN) having the largest (smallest) charged PTsum density.
 Shows the “transDIF” = MAX-MIN ETsum density, dETsum/dhdf, for all particles (|h| <
1) versus PT(jet#1) for “Leading Jet” and “Back-to-Back” events.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 19
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)
ECT* - QCD at the LHC
Trento September 28, 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 20
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
UA5 INEL
INEL = HC+DD+SD
900 GeV
1
pyDW INEL (2.67)
4
3
2
1
pyS320 INEL (2.70)
Charged Particles (all pT)
UA5
ALICE
NSD = HC+DD
900 GeV
pyDW_10mm (3.04)
pyS320_10mm (3.09)
0
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
-3.0
-2.5
-2.0
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
PseudoRapidity h
PseudoRapidity h
“Minumum Bias” Collisions
“Minumum Bias” Collisions
Proton
-1.5
Proton
Proton
Proton
 Compares the 900 GeV ALICE data with PYTHIA Tune DW and Tune S320
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.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 21
3.0
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
“Minumum Bias” Collisions
“Minumum 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 data
-2.5 -2.0
-1.5 PYTHIA
-1.0 -0.5 0.0 Tune
0.5
1.0 DW
1.5 and
2.0
2.5
3.0
 Compares the 900 GeV
with
Tune
S320 Perugia 0.
PseudoRapidity
h
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.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 22
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!
ECT* - QCD at the LHC
Trento September 28, 2010
Soft particles!
Rick Field – Florida/CDF/CMS
Page 23
PYTHIA Tune DW
If one increases the
hard scale the
agreement improves!
Charged Particle Density: dN/dh
5
Charged Particle Density
RDF Preliminary
4
ALICE INEL data
pyDW generator level
At Least 1 Charged Particle |h| < 0.8
900 GeV
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.
The same thing occurs at 7 TeV!
ALICE, ATLAS, and CMS data coming soon.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 24
PYTHIA Tune DW
Diffraction
contributes less at
harder scales!
Charged Particle Density: dN/dh
5
Charged Particle Density
RDF Preliminary
4
ALICE INEL data
pyDW generator level
At Least 1 Charged Particle |h| < 0.8
900 GeV
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).
Cannot trust PYTHIA 6.2 modeling of diffraction!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 25
CMS dN/dh
Charged Particle Density: dN/dh
8
CMS
Charged Particle Density
7 TeV
6
4
RDF Preliminary
2
Tune DW
CMS NSD data
pyDW generator level
All pT
dashed = ND solid = NSD
0
-3.0
-2.5
-2.0
-1.5
-1.0
Soft particles!
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
PseudoRapidity h
 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.
Off by 50%!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 26
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
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
to fit the
data!
PseudoRapidity h
2
Soft particles!
2.5
3.0
 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.
Off by 50%!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 27
CMS dN/dh
Charged Particle Density: dN/dh
8
Charged Particle Density
7 TeV
CMS
6
4
RDF Preliminary
Okay if the Monte-Carlo doesTune
not DW
fit
Soft particles!
2
the data what do we do?
dashed = ND solid = NSD
All pT
We
tune
the
Monte-Carlo
0
-3.0 -2.5 -2.0 -1.5
-1.0 the
-0.5 data!
0.0
0.5
1.0
1.5
2.0
2.5
3.0
to fit
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.
CMS NSD data
pyDW generator level
Off by 50%!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 28
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!
ECT* - QCD at the LHC
Trento September 28, 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 29
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
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 30
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.
ECT* - QCD at the LHC
Trento September 28, 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 31
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.
ECT* - QCD at the LHC
Trento September 28, 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 32
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)
ECT* - QCD at the LHC
Trento September 28, 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 33
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).
ECT* - QCD at the LHC
Trento September 28, 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 34
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).
ECT* - QCD at the LHC
Trento September 28, 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 35
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.
ECT* - QCD at the LHC
Trento September 28, 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 36
PYTHIA Tune Z1
"Transverse" Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.2
Charged Particle Density
"Transverse" Charged Density
1.2
CMS Preliminary
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
CDF Run 2
1.96 TeV
data corrected
pyZ1 generator level
0.8
Tune Z1
0.4
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
CDF
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
5
10
15
20
25
30
35
40
45
50
0
50
PT(chgjet#1) GeV/c
100
150
200
250
300
350
400
PT(jet#1) (GeV/c)
 CMS preliminary data at 900 GeV and 7 TeV  CDF published data at 1.96 TeV on the
on the “transverse” charged particle density,
“transverse” charged particle density,
dN/dhdf, as defined by the leading charged
dN/dhdf, as defined by the leading
particle jet (chgjet#1) for charged particles
calorimeter jet (jet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 2. The data are
with pT > 0.5 GeV/c and |h| < 1.0. The data
uncorrected and compared with PYTHIA
are corrected and compared with PYTHIA
Tune Z1 after detector simulation.
Tune Z1 at the generator level.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 37
PYTHIA Tune Z1
Oops Tune Z1 is
"Transverse"
slightly high
at CDF!Charged Particle Density: dN/dhdf
"Transverse" Charged Particle Density: dN/dhdf
1.2
Charged Particle Density
"Transverse" Charged Density
1.2
CMS Preliminary
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
CDF Run 2
1.96 TeV
data corrected
pyZ1 generator level
0.8
Tune Z1
0.4
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
CDF
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
0.0
0
5
10
15
20
25
30
35
40
45
50
0
50
PT(chgjet#1) GeV/c
100
150
200
250
300
350
400
PT(jet#1) (GeV/c)
 CMS preliminary data at 900 GeV and 7 TeV  CDF published data at 1.96 TeV on the
on the “transverse” charged particle density,
“transverse” charged particle density,
dN/dhdf, as defined by the leading charged
dN/dhdf, as defined by the leading
particle jet (chgjet#1) for charged particles
calorimeter jet (jet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 2. The data are
with pT > 0.5 GeV/c and |h| < 1.0. The data
uncorrected and compared with PYTHIA
are corrected and compared with PYTHIA
Tune Z1 after detector simulation.
Tune Z1 at the generator level.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 38
PYTHIA Tune Z1
MPI Cut-Off PT0(Wcm)
3.5
RDF Very Preliminary
3.0
PT0 (GeV/c)
CDF 1.96 TeV
2.5
CMS 7 TeV
2.0
Tune Z1
pT0(W)=pT0(W/W0)e
1.5
CMS 900 GeV
1.0
0
2000
4000
6000
8000
10000
12000
Center-of-Mass Energy Wcm (GeV)
 MPI Cut-Off versus the Center-of Mass Energy Wcm: PYTHIA Tune Z1 was determined
by fitting pT0 independently at 900 GeV and 7 TeV and calculating e = PARP(90). The best
fit to pT0 at CDF is slightly higher than the Tune Z1 curve. This is very preliminary!
Perhaps with a global fit to all three energies (i.e. “Professor” tune) one can get a
simultaneous fit to all three??
pT0(W)=pT0(W/W0)e e = PARP(90) pT0 = PARP(82) W = Ecm
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 39
PYTHIA Tune Z1
MPI Cut-Off PT0(Wcm)
3.5
RDF Very Preliminary
3.0
PT0 (GeV/c)
CDF 1.96 TeV
2.5
CMS 7 TeV
2.0
Tune Z1
1.5
More UE activity for
W > 7 TeV!??
CMS 900 GeV
1.0
0
2000
4000
6000
8000
10000
12000
Center-of-Mass Energy Wcm (GeV)
 MPI Cut-Off versus the Center-of Mass Energy Wcm: PYTHIA Tune Z1 was determined
by fitting pT0 independently at 900 GeV and 7 TeV and calculating e = PARP(90). The best
fit to pT0 at CDF is slightly higher than the Tune Z1 curve. This is very preliminary!
Perhaps with a global fit to all three energies (i.e. “Professor” tune) one can get a
simultaneous fit to all three??
pT0(W)=pT0(W/W0)e e = PARP(90) pT0 = PARP(82) W = Ecm
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 40
PYTHIA 8 Tunes
Hendrik Hoeth ISMD2010
New PYTHIA 8
tune!
New PYTHIA 8.142 “professor” tune from Hendrik Hoeth.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 41
PYTHIA 8 Tunes
Hendrik Hoeth ISMD2010
New PYTHIA 8
tune!
New PYTHIA 8.142 “professor” tune from Hendrik Hoeth.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 42
PYTHIA 8 Tunes
Hendrik Hoeth ISMD2010
Low at 900 GeV!
New PYTHIA 8.142 “professor” tune from Hendrik Hoeth.
Fits nicely 1.96 TeV and 7 TeV, but is low at 900 GeV!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 43
“Transverse” Multiplicity Distribution
"Transverse" Charged Particle Multiplicity
"Transverse" Charged Particle Multiplicity
1.0E+00
1.0E+00
PT(chgjet#1) > 3 GeV/c
data uncorrected
Theory + SIM
1.0E-01
1.0E-01
Probability
1.0E-03
7 TeV
900 GeV
1.0E-04
D6T
1.0E-05
CMS Preliminary
data uncorrected
pyZ1 + SIM
CMS
1.0E-02
CMS
1.0E-02
Probability
PT(chgjet#1) > 3 GeV/c
CMS Preliminary
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
 CMS uncorrected data at 900 GeV and 7 TeV on  CMS uncorrected data at 900 GeV and 7
TeV on the charged particle multiplicity
the charged particle multiplicity distribution in
the “transverse” region for charged particles (pT > distribution in the “transverse” region
for charged particles (pT > 0.5 GeV/c, |h|
0.5 GeV/c, |h| < 2) as defined by the leading
< 2) as defined by the 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).
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 44
“Transverse” PTsum Distribution
"Transverse" Charged PTsum Distribution
"Transverse" Charged PTsum Distribution
1.0E+00
1.0E+00
CMS Preliminary
1.0E-01
1.0E-01
1.0E-02
CMS
1.0E-02
7 TeV
1.0E-03
900 GeV
CMS Preliminary
PT(chgjet#1) > 3 GeV/c
data uncorrected
Theory + SIM
Probability
Probability
PT(chgjet#1) > 3 GeV/c
D6T
1.0E-04
data uncorrected
pyZ1+ SIM
CMS
Tune Z1
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
on the charged scalar PTsum distribution in
on the charged scalar PTsum distribution in
the “transverse” region for charged particles
the “transverse” region for charged particles
(pT > 0.5 GeV/c, |h| < 2) as defined by the
(pT > 0.5 GeV/c, |h| < 2) as defined by the
leading charged particle jet with
leading charged particle jet with
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).
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 45
“Transverse” Multiplicity Distribution
"Transverse" Charged Particle Multiplicity
"Transverse" Charged Particle Multiplicity
1.0E+00
1.0E+00
7 TeV
7 TeV
CMS Preliminary
data uncorrected
Theory + SIM
1.0E-01
1.0E-01
CMS
1.0E-02
CMS
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
 CMS uncorrected data at 7 TeV on the
 CMS uncorrected data at 7 TeV on the
charged particle multiplicity distribution in
charged particle multiplicity distribution in
the “transverse” region for charged particles the “transverse” region for charged particles
(pT > 0.5 GeV/c, |h| < 2) as defined by the
(pT > 0.5 GeV/c, |h| < 2) as defined by the
leading charged particle jet with PT(chgjet#1) leading charged particle jet with PT(chgjet#1)
> 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).
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 46
“Transverse” Multiplicity Distribution
"Transverse" Charged Particle Multiplicity
1.0E+00
7 TeV
PT(chgjet#1) Direction
CMS Preliminary
Difficult to produce
enough events with
large “transverse”
multiplicity at low
hard scale!
data uncorrected
pyZ1 + SIM
1.0E-01
f
Tune Z1
1.0E-02
“Toward”
“Transverse”
“Transverse”
“Away”
Probability
PT(chgjet#1) > 20 GeV/c
1.0E-03
CMS
1.0E-04
PT(chgjet#1) > 3 GeV/c
1.0E-05
Normalized to 1
1.0E-06
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-07
0
5
10
15
20
25
30
35
40
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 Z1 at the detector level (i.e. Theory + SIM).
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 47
“Transverse” PTsum Distribution
"Transverse" Charged PTsum Distribution
"Transverse" Charged PTsum Distribution
1.0E+00
1.0E+00
7 TeV
data uncorrected
Theory + SIM
1.0E-01
1.0E-01
CMS
1.0E-02
CMS Preliminary
1.0E-03
PT(chgjet#1) > 3 GeV/c
1.0E-04
data uncorrected
pyZ1 + SIM
CMS
1.0E-02
PT(chgjet#1) > 20 GeV/c
Probability
Probability
7 TeV
CMS Preliminary
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
PTsum distribution in the “transverse” region for
PTsum distribution in the “transverse” region
charged particles (pT > 0.5 GeV/c, |h| < 2) as
for charged particles (pT > 0.5 GeV/c, |h| < 2)
defined by the leading charged particle jet with
as defined by the leading charged particle jet
PT(chgjet#1) > 3 GeV/c and PT(chgjet#1) > 20
with PT(chgjet#1) > 3 GeV/c and PT(chgjet#1)
GeV/c compared with 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).
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 48
“Transverse” PTsum Distribution
"Transverse" Charged PTsum Distribution
1.0E+00
7 TeV
PT(chgjet#1) Direction
CMS Preliminary
f
Tune Z1
“Transverse”
“Transverse”
Probability
1.0E-02
“Toward”
Difficult to produce
enough events with
large “transverse”
PTsum at low hard
scale!
data uncorrected
pyZ1 + SIM
1.0E-01
PT(chgjet#1) > 20 GeV/c
1.0E-03
PT(chgjet#1) > 3 GeV/c
CMS
1.0E-04
“Away”
Normalized to 1
1.0E-05
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-06
0
5
10
15
20
25
30
35
40
45
50
PTsum (GeV/c)
 CMS uncorrected data at 7 TeV on the charged PTsum 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 Z1 at the detector level (i.e. Theory + SIM).
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 49
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.
Okay not perfect, but remember
we do not know if the DD is correct!
ECT* - QCD at the LHC
Trento September 28, 2010
3.0
Rick Field – Florida/CDF/CMS
Page 50
PYTHIA Tune Z1
If one increases the
hard scale the
agreement improves!
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.
Okay not perfect, but remember
we do not know if the SD & DD are correct!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 51
NSD Multiplicity Distribution
Charged Multiplicity Distribution
1.0E-01
RDF Preliminary
7 TeV
data CMS NSD
generator level theory
CMS
Probability
1.0E-02
Difficult to produce
enough events with
large multiplicity!
Tune Z1
1.0E-03
CMS Data (24.6)
pyZ1 HC (26.8)
pyZ1 NSD (23.0)
Charged Particles
(all PT, |h|<2.0)
1.0E-04
0
20
40
60
80
100
Number of Charged Particles
 Generator level charged multiplicity distribution (all pT, |h| < 2) at 7 TeV. Shows
the NSD = HC + DD and the HC = ND contributions for Tune Z1. Also shows the
CMS NSD data.
Okay not perfect!
But not that bad!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 52
NSD <pT> versus Nchg
Average PT versus Nchg
Average PT versus Nchg
0.7
CMS Preliminary
CMS Preliminary
data corrected
generator level theory
data corrected
generator level theory
0.6
0.5
CMS
0.4
CMS 7 TeV |eta| < 2.4
CMS 7 TeV <pT>=0.545
pyZ1 NSD LHC7
pyZ1 NSD LHC7 <pT>=0.577
7 TeV
Charged Particles (|h|<2.4, All pT)
0.3
Average PT (GeV/c)
Average PT (GeV/c)
0.7
0.6
CMS 900 GeV |eta| < 2.4
CMS 900 GeV <pT>=0.460
pyZ1 NSD LHC09
pyZ1 LHC09 <pT>=0.489
0.5
CMS
0.4
900 GeV
Charged Particles (|h|<2.4, All pT)
0.3
0
10
20
30
40
50
60
70
80
90 100 110 120 130 140 150
0
10
20
Number of Charged Particles
30
40
50
60
70
80
90 100 110 120 130 140 150
Number of Charged Particles
Shows the 7 TeV and 900 GeV CMS NSD corrected data on <pT> versus
Nchg (all pT, |h| < 2.4) compared with Tune Z1.
Okay not perfect!
But not that bad!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 53
<pT> versus Nchg
Ratio: Average PT versus Nchg
Ratio: Average PT versus Nchg
1.3
CMS Preliminary
CMS Preliminary
Charged Particles (|h|<2.4, All pT)
data corrected
generator level theory
Ratio: 7 TeV / 900 GeV
Ratio: 7 TeV / 900 GeV
1.3
1.2
1.1
CMS Ratio |eta| < 2.4
1.0
CMS Ratio = 1.185
7 TeV / 900 GeV
5
10
15
20
Tune PQ20
1.1
1.0
7 TeV / 900 GeV
pyX1844 Ratio = 1.194
25
30
35
40
45
50
55
60
Tune P0
Tune P329
1.2
pyX1844_10mm NSD Ratio
0.9
0
data corrected
generator level theory
Charged Particles (|h|<2.4, All pT)
0.9
65
0
5
10
Number of Charged Particles
15
20
25
30
35
40
45
50
55
60
65
Number of Charged Particles
 (left) Shows the energy dependence of the CMS NSD corrected data on <pT> versus
Nchg (all pT, |h| < 2.4) compared with Tune X2. Also shows the energy dependence
of the overall <pT> compared with Tune X2.
 (right) Shows the energy dependence of the CMS NSD corrected data on <pT> versus
Nchg (all pT, |h| < 2.4) compared with Tune P0, Tune PQ20, and Tune P329. It will
be interesting to see if any tune can get this right!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 54
NSD <pT> versus Nchg
Ratio: Average PT versus Nchg
Ratio: 7 TeV / 900 GeV
1.3
Amazing!
CMS Preliminary
Charged Particles (|h|<2.4, All pT)
data corrected
generator level theory
1.2
1.1
CMS Ratio |eta| < 2.4
1.0
CMS Ratio = 1.185
7 TeV / 900 GeV
pyZ1 NSD Ratio
0.9
pyZ1 Ratio = 1.149
0
5
10
15
20
25
30
35
40
45
50
55
60
65
Number of Charged Particles
 Shows the energy dependence of the CMS NSD corrected data on <pT> versus Nchg
(all pT, |h| < 2.4) compared with Tune Z1. Also shows the energy dependence of the
overall <pT> compared with Tune Z1.
First Tune (except PhoJet)
to come close here!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 55
NSD Multiplicity Distribution
Charged Multiplicity Distribution
1.0E-01
RDF Preliminary
data CMS NSD
pyZ1 generator level
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.
Okay not perfect!
But not that bad!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 56
NSD Multiplicity Distribution
"Transverse" Charged Particle Multiplicity
Charged Multiplicity Distribution
1.0E+00
1.0E-01
RDF Preliminary
“Min-Bias”
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
1.0E-06
Charged Particles
(all PT, |h|<2.0)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Tune Z1
1.0E-07
1.0E-04
0
20
40
60
80
0
100
10
15
20
25
30
35
40
Number of Charged Particles
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.
ECT* - QCD at the LHC
Trento September 28, 2010
5
 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 Z1 at the
detector level (i.e. Theory + SIM).
Rick Field – Florida/CDF/CMS
Page 57
PYTHIA Tune Z1
Charged Particle Multiplicity
1.0E+00
CMS
7 TeV
Tune Z1
Min-Bias
NSD All pT
1.0E-01
Probability
CMS Preliminary
1.0E-02
1.0E-03
Underlying Event
"Transverse" Region
pT > 0.5 GeV/c
PT(chgjet#1) > 20 GeV/c
1.0E-04
Normalized to 1
Tune Z1
Charged Particles (|h|<2.0)
1.0E-05
0
5
10
15
20
25
30
35
40
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 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!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 58
PYTHIA Tune Z1
Charged Particle Multiplicity
1.0E+00
CMS
7 TeV
CMS Preliminary
Tune Z1
Tune Z1
1.0E-01
Probability
Min-Bias
NSD All pT
1.0E-02
1.0E-03
1.0E-04
Underlying Event
"Transverse" Region
pT > 0.5 GeV/c
PT(chgjet#1) > 20 GeV/c
Normalized to 1
Charged Particles (|h|<2.0)
1.0E-05
0
20
40
60
80
100
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 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!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 59
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/p ratio fairly independent of the center-of-mass energy.
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 60
Strange Baryon Production
More strange baryons than expected!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 61
Long-Range Same-Side
Correlations
High Multiplicity “Min-Bias”
Not there in PYTHIA8!
ECT* - QCD at the LHC
Trento September 28, 2010
High Multiplicity “Min-Bias”
Also not there in PYTHIA 6 and HERWIG++!
Rick Field – Florida/CDF/CMS
Page 62
Long-Range Same-Side
Correlations
High Multiplicity “Min-Bias”
High Multiplicity “Min-Bias”
New type of “underlying event”! Would like to remove all the ordinary QCD
jets and MPI from the event and look for a long range collective phenomena!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 63
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!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 64
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 h)
correlation with f ≈ 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?
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 65
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?
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 66
MPI Correlations?
MPI
Correlations
z-axis
 Large multiplicity implies a large number
of multiple-parton interactions (MPI).
Maybe there are MPI correlations (i.e.
prefer to lie in a plane)?
??
 In the current MPI models the
individual MPI are not correlated!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 67
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
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 68
Min-Bias Summary
We need a better understanding and modeling of diffraction!
Explore by defining “diffractive enhanced” data samples!
Best
Bad
Good
See the talk by Lauren Tompkins at the LPCC MB&UE@LHC Meeting September 6, 2010,
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 69
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
Here it is important to study both the
Connections
absolute rate (i.e. cross section and
the
ratios K/p or K/(all charged) etc.!
ECT* - QCD at the LHC
Trento September 28, 2010
Rick Field – Florida/CDF/CMS
Page 70