Predicting “Min-Bias” and the
“Underlying Event” at the LHC
Important 900 GeV Measurements
Rick Field
University of Florida
Outline of Talk
The inelastic non-diffractive cross section.
New CDF charged multiplicity
CERN November 10, 2009
distribution and comparisons with
the QCD Monte-Carlo tunes.
Outgoing Parton
PT(hard)
Relationship between the “underlying
event” in a hard scattering process and
“min-bias” collisions.
Initial-State Radiation
CDF Run 2
“Min-Bias at 900 GeV and 2.2 TeV.
Proton
Proton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
The “underlying event” at 900 GeV
and 7 TeV.
Summary.
CMS-QCD Group Meeting
November 10, 2009
CMS at the LHC
Rick Field – Florida/CDF/CMS
UE&MB@CMS
Page 1
Inelastic Non-Diffractive Cross-Section
Inelastic Non-Diffractive Cross-Section: σHC
Inelastic Non-Diffractive Cross-Section: σHC
70
70
RDF Preliminary
60
py Tune DW generator level
Cross-Section (mb)
Cross-Section (mb)
60
50
40
My guess!
30
20
10
RDF Preliminary
py Tune DW generator level
50
40
30
20
10
K-Factor = 1.2
K-Factor = 1.2
0
0
0
2
4
6
8
10
12
14
0.1
1.0
Center-of-Mass Energy (TeV)
Linear scale!
10.0
100.0
Center-of-Mass Energy (TeV)
Log scale!
σtot = σEL + σSD + σDD + σHC
The inelastic non-diffractive cross section versus center-of-mass energy from PYTHIA (×1.2).
σ
σHC varies slowly.
Only a 13% increase between 7 TeV (≈ 58 mb) and 14 teV (≈ 66 mb).
Linear on a log scale!
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 2
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
1.0E+00
CDF Run 2 Preliminary
CDF Run 2 Preliminary
1.0E-01
1.0E-01
CDF Run 2 <Nchg>=4.5
CDF Run 2 <Nchg>=4.5
1.0E-02
1.0E-02
1.0E-03
1.0E-03
py64 Tune A <Nchg> = 4.1
Probability
Probability
pyAnoMPI <Nchg> = 2.6
1.0E-04
1.0E-05
1.0E-04
1.0E-05
1.0E-06
1.0E-06
HC 1.96 TeV
Min-Bias 1.96 TeV
1.0E-07
1.0E-07
η|<1.0, PT>0.4 GeV/c)
Normalized to 1 Charged Particles (|η
Normalized to 1
Charged Particles (|η
η|<1.0, PT>0.4 GeV/c)
1.0E-08
1.0E-08
0
5
10
15
20
25
30
35
40
45
50
55
0
5
20
25
30
35
40
No MPI!
“Minumum Bias” Collisions
Proton
15
45
50
55
Number of Charged Particles
Number of Charged Particles
7 decades!
10
Tune A!
AntiProton
Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |η
η| < 1) for “min-bias”
collisions at CDF Run 2.
The data are compared with PYTHIA Tune A and Tune A without multiple parton
interactions (pyAnoMPI).
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 3
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
0.20
1.0E+00
CDF Run 2 Preliminary
0.15
CDF Run 2 <Nchg>=4.5
py64 Tune A <Nchg> = 4.1
1.0E-02
pyAnoMPI <Nchg> = 2.6
0.10
Probability
Probability
CDF Run 2 Preliminary
1.0E-01
CDF Run 2 <Nchg>=4.5
Charged Particles (|η
η|<1.0, PT>0.4 GeV/c)
HC 1.96 TeV
0.05
Normalized to 1
0.00
0
2
4
6
8
10
12
14
Number of Charged Particles
16
pyS320 <Nchg> = 4.2
1.0E-03
1.0E-04
1.0E-05
1.0E-06
HC 1.96 TeV
1.0E-07
Normalized to 1 Charged Particles (|η|<1.0, PT>0.4 GeV/c)
η
1.0E-08
0
5
Tune A!
No MPI!
10
15
20
25
30
35
40
45
50
55
Number of Charged Particles
“Minumum Bias” Collisions
Proton
Tune S320!
AntiProton
Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |η
η| < 1) for “min-bias”
collisions at CDF Run 2.
The data are compared with PYTHIA Tune A and Tune A without multiple parton
interactions (pyAnoMPI).
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 4
Charged Particle Multiplicity
Charged Multiplicity DistributionCharged
0.20
1.0E+00
0.20
CDF Run 2 Preliminary
CDF
1.0E-01
CDF Run 2 <Nchg>=4.5
0.15
py64 Tune A <Nchg> = 4.1
0.15
HC 1.96 TeV
0.05
Normalized to 1
0
2
4
CDF Run 2 Preliminary
CDF Run 2 <Nchg>=4.5
CDF Run 2 <Nchg>=4.5
pyS320 <Nchg> = 4.2
py64 Tune A <Nchg> = 4.1
Charged Particles (|η
η|<1.0, PT>0.4 GeV/c)
0.10
HC 1.96 TeV
0.05
0.00
Run 2 Preliminary
1.0E-02
pyAnoMPI <Nchg> = 2.6
Probability
0.10
Probability
Probability
Charged Multiplicity Distribution
Multiplicity Distribution
1.0E-03
py64DW <Nchg> = 4.2
1.0E-04
pyS320 <Nchg> = 4.2
pyP329 <Nchg> = 4.4
1.0E-05
1.0E-06
Normalized
to 1 14
12
16
Charged
Particles (|η
η|<1.0, PT>0.4 GeV/c)
Number of Charged
Particles
1.0E-07
6
8
10
HC 1.96 TeV
Normalized to 1 Charged Particles (|η|<1.0, PT>0.4 GeV/c)
η
0.00
0
2
4
6
8 1.0E-08 10
0
12
5
Tune A!Number of Charged Particles
No MPI!
10
14
15
20
16
25
30
35
40
45
50
55
Number of Charged Particles
“Minumum Bias” Collisions
Proton
Tune S320!
AntiProton
Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |η
η| < 1) for “min-bias”
collisions at CDF Run 2.
The data are compared with PYTHIA Tune A and Tune A without multiple parton
interactions (pyAnoMPI).
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 5
The “Underlying Event”
Select inelastic non-diffractive events
that contain a hard scattering
Proton
Hard parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
The “underlying-event” (UE)!
Proton
Given that you have one hard
scattering it is more probable to
have MPI! Hence, the UE has
more activity than “min-bias”.
CMS-QCD Group Meeting
November 10, 2009
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 6
The Inelastic Non-Diffractive
Cross-Section
Occasionally one of
the parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
Proton
Majority of “minbias” events!
Proton
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
+
Proton
+
Proton
Proton
Proton
+
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 7
The “Underlying Event”
Select inelastic non-diffractive events
that contain a hard scattering
Proton
Hard parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
The “underlying-event” (UE)!
Proton
Given that you have one hard
scattering it is more probable to
have MPI! Hence, the UE has
more activity than “min-bias”.
CMS-QCD Group Meeting
November 10, 2009
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 8
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
1.0E+00
CDF Run 2 Preliminary
CDF Run 2 Preliminary
1.0E-01
1.0E-01
CDF Run 2 <Nchg>=4.5
py64 Tune A <Nchg> = 4.1
pyA 900 GeV <Nchg> = 3.3
py64A LHC22 <Nchg> = 4.1
CDF Run 2 <Nchg>=4.5
1.0E-02
1.0E-02
py64 Tune A <Nchg> = 4.1
1.0E-03
Probability
Probability
pyAnoMPI <Nchg> = 2.6
1.0E-04
1.0E-05
1.0E-03
1.0E-04
1.0E-05
1.0E-06
1.0E-06
HC 1.96 TeV
Min-Bias
1.0E-07
1.0E-07
Normalized to 1
Normalized to 1
Charged Particles (|η
η|<1.0, PT>0.4 GeV/c)
Charged Particles (|η
η|<1.0, PT>0.4 GeV/c)
1.0E-08
1.0E-08
0
5
10
15
20
25
30
35
40
45
50
55
Number of Charged Particles
No MPI!
“Minumum Bias” Collisions
Proton
Tune A!
0
5
10
Tune A prediction at
900 GeV!
15
20
25
30
35
40
45
50
55
Number of Charged Particles
TuneCollisions
A prediction
“Minumum Bias”
at
2.2 TeV!
AntiProton
Proton
Proton
Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |η
η| < 1) for “min-bias”
collisions at CDF Run 2. The data are compared with PYTHIA Tune A and Tune A without
multiple parton interactions (pyAnoMPI).
Prediction from PYTHIA Tune A for proton-proton collisions at 900 GeV and 2.2 TeV.
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 9
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
1.0E+00
CDF Run 2 Preliminary
CDF Run 2 Preliminary
1.0E-01
1.0E-01
CDF Run 2 <Nchg>=4.5
py64 Tune A <Nchg> = 4.1
pyA 900 GeV <Nchg> = 3.3
py64A LHC22 <Nchg> = 4.1
CDF Run 2 <Nchg>=4.5
1.0E-02
1.0E-02
py64 Tune A <Nchg> = 4.1
1.0E-03
Probability
Probability
pyAnoMPI <Nchg> = 2.6
1.0E-04
1.0E-05
1.0E-03
The charged multiplicity distribution
does not change between
1.96 and 2.2 TeV
and proton-proton is the same as
Tune A prediction at
proton-antiproton!
900 GeV!
1.0E-04
1.0E-05
1.0E-06
1.0E-06
HC 1.96 TeV
Min-Bias
1.0E-07
1.0E-07
Normalized to 1
Normalized to 1
Charged Particles (|η
η|<1.0, PT>0.4 GeV/c)
Charged Particles (|η
η|<1.0, PT>0.4 GeV/c)
1.0E-08
1.0E-08
0
5
10
15
20
25
30
35
40
45
50
55
0
“Minumum Bias” Collisions
Proton
10
15
20
25
30
35
40
45
50
55
Number of Charged Particles
Number of Charged Particles
No MPI!
5
TuneCollisions
A prediction
“Minumum Bias”
Tune A!
at
2.2 TeV!
AntiProton
Proton
Proton
Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |η
η| < 1) for “min-bias”
collisions at CDF Run 2. The data are compared with PYTHIA Tune A and Tune A without
multiple parton interactions (pyAnoMPI).
Prediction from PYTHIA Tune A for proton-proton collisions at 900 GeV and 2.2 TeV.
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 10
LHC Predictions: 900 GeV
Charged Multiplicity Distribution
Charged Multiplicity Distribution
0.08
1.0E+00
RDF Preliminary
RDF Preliminary
Charged Particles (|η
η|<2.0)
1.0E-01
Probability
1.0E-02
Probability
pyA 900 GeV <Nchg> = 14.2
pyDW 900 GeV <Nchg> = 14.4
pyS320 900 GeV <Nchg> = 14.2
pyP329 900 GeV <Nchg> = 14.7
0.06
All pT
<Nchg> ~ 14
1.0E-03
0.04
0.02
pT > 0.5 geV/c
<Nchg> ~ 5
HC 900 GeV
Charged Particles (|η
η|<2.0, all pT)
Normalized to 1
1.0E-04
0.00
0
HC 900 GeV
5
1.0E-05
10
15
20
25
30
35
40
Number of Charged Particles
Normalized to 1
1.0E-06
0
10
20
30
40
50
60
70
80
Number of Charged Particles
“Minumum Bias” Collisions
“Minumum Bias” Collisions
Proton
Proton
Proton
Proton
Charged multiplicity distributions for proton-proton collisions at 900 GeV
(|η
η| < 2) from PYTHIA Tune A, Tune DW, Tune S320, and Tune P329.
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 11
LHC Predictions: 900 GeV
Charged Multiplicity
Multiplicity Distribution
Distribution
Charged
Charged Multiplicity Distribution
0.08
0.16
1.0E+00
RDF Preliminary
1.0E-01
pyDW
900
GeV<Nchg>
<Nchg>== 14.2
5.3
pyA
900
GeV
pyDW
14.4
pyS320900
900GeV
GeV<Nchg>
<Nchg> == 5.2
pyS320
900 GeV
GeV<Nchg>
<Nchg>
= 14.2
pyP329 900
= 5.3
pyP329 900 GeV <Nchg> = 14.7
Probability
Probability
0.06
0.12
1.0E-02
Probability
RDF
Preliminary
pyA <Nchg>
= 5.0 STdev = 4.5
RDF Preliminary
Charged Particles (|η
η|<2.0)
All pT
<Nchg> ~ 14
1.0E-03
0.04
0.08
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.02
0.04
pT > 0.5 geV/c
<Nchg> ~ 5
HC HC
900900
GeVGeV
Normalized
to 1 to 1
Normalized
1.0E-04
Charged Particles (|η
η|<2.0, all pT)
0.00
0.00
00
HC 900 GeV
25
1.0E-05
10
4
15
6
20
8
25
10
30
12
35
14
40
16
Number of
of Charged
Charged Particles
Particles
Number
Normalized to 1
1.0E-06
0
10
20
30
40
50
60
70
80
Number of Charged Particles
“Minumum Bias” Collisions
“Minumum Bias” Collisions
Proton
Proton
Proton
Proton
Charged multiplicity distributions for proton-proton collisions at 900 GeV
(|η
η| < 2) from PYTHIA Tune A, Tune DW, Tune S320, and Tune P329.
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 12
LHC Predictions: 900 GeV
Charged Multiplicity
Multiplicity Distribution
Distribution
Charged
Charged Multiplicity Distribution
Charged Transverse Momentum
Distribution
0.08
0.16
1.0E+00
RDF Preliminary
1.0E+02
py64DW <Nchg> = 14.4 <pT> = 787 MeV/c
1.0E-01
pyS320 <Nchg> = 14.2 <pT> = 778 MeV/c
Probability
Probability
1.0E-03
d<Nchg>/dpT 1/(GeV/c)
0.06
0.12
1.0E-02
Probability
RDF
Preliminary
pyA <Nchg>
= 5.0 STdev = 4.5
RDF Preliminary
Charged Particles (|η
η|<2.0)
1.0E+01
pyP329 <Nchg> = 14.7 <pT> = 795 MeV/c
All pT
<Nchg> ~ 14
1.0E+00
HC 900 GeV
1.0E-05
RDF Preliminary
1.0E-06
0
10
20
HC HC
900900
GeVGeV
Normalized
to 1 to 1
Normalized
Charged Particles (|η
η|<2.0, all pT)
0.00
0.00
00
1.0E-02
HC 900 GeV
Normalized to 1
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.02
0.04
pT > 0.5 geV/c
<Nchg> ~ 5 1.0E-01
1.0E-04
0.04
0.08
pyDW
900
GeV<Nchg>
<Nchg>== 14.2
5.3
pyA
900
GeV
pyDW
14.4
pyS320900
900GeV
GeV<Nchg>
<Nchg> == 5.2
pyS320
900 GeV
GeV<Nchg>
<Nchg>
= 14.2
pyP329 900
= 5.3
pyP329 900 GeV <Nchg> = 14.7
25
10
4
15
6
20
8
25
10
30
12
35
14
40
16
Number of Charged Particles
Charged Particles (|η
η|<2.0) Number of Charged Particles
1.0E-03
30
0.0
40
50
1.0
60
Number of Charged Particles
70
802.0
3.0
4.0
5.0
Transverse Momentum (GeV/c)
“Minumum Bias” Collisions
“Minumum Bias” Collisions
Proton
Proton
Proton
Proton
Charged multiplicity distributions for proton-proton collisions at 900 GeV
(|η
η| < 2) from PYTHIA Tune A, Tune DW, Tune S320, and Tune P329.
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 13
LHC Predictions: 900 GeV
Charged Multiplicity Distribution
Charged Multiplicity Distribution
Charged Multiplicity Distribution
Charged Transverse
Transverse Momentum
Momentum
Distribution
Charged
Distribution
0.08
0.16
1.0E+00
RDF Preliminary
30
1.0E+02
py64DW <Nchg> = 14.4 <pT> = 787 MeV/c
RDF
0.06
0.12
1.0E+01
py64DW
<Nchg>==14.7
14.4<pT>
<pT>==795
787MeV/c
MeV/c
pyP329 <Nchg>
20
1.0E+00
HC 900 GeV
1.0E-05
Normalized to 1
1.0E-06
0
10
20
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
pyP329 <Nchg> = 14.7 <pT> = 795 MeV/c
0.02
0.04
HC HC
900900
GeVGeV
Charged Particles (|η
η|<2.0)
10
Normalized
to 1 to 1
Normalized
RDF Preliminary
00
HC 900
HC GeV
900 GeV
0
1.0E-03
0.0 0.0 0.2
40
50
0.4
1.0
60
Number of Charged Particles
70
0.6
Charged Particles (|η
η|<2.0, all pT)
0.00
0.00
1.0E-02
30
0.04
pyDW
900
GeV<Nchg>
<Nchg>== 14.2
5.3
pyA
900
GeV
pyDW
14.4
pyS320900
900GeV
GeV<Nchg>
<Nchg> == 5.2
pyS320
900 GeV
GeV<Nchg>
<Nchg>
= 14.2
pyP329 900
= 5.3
pyP329 900 GeV <Nchg> = 14.7
0.08
pyS320
<Nchg> = 14.2 <pT> = 778 MeV/c
All pT
<Nchg> ~ 14
pT > 0.5 geV/c
<Nchg> ~ 5 1.0E-01
1.0E-04
Preliminary
pyS320 <Nchg> = 14.2 <pT> = 778 MeV/c
Probability
Probability
Probability
1.0E-03
d<Nchg>/dpT
d<Nchg>/dpT1/(GeV/c)
1/(GeV/c)
1.0E-01
1.0E-02
RDF
Preliminary
pyA <Nchg>
= 5.0 STdev = 4.5
RDF Preliminary
Charged Particles (|η
η|<2.0)
25
10
4
15
6
20
8
25
10
30
12
35
14
40
16
Number of Charged Particles
Charged Particles (|η
η|<2.0) Number of Charged Particles
802.0
0.8
1.0
3.0
1.2 4.0 1.4
1.6
5.0
Transverse
Momentum
(GeV/c)
Transverse
Momentum
(GeV/c)
“Minumum Bias” Collisions
“Minumum Bias” Collisions
Proton
Proton
Proton
Proton
Charged multiplicity distributions for proton-proton collisions at 900 GeV
(|η
η| < 2) from PYTHIA Tune A, Tune DW, Tune S320, and Tune P329.
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 14
“Transverse” Charged Density
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
"Transverse" Charged Particle Multiplicity
0.18
RDF Preliminary
generator level
py64DW <Nchg> = 3.5 <NchgDen> = 0.42
pyS320 <Nchg> = 3.4 <NchgDen> = 0.41
pyDW
0.4
Probability
"Transverse" Charged Density
0.6
pyS320
0.2
0.12
RDF Preliminary
generator level
0.06
HC 900 GeV PTmax > 5 GeV/c
HC 900 GeV
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.0
0.00
0
2
4
6
8
10
12
14
16
18
20
0
1
PTmax (GeV/c)
2
3
4
5
6
8
9
10
11
12
13
14
Number of Charged Particles
PTmax Direction
PTmax Direction
∆φ
∆φ
“Toward”
“Transverse”
7
“Toward”
“Transverse”
“Transverse”
“Away”
“Transverse”
PTmax > 5 GeV/c!
“Away”
Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, |η
η| < 2) at 900 GeV as defined by PTmax from PYTHIA Tune DW and Tune S320 at the
particle level (i.e. generator level).
Shows the charged particle multiplicity distribution in the “transverse” region (pT > 0.5 GeV/c,
|η
η| < 2) at 900 GeV as defined by PTmax from PYTHIA Tune DW and Tune S320 at the particle
level (i.e. generator level).
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 15
Charged Particle Multiplicity
NchgDen = 0.21
The “underlying event” is twice as
active as an average HC collision!
Charged Multiplicity Distribution
"Transverse" Charged Particle Multiplicity
0.18
0.16
RDF Preliminary
py64DW <Nchg> = 3.5 <NchgDen> = 0.42
pyA <Nchg> = 5.0 STdev = 4.5
pyDW 900 GeV <Nchg> = 5.3
pyS320 <Nchg> = 3.4 <NchgDen> = 0.41
0.12
Probability
Probability
0.12
RDF Preliminary
generator level
0.06
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
2
3
4
5
6
0.08
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
7
HC 900 GeV
Normalized to 1
0.00
0.00
1
pyP329 900 GeV <Nchg> = 5.3
0.04
HC 900 GeV PTmax > 5 GeV/c
0
pyS320 900 GeV <Nchg> = 5.2
8
9
10
11
12
13
14
0
2
4
6
8
10
12
14
16
Number of Charged Particles
Number of Charged Particles
PTmax Direction
∆φ
“Toward”
“Transverse”
“Minumum Bias” Collisions
Proton
Proton
“Transverse”
“Away”
Shows the charged particle multiplicity distribution in the “transverse” region (pT > 0.5 GeV/c,
|η
η| < 2) at 900 GeV as defined by PTmax from PYTHIA Tune DW and Tune S320 at the particle
level (i.e. generator level).
Shows the charged particle multiplicity distribution in HC collisions (pT > 0.5 GeV/c, |η
η| < 2) at
900 GeV PYTHIA Tune A, Tune DW, Tune S320, and Tune P329 at the particle level (i.e.
generator level).
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 16
σHC: PTmax > 5 GeV/c
Inelastic HC Cross-Section: PTmax > 5 GeV/c
Inelastic HC Cross-Section: PTmax > 5 GeV/c
1.6
RDF Preliminary
RDF Preliminary
py Tune DW generator level
py Tune DW generator level
Cross-Section (mb)
Cross-Section (mb)
1.5
K-Factor = 1.2
1.0
0.5
1.2
K-Factor = 1.2
Charged Particles (PTmax > 5 GeV/c |η
η| < 1)
0.8
0.4
Charged Particles (PTmax > 5 GeV/c |η
η| < 1)
0.0
0.0
0
2
4
6
8
10
12
14
0.1
1.0
10.0
100.0
Center-of-Mass Energy (TeV)
Center-of-Mass Energy (TeV)
Log scale!
Linear scale!
σtot = σEL + σSD + σDD + σHC
The inelastic non-diffractive PTmax > 5 GeV/c cross section (|η
η| < 1) versus center-of-mass
energy from PYTHIA (×1.2).
σ
σHC(PTmax > 5 GeV/c) varies more rapidly. Factor of 2.3 increase between 7 TeV (≈ 0.56 mb)
and 14 teV (≈ 1.3 mb). Linear on a linear scale!
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 17
σHC: PTmax > 5 GeV/c
Inelastic HC Cross-Section: PTmax > 5 GeV/c
Inelastic HC Cross-Section: PTmax > 5 GeV/c
Number
of Events Fraction
in 1/nb: PTmax
>>55GeV/c
HC
Cross-Section:
PTmax
GeV/c
1.6
1.5
1,500,000
2.0%
py Tune DW generator level
py Tune
generator
level level
py DW
Tune
DW generator
K-Factor = 1.2
1.0
0.5
0.0
0
2
Percent
Numberof
ofEvents
Events
Cross-Section (mb)
RDF Preliminary
RDF RDF
Preliminary
Preliminary
1.5%
1,000,000
K-Factor = 1.2
Still lots of events!
1.0%
Cross-Section (mb)
RDF Preliminary
py Tune DW generator level
1.2
K-Factor = 1.2
Charged Particles (PTmax > 5 GeV/c |η
η| < 1)
0.8
0.4
500,000
Charged Particles (PTmax > 5 GeV/c |η
η| < 1)
0.5%
4
0.0
6
8
10
12
0.1
1.0
10.0
100.0
Charged Particles (PTmax > 5 GeV/c
|η
η| < 1)
Center-of-Mass
Energy (TeV)
Center-of-Mass Energy (TeV)
0
0.0%
0
Linear scale!
14
0
2
2
4
4
6 6
88
10
10
Log scale!
12
12
14
14
Center-of-Mass
Energy
(TeV)
Center-of-Mass
Energy
(TeV)
σtot = σEL + σSD + σDD + σHC
In 1,000,000 HC collisions at
900 GeV you get 940 with
PTmax > 5 GeV/c!
The inelastic non-diffractive PTmax > 5 GeV/c cross section (|η
η| < 1) versus center-of-mass
energy from PYTHIA (×1.2).
σ
σHC(PTmax > 5 GeV/c) varies more rapidly. Factor of 2.3 increase between 7 TeV (≈ 0.56 mb)
and 14 teV (≈ 1.3 mb). Linear on a linear scale!
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 18
PTmax Cross-Section 900 GeV
σ/dPTmax
Differential Cross-Section: dσ
Number of Events with PTmax > PT0
1.0E+02
1,000,000
RDF Preliminary
pyDW 1,885 Events with PTmax > 5 GeV/c
generator level
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
1.0E+00
1.0E-01
pyS320
1.0E-02
1.0E-03
HC 900 GeV
1.0E-04
RDF Preliminary
generator level
10,000
1,000
HC 900 GeV
100
pyDW
K-Factor = 1.2
pyS320 3,160 Events with PTmax > 5 GeV/c
100,000
Number of Events
dσ/dPT (mb/GeV/c)
1.0E+01
1,000,000 HC Collisions
1.0E-05
Charged Particles (|η
η|<2.0)
10
0
2
4
6
8
10
12
14
16
18
20
0
1
2
PTmax (GeV/c)
3
4
5
6
7
8
9
10
11
12
13
14
15
PT0 (GeV/c)
σtot = σEL + σSD + σDD + σHC
In 1,000,000 HC collisions at
900 GeV you get ~3,000 with
PTmax > 5 GeV/c!
The inelastic non-diffractive PTmax > 5 GeV/c cross section (|η
η| < 2) at 900 GeV from PYTHIA
Tune DW and Tune S320.
Number of events with PTmax > PT0 (|η
η| < 2) for 1,000,000 HC collisions at 900 GeV from
PYTHIA Tune DW and Tune S320.
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 19
PTmax Cross-Section 900 GeV
σ/dPTmax
Differential Cross-Section: dσ
Number of Events with PTmax > PT0
1.0E+02
1,000,000
RDF Preliminary
pyDW 1,885 Events with PTmax > 5 GeV/c
generator level
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
1.0E+00
1.0E-01
pyS320
1.0E-02
1.0E-03
HC 900 GeV
1.0E-04
RDF Preliminary
generator level
10,000
1,000
HC 900 GeV
100
pyDW
K-Factor = 1.2
pyS320 3,160 Events with PTmax > 5 GeV/c
100,000
Number of Events
dσ/dPT (mb/GeV/c)
1.0E+01
1,000,000 HC Collisions
1.0E-05
Charged Particles (|η
η|<2.0)
10
0
2
4
6
8
10
12
14
16
18
20
0
1
2
PTmax (GeV/c)
3
4
5
6
7
8
9
10
11
12
13
14
15
PT0 (GeV/c)
σtot = σEL + σSD + σDD + σHC
In 1,000,000 HC collisions at
900 GeV you get ~3,000 with
PTmax > 5 GeV/c!
The inelastic non-diffractive PTmax > 5 GeV/c cross section (|η
η| < 2) at 900 GeV from PYTHIA
Tune DW and Tune S320.
10,000 HC
eventsGeV
with from
Number of events with PTmax > PT0 (|η
η| < 2) for 1,000,000Need
HCabout
collisions
at 900
PTmax > 5 GeV/c to do a nice analysis!
PYTHIA Tune DW and Tune S320.
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 20
PTmax Cross-Section 900 GeV
Very important to do BOTH
“soft” and “hard” physics!
σ/dPTmax
Differential Cross-Section: dσ
1.0E+02
Number of Events with PTmax > PT0
1,000,000
RDF Preliminary
pyDW 1,885 Events with PTmax > 5 GeV/c
generator level
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
1.0E+00
1.0E-01
pyS320
1.0E-02
1.0E-03
HC 900 GeV
1.0E-04
RDF Preliminary
generator level
10,000
1,000
HC 900 GeV
100
pyDW
If we get 3,400,000 HC collisions
at 900 GeV we could do both
“min-bias” AND
the “underlying event”
In 1,000,000 HC collisions at
900 GeV you get ~3,000 with
them!
σtot = σELand+ compare
σSD
PTmax+
> 5σ
GeV/c!
DD + σHC
K-Factor = 1.2
1.0E-05
pyS320 3,160 Events with PTmax > 5 GeV/c
100,000
Number of Events
dσ/dPT (mb/GeV/c)
1.0E+01
1,000,000 HC Collisions
Charged Particles (|η
η|<2.0)
10
0
2
4
6
8
10
12
14
16
18
20
0
1
PTmax (GeV/c)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
PT0 (GeV/c)
The inelastic non-diffractive PTmax > 5 GeV/c cross section (|η
η| < 2) at 900 GeV from PYTHIA
Tune DW and Tune S320.
10,000 HC
eventsGeV
with from
Number of events with PTmax > PT0 (|η
η| < 2) for 1,000,000Need
HCabout
collisions
at 900
PTmax > 5 GeV/c to do a nice analysis!
PYTHIA Tune DW and Tune S320.
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 21
Min-Bias “Associated”
Charged Particle Density
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
1.2
RDF Preliminary
14 TeV
Min-Bias
"Transverse" Charged Density
"Transverse" Charged Density
1.2
py Tune DW generator level
10 TeV
7 TeV
0.8
1.96 TeV
0.9 TeV
0.4
0.2 TeV
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
RDF Preliminary
LHC14
py Tune DW generator level
0.8
LHC10
LHC7
Tevatron
900 GeV
0.4
PTmax = 5.25 GeV/c
RHIC
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
0
25
2
PTmax Direction
“Toward”
RHIC
“Transverse”
“Transverse”
6
8
10
14
PTmax Direction
PTmax Direction
0.2 TeV → 1.96 TeV
(UE increase ~2.7 times)
Tevatron
“Away”
12
Center-of-Mass Energy (TeV)
PTmax (GeV/c)
∆φ
4
∆φ
“Toward”
“Transverse”
1.96 TeV → 14 TeV
(UE increase ~1.9 times)
LHC
∆φ
“Toward”
“Transverse”
“Transverse”
“Transverse”
“Away”
“Away”
Shows the “associated” charged particle density in the “transverse” region as a function of PTmax
for charged particles (pT > 0.5 GeV/c, |η
η| < 1, not including PTmax) for “min-bias” events at 0.2
TeV, 0.9 TeV, 1.96 TeV, 7 TeV, 10 TeV, 14 TeV predicted by PYTHIA Tune DW at the particle
Linear scale!
level (i.e. generator level).
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 22
Min-Bias “Associated”
Charged Particle Density
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
1.2
RDF Preliminary
14 TeV
Min-Bias
"Transverse" Charged Density
"Transverse" Charged Density
1.2
py Tune DW generator level
10 TeV
7 TeV
0.8
1.96 TeV
0.9 TeV
0.4
0.2 TeV
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
RDF Preliminary
py Tune DW generator level
LHC14
LHC10
LHC7
0.8
Tevatron
0.4
900 GeV
RHIC
PTmax = 5.25 GeV/c
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
0.1
1.0
PTmax Direction
PTmax Direction
“Toward”
LHC7
“Transverse”
∆φ
7 TeV → 14 TeV
(UE increase ~20%)
“Toward”
LHC14
“Transverse”
“Away”
100.0
Center-of-Mass Energy (TeV)
PTmax (GeV/c)
∆φ
10.0
Linear on a log plot!
“Transverse”
“Transverse”
“Away”
Shows the “associated” charged particle density in the “transverse” region as a function of PTmax
for charged particles (pT > 0.5 GeV/c, |η
η| < 1, not including PTmax) for “min-bias” events at 0.2
TeV, 0.9 TeV, 1.96 TeV, 7 TeV, 10 TeV, 14 TeV predicted by PYTHIA Tune DW at the particle
Log scale!
level (i.e. generator level).
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 23
“Transverse” Charge Density
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
"Transverse" Charged Particle Density: dN/dη
1.2
"Transverse" Charged Density
"Transverse" Charged Density
0.6
RDF Preliminary
generator level
pyDW
0.4
pyS320
0.2
HC 900 GeV
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
RDF Preliminary
py Tune DW generator level
7 TeV
0.8
factor of 2!
900 GeV
0.4
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.0
0.0
0
2
4
6
8
10
12
14
16
18
20
0
2
4
6
8
10
PTmax (GeV/c)
“Toward”
LHC
900 GeV
“Transverse”
14
16
18
20
PTmax Direction
PTmax Direction
∆φ
12
PTmax (GeV/c)
900 GeV → 7 TeV
(UE increase ~ factor of 2.1)
“Transverse”
“Away”
∆φ
“Toward”
LHC
7 TeV
“Transverse”
“Transverse”
“Away”
Shows the charged particle density in the “transverse” region for charged particles (pT > 0.5
GeV/c, |η
η| < 2) at 900 GeV as defined by PTmax from PYTHIA Tune DW and Tune S320 at the
particle level (i.e. generator level).
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 24
Important 900 GeV Measurements
“Minumum Bias” Collisions
Charged Multiplicity Distribution
0.08
Proton
Proton
RDF Preliminary
pyA 900 GeV <Nchg> = 14.2
pyDW 900 GeV <Nchg> = 14.4
pyS320 900 GeV <Nchg> = 14.2
pyP329 900 GeV <Nchg> = 14.7
The amount of activity in “min-bias” collisions (multiplicity distribution,
pT distribution, PTsum distribution, dNchg/dη
η).
Probability
0.06
0.04
0.02
PTmax Direction
0
5
10
Initial-State Radiation
“Toward”
“Transverse”
“Away”
The amount of activity in the “underlying event” in hard scattering
events (“transverse” Nchg distribution, “transverse” pT distribution,
“transverse” PTsum distribution for events with PTmax > 5 GeV/c).
"Transverse" Charged Density
Final-State
Ra diation
generator level
Initial-State Radiation
pyDW
pyS320
0.2
HC 900 GeV
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.0
0
2
4
6
8
10
12
14
16
18
20
PTmax (GeV/c)
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
“Toward”
1.2
Underlying Event
“Transverse”
“Transverse”
“Away”
We should map out the energy dependence of the “underlying
event” in a hard scattering process from 900 GeV to 14 TeV!
"Transverse" Charged Density
Proton
Final-State
Ra diation
40
∆φ
Outgoing Parton
Outgoing Parton
35
0.4
PT(hard)
Underlying Event
30
RDF Preliminary
PTmax Direction
Proton
25
0.6
Underlying Event
“Transverse”
Outgoing Parton
20
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
Proton
Underlying Event
15
Number of Charged Particles
PT(hard)
Proton
Charged Particles (|η
η|<2.0, all pT)
0.00
∆φ
Outgoing Parton
HC 900 GeV
Normalized to 1
RDF Preliminary
py Tune DW generator level
0.8
0.4
PTmax = 5.25 GeV/c
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.1
1.0
10.0
100.0
Center-of-Mass Energy (TeV)
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 25
Important 900 GeV Measurements
“Minumum Bias” Collisions
Proton
Charged Multiplicity Distribution
0.08
0.16
Proton
pyA <Nchg>
= 5.0 STdev = 4.5
RDF
Preliminary
RDF Preliminary
pyDW
900
GeV
<Nchg>==14.2
5.3
pyA
900
GeV
<Nchg>
pyS320
900GeV
GeV<Nchg>
<Nchg> = 5.2
pyDW
900
14.4
pyS320
GeV<Nchg>
<Nchg>= =5.314.2
pyP329 900
900 GeV
pyP329 900 GeV <Nchg> = 14.7
The amount of activity in “min-bias” collisions (multiplicity distribution,
pT distribution, PTsum distribution, dNchg/dη
η).
Probability
0.06
0.12
0.04
0.08
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.04
0.02
PTmax Direction
0
25
4
10
Initial-State Radiation
“Toward”
Outgoing Parton
Final-State
Ra diation
“Transverse”
“Away”
The amount of activity in the “underlying event” in hard scattering
events (“transverse” Nchg distribution, “transverse” pT distribution,
“transverse” PTsum distribution for events with PTmax > 5 GeV/c).
"Transverse"
Charged Density
Probability
Underlying Event
“Transverse”
RDF Preliminary
generator level
Initial-State Radiation
16
40
py64DW <Nchg> = 3.5 <NchgDen> = 0.42
pyS320 <Nchg> = 3.4 <NchgDen> = 0.41
pyDW
RDF Preliminary
generator level
pyS320
0.2
0.06
HC 900 GeV PTmax > 5 GeV/c
HC 900 GeV
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.0
0.00
00
12
2 4 3
64
58
6
107
812
9 1410
16
11
1218 13
20
14
PTmax
(GeV/c)Particles
Number
of Charged
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
“Toward”
1.2
Underlying Event
“Transverse”
“Transverse”
“Away”
We should map out the energy dependence of the “underlying
event” in a hard scattering process from 900 GeV to 14 TeV!
"Transverse" Charged Density
Proton
Final-State
Ra diation
14
35
∆φ
Outgoing Parton
Outgoing Parton
12
30
0.4
0.12
PT(hard)
Underlying Event
10
25
0.6
0.18
PTmax Direction
Proton
8
20
"Transverse"
Charged
Particle
Density:
dN/dη
ηdφ
φ
"Transverse"
Charged
Particle
Multiplicity
Proton
Underlying Event
6
15
Number of Charged Particles
PT(hard)
Proton
Charged Particles (|η
η|<2.0, all pT)
0.00
∆φ
Outgoing Parton
HC HC
900900
GeVGeV
Normalized to 1
Normalized to 1
RDF Preliminary
py Tune DW generator level
0.8
0.4
PTmax = 5.25 GeV/c
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.1
1.0
10.0
100.0
Center-of-Mass Energy (TeV)
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 26
Important 900 GeV Measurements
“Minumum Bias” Collisions
Proton
Charged Multiplicity Distribution
0.08
0.16
Proton
pyA <Nchg>
= 5.0 STdev = 4.5
RDF
Preliminary
RDF Preliminary
pyDW
900
GeV
<Nchg>==14.2
5.3
pyA
900
GeV
<Nchg>
pyS320
900GeV
GeV<Nchg>
<Nchg> = 5.2
pyDW
900
14.4
pyS320
GeV<Nchg>
<Nchg>= =5.314.2
pyP329 900
900 GeV
pyP329 900 GeV <Nchg> = 14.7
The amount of activity in “min-bias” collisions (multiplicity distribution,
pT distribution, PTsum distribution, dNchg/dη
η).
Probability
0.06
0.12
0.04
0.08
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.04
0.02
Normalized to 1
Normalized to 1
PTmax Direction
0
25
4
10
Initial-State Radiation
“Toward”
Outgoing Parton
Final-State
Ra diation
“Transverse”
“Away”
The amount of activity in the “underlying event” in hard scattering
events (“transverse” Nchg distribution, “transverse” pT distribution,
“transverse” PTsum distribution for events with PTmax > 5 GeV/c).
"Transverse"
Charged Density
Probability
Underlying Event
“Transverse”
RDF Preliminary
generator level
Initial-State Radiation
16
40
py64DW <Nchg> = 3.5 <NchgDen> = 0.42
pyS320 <Nchg> = 3.4 <NchgDen> = 0.41
pyDW
RDF Preliminary
generator level
pyS320
0.2
0.06
We get 3 events
here!
HC 900 GeV PTmax > 5 GeV/c
HC 900 GeV
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.0
0.00
00
12
2 4 3
64
58
6
107
812
9 1410
16
11
1218 13
20
14
PTmax
(GeV/c)Particles
Number
of Charged
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
“Toward”
1.2
Underlying Event
“Transverse”
“Transverse”
“Away”
We should map out the energy dependence of the “underlying
event” in a hard scattering process from 900 GeV to 14 TeV!
"Transverse" Charged Density
Proton
Final-State
Ra diation
14
35
∆φ
Outgoing Parton
Outgoing Parton
12
30
0.4
0.12
PT(hard)
Underlying Event
T
10
25
0.6
0.18
PTmax Direction
Proton
8
20
"Transverse"
Charged
Particle
Density:
dN/dη
ηdφ
φ
"Transverse"
Charged
Particle
Multiplicity
Proton
Underlying Event
6
15
Number of Charged Particles
PT(hard)
Proton
η
0.00
∆φ
Outgoing Parton
For every 1,000
events
here
Charged Particles (|η
η|<2.0, all p )
HC HC
900900
GeVGeV
RDF Preliminary
py Tune DW generator level
0.8
0.4
PTmax = 5.25 GeV/c
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.1
1.0
10.0
100.0
Center-of-Mass Energy (TeV)
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 27
Important 900 GeV Measurements
“Minumum Bias” Collisions
Proton
Charged Multiplicity Distribution
0.08
0.16
Proton
pyA <Nchg>
= 5.0 STdev = 4.5
RDF
Preliminary
RDF Preliminary
pyDW
900
GeV
<Nchg>==14.2
5.3
pyA
900
GeV
<Nchg>
pyS320
900GeV
GeV<Nchg>
<Nchg> = 5.2
pyDW
900
14.4
pyS320
GeV<Nchg>
<Nchg>= =5.314.2
pyP329 900
900 GeV
pyP329 900 GeV <Nchg> = 14.7
The amount of activity in “min-bias” collisions (multiplicity distribution,
pT distribution, PTsum distribution, dNchg/dη
η).
Probability
0.06
0.12
0.04
0.08
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.04
0.02
Normalized to 1
Normalized to 1
PTmax Direction
0
∆φ
25
4
10
Initial-State Radiation
“Toward”
Outgoing Parton
Final-State
Ra diation
“Transverse”
“Away”
T
"Transverse"
Charged Density
Probability
Underlying Event
“Transverse”
RDF Preliminary
generator level
Initial-State Radiation
16
40
py64DW <Nchg> = 3.5 <NchgDen> = 0.42
pyS320 <Nchg> = 3.4 <NchgDen> = 0.41
pyDW
RDF Preliminary
generator level
pyS320
0.2
0.06
We get 3 events
here!
HC 900 GeV PTmax > 5 GeV/c
HC 900 GeV
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
Charged Particles (|η
η|<2.0, PT>0.5 GeV/c)
0.0
0.00
00
12
2 4 3
64
58
6
107
812
9 1410
16
11
1218 13
20
14
PTmax
(GeV/c)Particles
Number
of Charged
"Transverse" Charged Particle Density: dN/dη
ηdφ
φ
“Toward”
1.2
Underlying Event
“Transverse”
“Transverse”
“Away”
We should map out the energy dependence of the “underlying
event” in a hard scattering process from 900 GeV to 14 TeV!
"Transverse" Charged Density
Proton
Final-State
Ra diation
14
35
∆φ
Outgoing Parton
Outgoing Parton
12
30
0.4
0.12
PT(hard)
Underlying Event
T
10
25
0.6
0.18
PTmax Direction
Proton
8
20
"Transverse"
Charged
Particle
Density:
dN/dη
ηdφ
φ
"Transverse"
Charged
Particle
Multiplicity
Proton
Underlying Event
6
15
Number of Charged Particles
PT(hard)
Proton
η
0.00
It is very important to measure
BOTH “min-bias” and the and the
“underlying event” at 900 GeV!
To do this
we need to collect
The amount of activity in the “underlying
event” in hard scattering
events (“transverse” Nchg distribution,
“transverse”
p distribution,
about
5,000,000
CMS
“transverse” PTsum distribution for events with PTmax > 5 GeV/c).
min-bias triggers!
Outgoing Parton
For every 1,000
events
here
Charged Particles (|η
η|<2.0, all p )
HC HC
900900
GeVGeV
RDF Preliminary
py Tune DW generator level
0.8
0.4
PTmax = 5.25 GeV/c
Charged Particles (|η
η|<1.0, PT>0.5 GeV/c)
0.0
0.1
1.0
10.0
100.0
Center-of-Mass Energy (TeV)
CMS-QCD Group Meeting
November 10, 2009
Rick Field – Florida/CDF/CMS
Page 28