Physics in Collision
Min-Bias and the Underlying Event at the LHC
Rick Field
University of Florida
Outline
 How well did we do at predicting the behavior of the
“underlying event” at the LHC (900 GeV and 7 TeV)?
 How universal are the QCD Monte-Carlo model tunes?
 Examine the connection between the “underlying event”

in a hard scattering process (UE) and “min-bias”
collisions (MB).
How well can we predict “min-bias” collisions at the LHC?
CMS
Outgoing Parton
“Minimum Bias” Collisions
PT(hard)
 Strange particle and baryon production
Proton
Proton
at the LHC.
Kshort
K+
u s
d s +d s
K-
u s
PIC 2011, Vancouver
August 29, 2011
p
uud

ud s
 
dss
Initial-State Radiation
Proton
Proton
Underlying Event
Outgoing Parton
Underlying Event
ATLAS
Final-State
Radiation
UE&MB@CMS
Rick Field – Florida/CDF/CMS
Page 1
“Towards”, “Away”, “Transverse”
“Leading Jet”
Jet #1 Direction

“Toward”
“Transverse”
“Transverse”
“Away”
Charged
PTsum
Density
(GeV/c)
Average
Charged
Density
Charged PTsum
ParticleDensity:
Density:dPT/dhd
dN/dhd
Charged
5
100.0
CDFCDF
RunRun
2 Preliminary
2 Preliminary
4
data corrected
data corrected
pyA generator level
pyA generator level
10.0
3
"Toward"
"Away"
"Toward"
"Away"
Factor of ~16
"Transverse" "Leading Jet"
Factor of MidPoint
~4.5 R=0.7 |h(jet#1)|<2
2
1.0
"Transverse"
1
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
ChargedParticles
Particles(|h|<1.0,
(|h|<1.0,PT>0.5
PT>0.5GeV/c)
GeV/c)
Charged
0 0.1
0 0
50 50
100100
150
150
200
200
250
250
300
300
350
350
400
400
PT(jet#1)
PT(jet#1)(GeV/c)
(GeV/c)

charged
particles,
dN/dhd,
pT > 0.5with
GeV/c
< 1 for
 CDF
CDF data
data at
at 1.96
1.96 TeV
TeV on
on the
the density
chargedofparticle
scalar
pT sum
density,with
dPT/dhd,
pT >and
0.5|h|
GeV/c
and
“leading
eventsjet”
as aevents
function
the leading
jetleading
pT for the
“away”, and
“transverse”
|h| < 1 forjet”
“leading
as aoffunction
of the
jet “toward”,
pT for the “toward”,
“away”,
and
regions.
The
data
are
corrected
to
the
particle
level
(with
errors
that
include
both
the
statistical
“transverse” regions. The data are corrected to the particle level (with errors that include both error
the and
the
systematic
and areuncertainty)
compared with
Tune with
A at PYTHIA
the particle
level
generator
statistical
erroruncertainty)
and the systematic
and PYTHIA
are compared
Tune
A (i.e.
at the
particle
level).
level (i.e. generator level).
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 2
Charged Particle Density
Charged
Particle
Density:
dN/dhd
"Away"
Charged
Particle
Density:
dN/dhd
"Transverse"
Charged
Density:
dN/dhd
Charged
ParticleParticle
Density:
dN/dhd
34
CDFRun
Run2 2Preliminary
Preliminary
CDF
data
corrected
data
corrected
generator
levellevel
theory
pyA
generator
0.9
3
Average
ChargedDensity
Density
"Away" Charged
"Transverse"
ChargedDensity
Density
Average Charged
1.2
4
"Leading
Jet"
"Away"
"Toward"
2
0.6
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
"Z-Boson"
1
0.3
"Transverse"
CDF Run 2 Preliminary
"Leading Jet"
data
data corrected
corrected
generator
level theory
pyAW generator
level
3
2
"Away"
"Drell-Yan Production"
70 < M(pair) < 110 GeV
2
1
1
"Transverse"
"Z-Boson"
Charged
Charged Particles
Particles(|h|<1.0,
(|h|<1.0,PT>0.5
PT>0.5GeV/c)
GeV/c)
"Toward"
00
0
0.0
00
20
20
40
40
60
60
80
80
100
100
120
120
140
140
160
160
180
180
00
200
200
20
60
Jet #1 Direction
Z-Boson Direction

Outgoing Parton
“Transverse”
Underlying Event
“Away”
140
160
80
180
200
100
Outgoing Parton
“Toward”
Proton
AntiProton
Underlying Event
120
60
Initial-State Radiation
Initial-State Radiation
Proton
“Transverse”
100
High PT Z-Boson Production
PT(hard)
“Toward”
80
40
PT(jet#1)
or PT(Z-Boson)
(GeV/c)
PT(Z-Boson)
(GeV/c)
PT(jet#1)
(GeV/c) (GeV/c)
PT(jet#1)
or PT(Z-Boson)

40
20
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
Charged
Particles
(|h|<1.0,
PT>0.5
GeV/c)
excluding the lepton-pair
“Transverse”
AntiProton
“Transverse”
“Away”
Outgoing Parton
Final-State
Radiation
Z-boson
 CDF data at 1.96 TeV on the density of charged particles, dN/dhd, with pT > 0.5 GeV/c and |h| < 1 for “Z-
Boson” and “Leading Jet” events as a function of the leading jet pT or PT(Z) for the “toward”, “away”, and
“transverse” regions. The data are corrected to the particle level and are compared with PYTHIA Tune AW
and Tune A, respectively, at the particle level (i.e. generator level).
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 3
Charged Particle Density
1.96 TeV
data corrected
pyDW generator level
Charged Particle Density
Average Charged Density
3
Drell-Yan Production
70 < M(pair) < 110 GeV
2
1
Average Charged Density
Large increase in the UE
in going from 1.96 TeV
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
"Toward" Charged Particle Density: dN/dhd
to 7 TeV as predicted by
3
Tune DW! 1.2 RDF Preliminary
CDF RunPYTHIA
2
CMS Preliminary
data corrected
"Away"
pyDW generator level
0.8
Drell-Yan
Production
Charged Particles
(|h|<1.0, PT>0.5
GeV/c)
excluding the lepton-pair
0
10
20
30
40
50
60
0
70
PT(lepton-pair) GeV/c
80
20
90
Initial-State Radiation
“Transverse”
“Transverse”
“Away”
"Toward"
Charged Particles (PT>0.5 GeV/c)
0 60
PT(lepton-pair) GeV/c
Outgoing Parton
T
"Transverse"
1
100
40
High P Z-Boson Production
CDF:Proton-Antiproton
Collisions at 1.96 GeV
Lepton Cuts: pT > 20 GeV |h| < 1.0
“Toward”
Proton
Mass Cut:
70 < M(lepton-pair) < 110
GeV
AntiProton
Charged Particles: pT > 0.5 GeV/c |h| < 1.0
Z-Boson Direction
"Away"
Drell-Yan Production
60 < M(pair) < 120 GeV
2
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
excluding the lepton-pair
0
0.0
0
CMS
CDF 1.96 TeV
0.4
"Transverse"
"Toward"
7 TeV
data corrected
CMS pyDW
7 TeV
generator level
2080
40
100
60
80
100
PT(lepton-pair) GeV/c
High P Z-Boson Production
CMS: Proton-Proton
Collisions at 7 GeV

Lepton Cuts: pT > 20 GeV |h| < 2.4
“Toward”
Mass Cut:Proton
60 < M(lepton-pair) < 120 Proton
GeV
Charged Particles: pT > 0.5 GeV/c |h| < 2.0
Z-Boson Direction
Outgoing Parton
T
Initial-State Radiation
“Transverse”
“Transverse”
“Away”
Z-boson
Z-boson
 CDF data at 1.96 TeV on the density of charged particles, dN/dhd, with pT > 0.5 GeV/c and |h| < 1 for
Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared
with PYTHIA Tune DW.
 CMS data at 7 TeV on the density of charged particles, dN/dhd, with pT > 0.5 GeV/c and |h| < 2 for DrellYan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with
PYTHIA Tune DW.
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 4
Charged PTsum Density
Charged
PTsum
Density:
dPT/dhd
"Away"
Charged
PTsum
Density:
dPT/dhd
20
10.0
2.0
100.0
CDF
Run
2 Preliminary
CDF
Run
2 Preliminary
corrected
datadata
corrected
pyA generator
level
generator
level theory
1.5
10.0
"Leading Jet"
"Toward"
"Away"
1.0
"Transverse"
1.0
"Leading Jet"
MidPoint R=0.7 |h(jet#1)|<2
0.5
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
Charged Particles (|h|<1.0, PT>0.5 GeV/c)
"Z-Boson"
0.00.1
0 0
2020
4040
6060
8080
100
100
120
120
140
140
160
160
180
180
200
200
Charged
Density(GeV/c)
(GeV/c)
"Away" PTsum
PTsum Density
Charged PTsum
Density
"Transverse"
PTsum
Density(GeV/c)
(GeV/c)
"Transverse"
Charged
Density:
dPT/dhd
Charged
PTsum PTsum
Density:
dPT/dhd
CDF
Run
Preliminary
CDF
Run
22
Preliminary
15
"Toward"
5
"Drell-Yan Production"
70 < M(pair) < 110 GeV
0
0.1
00
20
40
20
60
Outgoing Parton
Z-Boson Direction

Underlying Event
“Away”
120
60
140
160
80
180
200
100
Outgoing Parton
“Toward”
AntiProton
Underlying Event
100
Initial-State Radiation
Initial-State Radiation
Proton
“Transverse”
80
40
High PT Z-Boson Production
PT(hard)
“Transverse”
Charged
ChargedParticles
Particles(|h|<1.0,
(|h|<1.0,PT>0.5
PT>0.5GeV/c)
GeV/c)
excluding the lepton-pair
PT(jet#1)
or PT(Z-Boson)
(GeV/c)
PT(Z-Boson)
(GeV/c)
Jet #1 Direction
“Toward”
"Transverse"
"Z-Boson"
10
1.0
(GeV/c)(GeV/c)
PT(jet#1)PT(jet#1)
or PT(Z-Boson)

"Away"
"Leading Jet"
data
corrected
data
corrected
pyAW generator
level
generator
level theory
Proton
“Transverse”
AntiProton
“Transverse”
“Away”
Outgoing Parton
Final-State
Radiation
Z-boson
 CDF data at 1.96 TeV on the charged scalar PTsum density, dPT/dhd, with pT > 0.5 GeV/c and |h| < 1 for “ZBoson” and “Leading Jet” events as a function of the leading jet pT or PT(Z) for the “toward”, “away”, and
“transverse” regions. The data are corrected to the particle level and are compared with PYTHIA Tune AW
and Tune A, respectively, at the particle level (i.e. generator level).
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 5
Charged PTsum Density
data corrected
pyDW generator level
data corrected
pyDW generator level
"Toward"
Drell-Yan Production
70 < M(pair) < 110 GeV
1.0
CDF 1.96 TeV
0.5
Charged Particles
(|h|<1.0,
PT>0.5 GeV/c)
Drell-Yan
Production
excluding the lepton-pair
0.1
20
40
60
0
80
20
PT(lepton-pair) GeV/c
Z-Boson Direction

"Transverse"
1.0
"Toward"
CMS
Drell-Yan Production
Charged Particles (PT>0.5 GeV/c)
60 < M(pair) < 120 GeV
High PT Z-Boson Production
0
60
100
40
20
80
40
100
Z-Boson Direction
Outgoing Parton

60
80
100
PT(lepton-pair) GeV/c
PT(lepton-pair) GeV/c
High PT Z-Boson Production
Initial-State Radiation
Outgoing Parton
Initial-State Radiation
“Toward”
“Toward”
Proton
“Transverse”
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
excluding the lepton-pair
0.1
0.0
0
data corrected
pyDW generator level
CMS 7 TeV
"Transverse"
1.0
Charged PTsum Density (GeV/c)
Charged PTsum Density (GeV/c)
10.0
Charged PTsum Density (GeV/c)
Large increase in the UE
inCharged
going from
1.96Density:
TeV dPT/dhd
Charged PTsum Density: dPT/dhd
PTsum
"Toward" Charged PTsum Density: dPT/dhd
to 7 TeV as predicted by
10.0
1.5
CMS Preliminary
CDF Run
2
1.96
TeV DW! "Away"
7 TeV
RDF Preliminary
PYTHIA
Tune
"Away"
Proton
AntiProton
“Transverse”
“Transverse”
“Away”
Proton
“Transverse”
“Away”
Z-boson
Z-boson
 CDF data at 1.96 TeV on the charged PTsum density, dPT/dhd, with pT > 0.5 GeV/c and |h| < 1 for Drell-
Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with
PYTHIA Tune DW.
 CMS data at 7 TeV on the charged PTsum density, dPT/dhd, with pT > 0.5 GeV/c and |h| < 1 for Drell-Yan
production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with
PYTHIA Tune DW.
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 6
PYTHIA Tune DW
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
Charged Particle Density
CMS Preliminary
"Transverse" Charged Density
1.2
7 TeV
data uncorrected
pyDW + SIM
0.8
CMS
900 GeV
0.4
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.2
RDF Preliminary
7 TeV
ATLAS corrected data
Tune DW generator level
0.8
ATLAS
900 GeV
0.4
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
30
35
40
45
50
0
2
4
6
8
10
 CMS preliminary data at 900 GeV and 7 TeV 
on the “transverse” charged particle density,
dN/dhd, as defined by the leading charged
particle jet (chgjet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 2. The data are
uncorrected and compared with PYTHIA
Tune DW after detector simulation.
16
18
20
ATLAS preliminary data at 900 GeV and 7
TeV on the “transverse” charged particle
density, dN/dhd, as defined by the leading
charged particle (PTmax) for charged particles
with pT > 0.5 GeV/c and |h| < 2.5. The data are
corrected and compared with PYTHIA Tune
DW at the generator level.
PT(chgjet#1) Direction
PTmax Direction


“Toward”
“Toward”
“Transverse”
“Transverse”
“Away”
PIC 2011, Vancouver
August 29, 2011
14
PTmax (GeV/c)
PT(chgjet#1) GeV/c
“Transverse”
12
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 7
PYTHIA Tune DW
"Transverse" Charged PTsum Density: dPT/dhd
1.5
CMS Preliminary
1.2
RDF Preliminary
7 TeV
data uncorrected
pyDW + SIM
CMS
0.8
PTsum Density (GeV/c)
Charged PTsum Density (GeV/c)
"Transverse" Charged PTsum Density: dPT/dhd
1.6
7 TeV
ATLAS corrected data
Tune DW generator level
1.0
900 GeV
ATLAS
Overall PYTHIA Tune DW
is in amazingly good agreement with the Charged Particles (|h|<2.5, PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
Tevatron Jet production 0.0
and
Drell-Yan
data
0
2
4
6
8
10
12
14
16
18
20
0
5
10
15
20
25
30
35
40
45
50
and
did
a
very
good
job
in
predicting
the
PTmax
(GeV/c)
PT(chgjet#1) (GeV/c)
LHC Jet production and Drell-Yan data!
 ATLAS preliminary data at 900 GeV and
 CMS preliminary data at 900 GeV and 7
(although
not
perfect)
7 TeV on the “transverse” charged PTsum
TeV on the “transverse” charged PTsum
900 GeV
0.4
density, dPT/dhd, as defined by the leading
charged particle jet (chgjet#1) for charged
particles with pT > 0.5 GeV/c and |h| < 2.
The data are uncorrected and compared
with PYTHIA Tune DW after detector
PT(chgjet#1) Direction
simulation.

0.5
density, dPT/dhd, as defined by the
leading charged particle (PTmax) for
charged particles with pT > 0.5 GeV/c and
|h| < 2.5. The data are corrected and
compared with PYTHIA Tune DW at the
generator level. PTmax Direction
“Toward”
“Transverse”
“Toward”
“Transverse”
“Transverse”
“Away”
PIC 2011, Vancouver
August 29, 2011
“Transverse”
“Away”
Rick Field – Florida/CDF/CMS
Page 8
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!
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
PARP(90)
PARP(82)
Color
Connections
Diffraction
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Outgoing Parton
Underlying Event
Final-State
Radiation
UE&MB@CMS
Page 9
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
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 10
CMS UE Data
"Transverse" Charged PTsum Density: dPT/dhd
"Transverse" Charged Particle Density: dN/dhd
2.0
CMS Preliminary
CMS Preliminary
data corrected
Tune Z1 generator level
7 TeV
PTsum Density (GeV/c)
Charged Particle Density
1.6
1.2
0.8
900 GeV
CMS
0.4
Tune Z1
data corrected
Tune Z1 generator level
1.6
7 TeV
1.2
CMS
0.8
900 GeV
Tune Z1
0.4
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0.0
0
10
20
30
40
50
60
70
80
90
100
0
10
PT(chgjet#1) GeV/c
PIC 2011, Vancouver
August 29, 2011
30
40
50
60
70
80
90
100
PT(chgjet#1) GeV/c
 CMS preliminary data at 900 GeV and 7
TeV on the “transverse” charged particle
density, dN/dhd, as defined by the leading
charged particle jet (chgjet#1) for charged
particles with pT > 0.5 GeV/c and |h| < 2.0.
The data are corrected and compared with
PYTHIA Tune Z1 at the generator level.
CMS corrected
data!
20
 CMS preliminary data at 900 GeV and 7
TeV on the “transverse” charged PTsum
density, dPT/dhd, as defined by the leading
charged particle jet (chgjet#1) for charged
particles with pT > 0.5 GeV/c and |h| < 2.0.
The data are corrected and compared with
PYTHIA Tune Z1 at the generator level.
Very nice agreement!
Rick Field – Florida/CDF/CMS
CMS corrected
data!
Page 11
ATLAS UE Data
"Transverse" Charged PTsum Density: dPT/dhd
"Transverse" Charged Particle Density: dN/dhd
1.5
RDF Preliminary
RDF Preliminary
7 TeV
ATLAS corrected data
Tune Z1 generator level
PTsum Density (GeV/c)
"Transverse" Charged Density
1.2
0.8
ATLAS
900 GeV
0.4
Tune Z1
7 TeV
ATLAS corrected data
Tune Z1 generator level
1.0
ATLAS
900 GeV
0.5
Tune Z1
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
Charged Particles (|h|<2.5, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
0
5
10
15
20
25
PTmax (GeV/c)
PTmax (GeV/c)
 ATLAS published data at 900 GeV and 7
TeV on the “transverse” charged particle
density, dN/dhd, as defined by the leading
charged particle (PTmax) for charged
particles with pT > 0.5 GeV/c and |h| < 2.5.
The data are corrected and compared with
PYTHIA Tune Z1 at the generator level.
 ATLAS published data at 900 GeV and 7
TeV on the “transverse” charged PTsum
density, dPT/dhd, as defined by the leading
charged particle (PTmax) for charged
particles with pT > 0.5 GeV/c and |h| < 2.5.
The data are corrected and compared with
PYTHIA Tune Z1 at the generrator level.
ATLAS publication – arXiv:1012.0791
December 3, 2010
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 12
CMS-ATLAS UE Data
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
1.6
RDF Preliminary
RDF Preliminary
CMS: Chgjet#1
data corrected
Tune Z1 generator level
Charged Particle Density
Charged Particle Density
1.6
1.2
0.8
CMS (red)
ATLAS (blue)
ATLAS: PTmax
0.4
Tune Z1
data corrected
Tune Z1 generator level
1.2
0.8
CMS (red)
ATLAS (blue)
Tune Z1
0.4
Charged Particles (PT > 0.5 GeV/c)
7 TeV
Charged Particles (PT > 0.5 GeV/c)
7 TeV
0.0
0.0
0
5
10
15
20
25
30
0
10
20
30
40
50
60
70
80
90
100
PTmax or PT(chgjet#1) (GeV/c)
PTmax or PT(chgjet#1) (GeV/c)
 CMS preliminary data at 7 TeV on the “transverse” charged particle density, dN/dhd, as
defined by the leading charged particle jet (chgjet#1) for charged particles with pT > 0.5 GeV/c
and |h| < 2.0 together with the ATLAS published data at 7 TeV on the “transverse” charged
particle density, dN/dhd, 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.
Amazing agreement!
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 13
ALICE UE Data
"Transverse" Charged PTsum Density: dPT/dhd
"Transverse" Charged Particle Density: dN/dhd
1.5
RDF Preliminary
RDF Preliminary
7 TeV
ALICE corrected data
Tune Z1 generator level
PTsum Density (GeV/c)
"Transverse" Charged Density
1.2
0.8
900 GeV
0.4
ALICE
Tune Z1
7 TeV
ALICE corrected data
Tune Z1 generator level
1.0
900 GeV
0.5
ALICE
Tune Z1
Charged Particles (|h|<0.8, PT>0.5 GeV/c)
Charged Particles (|h|<0.8, PT>0.5 GeV/c)
0.0
0.0
0
5
10
15
20
25
0
5
 ALICE preliminary data at 900 GeV and 7
TeV on the “transverse” charged particle
density, dN/dhd, as defined by the leading
charged particle (PTmax) for charged
particles with pT > 0.5 GeV/c and |h| < 0.8.
The data are corrected and compared with
PYTHIA Tune Z1 at the generator level.
PIC 2011, Vancouver
August 29, 2011
15
20
25
PTmax (GeV/c)
PTmax (GeV/c)
I read the points off
with a ruler!
10
 ALICE preliminary data at 900 GeV and 7
TeV on the “transverse” charged PTsum
density, dPT/dhd, as defined by the leading
charged particle (PTmax) for charged
particles with pT > 0.5 GeV/c and |h| < 0.8.
The data are corrected and compared with
PYTHIA Tune Z1 at the generrator level.
ALICE UE Data: Talk by S. Vallero
MPI@LHC 2010 Glasgow, Scotland
November 30, 2010
Rick Field – Florida/CDF/CMS
Page 14
PYTHIA Tune Z1
"Transverse"Charged
ChargedParticle
ParticleDensity:
Density:dN/dhd
dN/dhd
"Transverse"
1.2
"Transverse" Charged Particle Density: dN/dhd
1.5
CMSPreliminary
Preliminary
RDF
RDF Preliminary
data
corrected
data
corrected
Tune generator
Z1 generator
level
pyZ1
level
CMS 7 TeV7 TeV
Charged Particle Density
Charged
Charged Particle
Particle Density
Density
1.6
1.5
1.0
CDF 1.96 TeV
0.8
900 GeV
0.5
0.4
CMS 900 GeV
Tune Z1
data corrected
pyZ1 generator level
CMS 7 TeV
1.0
CDF 1.96 TeV
0.5
CMS 900 GeV
Tune Z1
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
Charged Particles (PT>0.5 GeV/c)
0.0
00
10
20
20
30
40
40
50
60
60
70
80
80
90
100
100
0
50
PT(chgjet#1)
GeV/c
PT(chgjet#1
or jet#1)
GeV/c
100
150
200
250
300
PT(chgjet#1 or jet#1) GeV/c
 CMS data at 900 GeV on the “transverse”
 CDF data at 1.96 TeV on the “transverse”
charged particle density, dN/dhd, as
charged particle density, dN/dhd, as
defined by the leading charged particle jet
defined by the leading calorimeter jet (jet#1)
(chgjet#1) for charged particles with pT >
for charged particles with pT > 0.5 GeV/c
0.5 GeV/c and |h| < 2.0. The data are
and |h| < 1.0. The data are corrected and
corrected and compared with PYTHIA Tune
compared with PYTHIA Tune Z1 at the
Z1 at the generator level.
generator level.
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 15
PYTHIA Tune Z1
"Transverse" Charged PTsum Density: dPT/dhd
"Transverse" Charged PTsum Density: dPT/dhd
2.0
2.0
RDF Preliminary
datacorrected
corrected
data
Tune
generator
level
pyZ1 Z1
generator
level
1.6
7 TeV
CMS
7 TeV
1.2
PTsum Density (GeV/c)
PTsum Density (GeV/c)
CMSPreliminary
Preliminary
RDF
CDF 1.96 TeV
0.8
900 GeV
CMS 900 GeV
Tune Z1
0.4
CMS 7 TeV
data corrected
pyZ1 generator level
1.6
CDF 1.96 TeV
1.2
0.8
Tune Z1
CMS 900 GeV
0.4
Charged Particles (PT>0.5 GeV/c)
Charged Particles (PT>0.5 GeV/c)
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
0.0
0.0
0
10
20
30
40
50
60
70
80
90
100
0
100
150
200
250
300
PT(chgjet#1 or jet#1) GeV/c
PT(chgjet#1
or jet#1)
GeV/c
PT(chgjet#1)
GeV/c
 CMS data at 900 GeV and 7 TeV on the
“transverse” charged PTsum density,
dPT/dhd, as defined by the leading charged
particle jet (chgjet#1) for charged particles
with pT > 0.5 GeV/c and |h| < 2.0. The data
are corrected and compared with PYTHIA
Tune Z1 at the generator level.
PIC 2011, Vancouver
August 29, 2011
50
 CDF data at 1.96 TeV on the “transverse”
charged PTsum density, dPT/dhd, 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 Z1 at the
generator level.
Rick Field – Florida/CDF/CMS
Page 16
PYTHIA Tune Z1
Tune Z1 describes the
energy dependence
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dhd
"Toward" Charged Particle Density: dN/dhd
fairly well!
3
1.2
Drell-Yan Production
70 < M(pair) < 110 GeV
2
1
CMS Preliminary
RDF Preliminary
1.96 TeV
data corrected
pyZ1 generator level
Charged Particle Density
Average Charged Density
CDF Run 2
Average Charged Density
3
data corrected
"Away"
pyZ1 generator level
0.8
Charged Particles
(|h|<1.0, Production
PT>0.5 GeV/c)
Drell-Yan
excluding the lepton-pair
0
10
20
30
40
50
60
0
70
80
20
PT(lepton-pair) GeV/c
Z-Boson Direction

High PT Z-Boson Production
90
"Transverse"
1
"Toward"
0
100
40
0 60
2080
40
100
Z-Boson Direction

High PT Z-Boson Production
Initial-State Radiation
80
100
Outgoing Parton
Initial-State Radiation
“Toward”
“Toward”
Proton
“Transverse”
60
PT(lepton-pair) GeV/c
PT(lepton-pair) GeV/c
Outgoing Parton
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
excluding the lepton-pair
Charged Particles (PT>0.5 GeV/c)
0.0
0
"Away"
Drell-Yan Production
60 < M(pair) < 120 GeV
2
CDF 1.96 TeV
0.4
"Transverse"
"Toward"
CMS
7 TeV
data corrected
pyZ1
generator level
CMS 7
TeV
Proton
AntiProton
“Transverse”
“Transverse”
“Away”
Proton
“Transverse”
“Away”
Z-boson
Z-boson
 CDF data at 1.96 TeV on the density of charged particles, dN/dhd, with pT > 0.5 GeV/c and |h| < 1 for
Drell-Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared
with PYTHIA Tune Z1.
 CMS data at 7 TeV on the density of charged particles, dN/dhd, with pT > 0.5 GeV/c and |h| < 2 for DrellYan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with
PYTHIA Tune Z1.
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 17
PYTHIA Tune Z1
Charged PTsum Density: dPT/dhd
Charged PTsum Density: dPT/dhd
"Toward" Charged PTsum Density: dPT/dhd
10.0
1.5
1.96 TeV
data corrected
pyZ1 generator level
"Away"
RDF
Preliminary
data corrected
pyZ1 generator level
"Toward"
Drell-Yan Production
70 < M(pair) < 110 GeV
1.0
CDF 1.96 TeV
0.5
Charged Particles
(|h|<1.0,
PT>0.5 GeV/c)
Drell-Yan
Production
excluding the lepton-pair
0.1
20
40
60
0
80
20
PT(lepton-pair) GeV/c
Z-Boson Direction

7 TeV
"Transverse"
1.0
"Toward"
Drell-Yan Production
Charged Particles (PT>0.5 GeV/c)
60 < M(pair) < 120 GeV
High PT Z-Boson Production
100
40
0
60
20
80
CMS
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
excluding the lepton-pair
40
100
Z-Boson Direction
Outgoing Parton

60
80
100
PT(lepton-pair) GeV/c
PT(lepton-pair) GeV/c
High PT Z-Boson Production
Initial-State Radiation
Outgoing Parton
Initial-State Radiation
“Toward”
“Toward”
Proton
“Transverse”
"Away"
data corrected
pyZ1 generator level
0.1
0.0
0
CMS Preliminary
CMS 7 TeV
"Transverse"
1.0
Charged PTsum Density (GeV/c)
CDF Run 2
Charged PTsum Density (GeV/c)
Charged PTsum Density (GeV/c)
10.0
Proton
AntiProton
“Transverse”
“Transverse”
“Away”
Proton
“Transverse”
“Away”
Z-boson
Z-boson
 CDF data at 1.96 TeV on the charged PTsum density, dPT/dhd, with pT > 0.5 GeV/c and |h| < 1 for Drell-
Yan production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with
PYTHIA Tune Z1.
 CMS data at 7 TeV on the charged PTsum density, dPT/dhd, with pT > 0.5 GeV/c and |h| < 2 for Drell-Yan
production as a function of PT(Z) for the “toward”, “away”, and “transverse” regions compared with
PYTHIA Tune Z1.
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 18
PYTHIA Tune Z1
"Transverse" Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
1.2
1.5
RDF Preliminary
data corrected
pyZ1 generator level
Charged Particle Density
Charged Particle Density
RDF Preliminary
CMS 7 TeV
1.0
CDF 1.96 TeV
0.5
CMS 900 GeV
Tune Z1
0.8
CDF 1.96 TeV
0.4
Tune Z1
0.0
0
20
40
60
80
100
0
20
PT(chgjet#1 or jet#1) GeV/c
3.0
7 TeV
1.2
0.8
Drell-Yan Production
0.4
80
100
RDF Preliminary
Chgjet Production
Charged Particle Density
data corrected
pyZ1 generator level
60
"Away" Charged Particle Density: dN/dhd
1.6
CMS Preliminary
40
PT(lepton-pair) GeV/c
"Transverse" Charged Particle Density: dN/dhd
Charged Particle Density
Charged Particles (PT>0.5 GeV/c)
Drell-Yan Production
Charged Particles (PT>0.5 GeV/c)
0.0
CMS 7 TeV
data corrected
pyZ1 generator level
Tune Z1
data corrected
pyZ1 generator level
CDF 1.96 TeV
2.0
CMS 7 TeV
1.0
Tune Z1
Drell-Yan Production
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
0
10
20
30
40
50
60
70
80
90
100
0
40
60
80
100
PT(lepton-pair) GeV/c
PT(chgjet#1) or PT(lepton-pair) GeV/c
PIC 2011, Vancouver
August 29, 2011
20
Rick Field – Florida/CDF/CMS
Page 19
PYTHIA Tune Z1
"Transverse" Charged PTsum Density: dPT/dhd
"Transverse" Charged PTsum Density: dPT/dhd
2.0
Charged PTsum Density (GeV/c)
2.0
PTsum Density (GeV/c)
RDF Preliminary
data corrected
pyZ1 generator level
1.6
CMS 7 TeV
1.2
CDF 1.96 TeV
0.8
CMS 900 GeV
0.4
Tune Z1
Charged PTsum Density (GeV/c)
2.0
1.5
CMS 7 TeV
1.0
CDF 1.96 TeV
0.5
Charged Particles (PT>0.5 GeV/c)
90
100
10.0
CMS Preliminary
7 TeV
data corrected
pyZ1 generator level
RDF Preliminary
What about Min-Bias?
Chgjet Production
Charged PTsum Density (GeV/c)
0
Tune Z1
data corrected
pyZ1 generator level
Drell-Yan Production
Overall amazingly good agreement
0.0
with
0
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80the90LHC
100 and Tevatron
PT(chgjet#1 or jet#1) GeV/c
Jet production and Drell-Yan! PT(lepton-pair) GeV/c
not perfect yet)
"Away" Charged PTsum Density: dPT/dhd
"Transverse" Charged PTsum Density:(although
dPT/dhd
Charged Particles (PT>0.5 GeV/c)
0.0
RDF Preliminary
1.5
1.0
Tune Z1
0.5
Drell-Yan Production
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
data corrected
pyZ1 generator level
8.0
CDF 1.96 TeV
Drell-Yan Production
6.0
CMS 7 TeV
4.0
Tune Z1
2.0
Charged Particles (PT>0.5 GeV/c)
0.0
0.0
0
10
20
30
40
50
60
70
80
90
100
0
10
30
40
50
60
70
80
90
PT(lepton-pair) GeV/c
PT(chgjet#1) or PT(lepton-pair) GeV/c
PIC 2011, Vancouver
August 29, 2011
20
Rick Field – Florida/CDF/CMS
Page 20
100
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
+…
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 21
The “Underlying Event”
Select inelastic non-diffractive events
that contain a hard scattering
Proton
Hard parton-parton
collisions is hard
(pT > ≈2 GeV/c)
Proton
1/(pT)4→ 1/(pT2+pT02)2
The “underlying-event” (UE)!
Proton
Given that you have one hard
scattering it is more probable to
have MPI! Hence, the UE has
more activity than “min-bias”.
PIC 2011, Vancouver
August 29, 2011
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 22
Allow leading hard
scattering to go to
zero pT with same
cut-off as the MPI!
Model of sND
Proton
Proton
Proton
Proton
Proton
+
Proton
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
1/(pT)4→ 1/(pT2+pT02)2
Model of the inelastic nondiffractive cross section!
+
Proton
Proton
Proton
+
Proton
Proton
+…
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 23
UE Tunes
Allow primary hard-scattering to
go to pT = 0 with same cut-off!
“Underlying Event”
Fit the “underlying
event” in a hard
scattering process.
Proton
Proton
1/(pT)4→ 1/(pT2+pT02)2
“Min-Bias”
“Min-Bias” (add
(ND)single & double diffraction)
Proton
Predict MB (ND)!
Proton
+
+
Proton
Proton
Proton
Single Diffraction
Predict MB (IN)!
PIC 2011, Vancouver
August 29, 2011
+…
Proton
+
Proton
Proton
Double Diffraction
M2
M
Rick Field – Florida/CDF/CMS
M1
Page 24
Min-Bias Collisions
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
6
CMS Data
ALICE Data
PYTHIA Tune Z1
PYTHIA Tune Z1
Charged Particle Density
Charged Particle Density
8
6
NSD = ND + DD
4
Tune Z1
CMS
2
pyZ1 ND = dashed
pyZ1 NSD = solid
7 TeV
NSD (all pT)
4
2
Tune Z1
INEL (all pT)
0
ALICE
INEL = NSD + SD
pyZ1 NSD = dashed
pyZ1 INEL = solid
900 GeV
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
Pseudo-Rapidity h
-2
-1
0
1
2
3
Pseudo-Rapidity h
 CMS NSD data on the charged particle
rapidity distribution at 7 TeV compared
with PYTHIA Tune Z1. The plot shows
the average number of particles per NSD
collision per unit h, (1/NNSD) dN/dh.
 ALICE NSD data on the charged particle
rapidity distribution at 900 GeV compared
with PYTHIA Tune Z1. The plot shows
the average number of particles per INEL
collision per unit h, (1/NINEL) dN/dh.
“Minimum Bias” Collisions
Okay not perfect, but remember
Proton
we know that SD and DD are not modeled well!
Proton
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 25
4
MB versus UE
Divide be 2p
Charged Particle Density: dN/dhd
Charged Particle Density: dN/dh
2.5
CMS Data
CMS Data
PYTHIA Tune Z1
PYTHIA Tune Z1
Charged Particle Density
Charged Particle Density
8
6
NSD = ND + DD
4
Tune Z1
CMS
2
pyZ1 ND = dashed
pyZ1 NSD = solid
7 TeV
NSD (all pT)
2.0
1.5
1.0
0.5
pyZ1 ND = dashed
7 TeV
NSD (all pT)
pyZ1 NSD = solid
0.0
0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-2
-1
0
1
2
3
4
Pseudo-Rapidity h
Pseudo-Rapidity h
 CMS NSD data on the charged particle
 CMS NSD data on the charged particle rapidity
rapidity distribution at 7 TeV compared
distribution at 7 TeV compared with PYTHIA
with PYTHIA Tune Z1. The plot shows
Tune Z1. The plot shows the average number of
the average number of charged particles
charged particles per NSD collision per unit h,
per NSD collision per unit h, (1/NNSD)
(1/NNSD) dN/dhd.
dN/dh.
“Minimum Bias” Collisions
Proton
PIC 2011, Vancouver
August 29, 2011
Proton
Rick Field – Florida/CDF/CMS
Page 26
MB versus UE
Charged Particle Density: dN/dhd
Transverse Charged Particle Density: dN/dhd
2.5
RDF Preliminary
CMS Data
PYTHIA Tune Z1
PYTHIA Tune Z1
Charged Particle Density
Charged Particle Density
2.5
2.0
Factor of 2!
1.5
1.0
Charged Particles (|h| < 2, all pT)
0.5
Tune Z1
CMS
2.0
Tune Z1
NSD = ND + DD
1.5
1.0
0.5
7 TeV ND
pyZ1 ND = dashed
7 TeV
NSD (all pT)
pyZ1 NSD = solid
0.0
0.0
0
5
10
15
20
25
-4
-3
-2
-1
0
1
2
3
Pseudo-Rapidity h
PT max (GeV/c)
 Shows the density of charged particles in
the “transverse” region as a function of
PTmax for charged particles (All pT, |h| <
2) at 7 TeV from PYTHIA Tune Z1.
Outgoing Parton
 CMS NSD data on the charged particle rapidity
distribution at 7 TeV compared with PYTHIA
Tune Z1. The plot shows the average number of
charged particles per NSD collision per unit h,
(1/NNSD) dN/dhd.
“Minimum Bias” Collisions
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Outgoing Parton
PIC 2011, Vancouver
August 29, 2011
4
Proton
Underlying Event
Proton
Final-State
Radiation
Rick Field – Florida/CDF/CMS
Page 27
MB versus UE
Charged Particle Density: dN/dhd
"Transverse" Charged Particle Density: dN/dhd
2.5
CMS Data
ATLAS
2.0
Charged Particle Density
"Transverse" Charged Density
2.5
Factor of 2!
1.5
RDF Preliminary
1.0
ATLAS corrected data
Tune Z1 generator level
0.5
7 TeV
Charged Particles (pT > 0.1 GeV/c, |h|<2.5)
CMS
PYTHIA Tune Z1
2.0
Tune Z1
1.0
0.5
pyZ1 ND = dashed
7 TeV
NSD (all pT)
0.0
NSD = ND + DD
1.5
pyZ1 NSD = solid
0.0
0
2
4
6
8
10
12
14
16
18
20
-4
-3
PTmax (GeV/c)
-2
-1
0
1
2
3
Pseudo-Rapidity h
 ATLAS data on the density of charged
particles in the “transverse” region as a
function of PTmax for charged particles
(pT > 0.1 GeV/c, |h| < 2.5) at 7 TeV
compared with PYTHIA Tune Z1.
Outgoing Parton
 CMS NSD data on the charged particle rapidity
distribution at 7 TeV compared with PYTHIA
Tune Z1. The plot shows the average number of
charged particles per NSD collision per unit h,
(1/NNSD) dN/dhd.
“Minimum Bias” Collisions
PT(hard)
Initial-State Radiation
Proton
Proton
Underlying Event
Outgoing Parton
PIC 2011, Vancouver
August 29, 2011
4
Proton
Underlying Event
Proton
Final-State
Radiation
Rick Field – Florida/CDF/CMS
Page 28
NSD Multiplicity Distribution
Charged Multiplicity Distribution
1.0E-01
RDF Preliminary
data CMS NSD
pyZ1 generator level
Difficult to produce
enough events with
large multiplicity!
CMS
Probability
1.0E-02
7 TeV
900 GeV
1.0E-03
Charged Particles
(all PT, |h|<2.0)
Tune Z1
1.0E-04
0
20
40
60
80
100
Number of Charged Particles
 Generator level charged multiplicity distribution (all pT, |h| < 2) at 900 GeV and 7
TeV. Shows the NSD = HC + DD prediction for Tune Z1. Also shows the CMS
NSD data.
“Minumum Bias” Collisions
Proton
PIC 2011, Vancouver
August 29, 2011
Okay not perfect!
But not that bad!
Rick Field – Florida/CDF/CMS
Proton
Page 29
MB & UE
"Transverse" Charged Particle Multiplicity
Charged Multiplicity Distribution
1.0E+00
1.0E-01
“Min-Bias”
RDF Preliminary
“Underlying Event”
data CMS NSD
pyZ1 generator level
Data Corrected
Tune Z1 generator level
1.0E-01
CMS
PT(chgjet#1) > 3 GeV/c
Probability
Probability
1.0E-02
7 TeV
900 GeV
1.0E-03
1.0E-02
900 GeV
1.0E-04
0
20
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
1.0E-05
100
 Generator level charged multiplicity
distribution (all pT, |h| < 2) at 900 GeV
and 7 TeV. Shows the NSD = HC + DD
prediction for Tune Z1. Also shows the
CMS NSD data.
PIC 2011, Vancouver
August 29, 2011
CMS
Tune Z1
Tune Z1
Difficult to produce
40
60
80
enough
events
with
Number of Charged Particles
large multiplicity!
7 TeV
1.0E-03
1.0E-04
Charged Particles
(all PT, |h|<2.0)
CMS Preliminary
0
5
10
15
20
25
30
35
Number of Charged Particles
Difficult to produce
 CMS corrected data at 900 GeV and 7 TeV
enough events with
on the charged particle multiplicity
large “transverse”
distribution in the “transverse” region for
multiplicity at low
charged particles (pT > 0.5 GeV/c, |h| < 2)
hard scale!
as defined by the leading charged particle
jet with PT(chgjet#1) > 3 GeV/c compared
with PYTHIA Tune Z1 at the generator
level.
Rick Field – Florida/CDF/CMS
Page 30
How Universal are the Tunes?
 Do we need a separate tune for each center-of-mass energy?
Outgoing Parton
PT(hard)
900 GeV, 1.96 TeV, 7 TeV, etc.
Initial-State Radiation
Proton
PYTHIA Tune DW did a nice (although not perfect)
job predicting the LHC Jet Production and Drell-Yan
UE data. I am still hoping for a single tune that will
describe all energies!
Proton
Underlying Event
Underlying Event
Outgoing Parton
Final-State
Radiation
Outgoing Parton
PT(hard)
Initial-State Radiation
Proton
 Do we need a separate tune for each hard QCD
Proton
Underlying Event
Underlying Event
subprocess? Jet Production, Drell-Yan Production, etc.
Outgoing Parton
The same tune can describe both Jet Production and Drell-Yan!
 Do we need separate tunes for “Min-Bias” (MB) and the
Proton
Final-State
Radiation
Color
“Minimum Bias” Collisions
Proton
Connections
“underlying event” (UE) in a hard scattering process?
PHTHIA Tune Z1 does fairly well at both the UE and MB,
but you cannot expect such a naïve approach to be perfect!
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Diffraction
Page 31
Kaon Production
Kshort Rapidity Distribution: dN/dY
Kshort Rapidity Distribution: dN/dY
0.5
0.4
CMS
CMS Data
PYTHIA Tune Z1
0.4
CMS & ALICE Data
INEL = NSD + SD
PYTHIA Tune Z1
7 TeV
0.3
dN/dY
dN/dY
CMS NSD
0.3
0.2
900 GeV
900 GeV
0.2
0.1
0.1
ALICE INEL
Tune Z1
NSD (all pT)
0.0
pyZ1 NSD = solid
Tune Z1
pyZ1 INEL = dashed
0.0
-4
-3
-2
-1
0
1
2
3
4
-4
-3
Rapidity Y
-2
-1
0
1
2
3
Rapidity Y

 CMS NSD data on the Kshort rapidity
distribution at 7 TeV and 900 GeV compared
with PYTHIA Tune Z1. The plot shows the
average number of Kshort per NSD collision per
unit Y, (1/NNSD) dN/dY.
CMS NSD data on the Kshort rapidity
distribution at 900 GeV and the ALICE point at
Y = 0 (INEL) compared with PYTHIA Tune Z1.
The ALICE point is the average number of Kshort
per INEL collision per unit Y at Y = 0, (1/NINEL)
dN/dY.
“Minimum Bias” Collisions
Kshort
Kshort
d s +d s
PIC 2011, Vancouver
August 29, 2011
4
Proton shortage of Kaons in PYTHIA
Proton Tune Z1!
No overall
Rick Field – Florida/CDF/CMS
d s +d s
Page 32
Kaon Production
Charged Kaons Rapidity: dN/dY
Rapidity Distribution Ratio: Kaons/Pions
Rapidity Distribution Ratio: Kshort/Kaons
0.3
0.8
0.6
ALICE Data
ALICE Data
ALICE
dN/dY
0.4
0.2
PYTHIA Tune Z1
ALICE Data
-
Kshort/(K++K-)
(K +K )
0.6
0.4
0.2
0.2
0.1
pyZ1 NSD = dashed
GeV
TuneINEL
Z1(all pT)
pyZ1 INEL900
= solid
900 GeV
INEL (all pT)
0.0
INEL (all pT)
-3
-2
-1
0
Tune Z1
900 GeV
0.0
0.0
-4
(K++K-)/(p++p-)
ALICE
PYTHIA Tune Z1
dN/dY Particle Ratio
dN/dY Particle Ratio
PYTHIA Tune Z1
+
-4 1
-3 2
-2 3
-1 4
Rapidity Y
0
-4
1
-3 2
Rapidity Y
 ALICE INEL data on the charged kaon
rapidity distribution at 900 GeV compared
with PYTHIA Tune Z1. The plot shows
the average number of charged kaons per
INEL collision per unit Y at Y = 0,
(1/NINEL) dN/dY.
-2 3
-1 4
0
1
2
3
Rapidity Y
 ALICE INEL data on the charged kaon to
charged pion rapidity ratio at 900 GeV
compared with PYTHIA Tune Z1.
“Minimum Bias” Collisions
+
K
u s
K-
Protonshortage of Kaons in PYTHIA
ProtonTune Z1!
No overall
u s
PIC 2011, Vancouver
August 29, 2011
4
Rick Field – Florida/CDF/CMS
Page 33
Particle Ratios versus PT
PT Particle Ratio: Kaons/Pions
Rapidity Distribution Ratio: Kaons/Pions
0.60
0.3
ALICE Data
+
+
-
ALICE Data
(K +K )/(p +p )
PYTHIA Tune Z1 & Z1C
(K++K-)/(p++p-)
PYTHIA Tune Z1 & Z1C
0.40
dN/dY Particle Ratio
PT Particle Ratio
-
Z1C
Z1
0.20
Tune Z1C
qq/q: 0.1 -> 0.12
us/s: 0.4 -> 0.8
900 GeV
INEL (|Y| < 0.75)
0.2
Z1C
0.1
900 GeV
INEL (all pT)
0.00
Z1
Tune Z1C
qq/q: 0.1 -> 0.12
us/s: 0.4 -> 0.8
0.0
0
1
2
PT (GeV/c)
3
4
-3
-2
-1
Tails of the pT distribution.
Way off due to the wrong pT!
 ALICE INEL data on the charged kaons to
charged pions ratio versus pT at 900 GeV (|Y|
< 0.75) compared with PYTHIA Tune Z1 &
Z1C.
0
1
2
3
K-
 ALICE INEL data on the charged kaon to
charged pion rapidity ratio at 900 GeV
compared with PYTHIA Tune Z1.
PYTHIA pT dependence off onProton
Kaons!
Proton
u s
PIC 2011, Vancouver
August 29, 2011
4
Rapidity Y
“Minimum Bias” Collisions
K+
u s
-4
Rick Field – Florida/CDF/CMS
Page 34
Lambda Production
(Lam+LamBar) Rapidity Distribution: dN/dY
0.25
Rapidity Distribution Ratio: (Lam+LamBar)/(2Kshort)
0.5
_
CMS Data
(+)
7 TeV
PYTHIA Tune Z1
dN/dY Particle Ratio
dN/dY
0.20
0.15
0.10
900 GeV
0.05
CMS
NSD (all pT)
0.00
-4
-3
-2
-1
1
_
CMS
0.4
(+)/(2Kshort)
7 TeV
0.3
0.2
Factor of 1.5!
0.1
Tune Z1
NSD (all pT)
Tune Z1
0
CMS Data
PYTHIA Tune Z1
0.0
2
3
4
-4
-3
Rapidity Y
-2
-1
0
1
2
3
4
Rapidity Y
 CMS NSD data on the Lambda+AntiLambda  CMS NSD data on the Lambda+AntiLambda
rapidity distribution at 7 TeV and 900 GeV
to 2Kshort rapidity ratio at 7 TeV compared
compared with PYTHIA Tune Z1. The plot
with PYTHIA Tune Z1.
shows the average number of particles per
NSD collision per unit Y, (1/NNSD) dN/dY.

ud s
“Minimum Bias” Collisions
Proton Tune Z1!
Oops!Proton
Not enough Lambda’s in PYTHIA
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 35
Cascade Production
Rapidity Distribution Ratio: (Cas+CasBar)/(2Kshort)
(Cas+CasBar) Rapidity Distribution: dN/dY
0.03
CMS Data

dN/dY Particle Ratio
7 TeV
dN/dY
0.02
CMS
900 GeV
0.01
PYTHIA Tune Z1
0.04
7 TeV
0.03
Factor of 2!
0.02
0.01
Tune Z1
NSD (all pT)
( + )/(2Kshort)
CMS
CMS Data

( + )
PYTHIA Tune Z1
_
0.05
_
Tune Z1
NSD (all pT)
0.00
0.00
-4
-3
-2
-1
0
1
2
3
4
-4
-3
-2
-1
0
1
2
3
4
Rapidity Y
Rapidity Y
 CMS NSD data on the Cascade CMS data on the Cascade-+AntiCascade- to
+AntiCascade- rapidity distribution at 7 TeV
2Kshort rapidity ratio at 7 TeV compared with
and 900 GeV compared with PYTHIA Tune
PYTHIA Tune Z1.
Z1. The plot shows the average number of
particles per NSD collision per unit Y,
(1/NNSD) dN/dY.
“Minimum Bias” Collisions
 
Proton Tune Z1!
Yikes! Proton
Way too few Cascade’s in PYTHIA
dss
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 36
Particle Ratios versus PT
Too many overall protons!
PT Particle Ratio: (P+Pbar)/Pions
Rapidity Distribution Ratio: (P+Pbar)/Pions
0.4
_
(p+p)/(p++p-)
ALICE Data
PYTHIA Tune Z1 & Z1C
_
(p+p)/(p++p-)
ALICE Data
PYTHIA Tune Z1 & Z1C
dN/dY Particle Ratio
PT Particle Ratio
0.12
0.3
Z1C
0.2
Z1
Tune Z1C
qq/q: 0.1 -> 0.12
us/s: 0.4 -> 0.8
0.1
900 GeV
INEL (|Y| < 0.75)
Z1C
0.09
0.06
Z1
0.03
900 GeV
INEL (all pT)
0.0
Tune Z1C
qq/q: 0.1 -> 0.12
us/s: 0.4 -> 0.8
0.00
0
1
2
PT (GeV/c)
3
4
-4
-3
Tails of the pT distribution.
Way off due to the wrong pT!
-2
-1
0
1
2
3
4
Rapidity Y
 ALICE INEL data on the Proton+AntiProton
 ALICE INEL data on the
to charged pions ratio versus pT at 900 GeV
Proton+AntiProton to charged pion rapidity
(|Y| < 0.75) compared with PYTHIA Tune Z1 &
ratio at 900 GeV compared with PYTHIA
Z1C.
Tune Z1 & Z1C.
“Minimum Bias” Collisions
p
uud
PIC 2011, Vancouver
August 29, 2011
Proton way off on the p dependence
Protonof Protons!
PYTHIA
T
Rick Field – Florida/CDF/CMS
Page 37
Fragmentation Summary
Beam-meam remnants!
Beam-meam remnants!
Charged Particle
dN/dhd
 StrangeCharged
Particle
Baryon
Particle &
Density:
dN/dhd Yields: PYTHIA is off

K+ Density:
Kshort
0.04
0.12
on RDF
thePreliminary
overall yield of Lambda’s and Cascades
RDF Preliminary u s
d s + d s(+ ud s
(p+p
(MC below the data) and too high on the0.03proton
p
0.08
 
K
yield. Difficult to fix this without destroying
0.02
uud
u s
dss
agreement
with
LEP!
0.04
0.01
7 TeV does
ND (all pT)not describe correctly the p
 PT Distributions: PYTHIA
7 TeV ND (all pT)
T distributions
0.00
0.00
of-10heavy
particles
(MC
softer
than
the
data).
None
of-4 the
fragmentation
-8
-6
-4
-2
0
2
4
6
8
10
-10
-8
-6
-2
0
2
4
6
8
10
parameters I have
looked
at changes the pT distributions.
Hence,
if one
Pseudo-Rapidity
h
Pseudo-Rapidity
h
looks at particle ratios at large pT you can see big discrepancies between
data and MC (out in the tails of the distributions)!
 Factorization: Are we seeing a breakdown in
“Minimum Bias” Collisions
+
factorization between e e annihilations and
Proton
Proton
hadron-hadron collisions! Is something
happening in hadron-hadron collisions that
does not happen in e+e- annihilations?
 Herwig++ & Sherpa: Before making any conclusions about fragmentation
one must check the predictions of Herwig++ and Sherpa carefully!
PYTHIA Tune Z1
PIC 2011, Vancouver
August 29, 2011
)
Charged Particle Density
Charged Particle Density
_
_
PYTHIA Tune Z1
Rick Field – Florida/CDF/CMS
)
Page 38
Sherpa versus PYTHIA
Strange particle production in pp at 200 GeV
(STAR_2006_S6860818)
<pT> versus Mass
 Before making any conclusion about e+eversus pp collisions one must check the
predictions of Herwig++ and Sherpa!
Sherpa does better
than PYTHIA 8!
Hendrik Hoeth
http://users.hepforge.org/~hoeth/STAR_2006_S6860818/
PIC 2011, Vancouver
August 29, 2011
Rick Field – Florida/CDF/CMS
Page 39