Northwest Terascale Workshop
Modeling Min-Bias and the Underlying Event
Min-Bias Collisions at the LHC
Rick Field
University of Florida
Part 2
 How are “min-bias” collisions related to the
“underlying event”.
 How well did we do at predicting the behavior of “min-
University of Oregon March 7-11, 2011
bias” collisions at the LHC (900 GeV and 7 TeV)?
CMS
 PYTHIA 6.4 Tune Z1: CMS tune (pT-ordered
parton showers and new MPI). Comparisons with
the LHC Min-Bias data.
“Minimum Bias” Collisions
 New Physics in Min-Bias??
Observation of long-range
same-side correlations at 7 TeV.
Proton
Proton
ATLAS
 Strange particle production:
A problem for the models?
Oregon Terascale Workshop
March 8, 2011
UE&MB@CMS
Rick Field – Florida/CDF/CMS
Page 1
Proton-Proton Collisions
Elastic Scattering
Single Diffraction
Double Diffraction
M2
M
M1
stot = sEL + sSD
IN +sDD +sHC
ND
“Inelastic Non-Diffractive Component”
Hard Core
The “hard core” component
contains both “hard” and
“soft” collisions.
“Hard” Hard Core (hard scattering)
Outgoing Parton
“Soft” Hard Core (no hard scattering)
Proton
PT(hard)
Proton
Proton
Proton
Underlying Event
Underlying Event
Initial-State
Radiation
Final-State
Radiation
Outgoing Parton
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 2
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
+…
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 3
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”.
Oregon Terascale Workshop
March 8, 2011
Proton
+
+
Proton
Proton
Rick Field – Florida/CDF/CMS
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
Page 4
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
+…
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Multiple-parton
interactions (MPI)!
Page 5
UE Tunes
Allow primary hard-scattering to
go to pT = 0 with same cut-off!
“Underlying Event”
Fit the “underlying
event” in a hard
scattering process.
Proton
Proton
All of Rick’s tunes (except X2):
1/(pT)4→ 1/(pT2+pT02)2
A, AW, AWT,DW, DWT,
D6, D6T, CW, X1,
“Min-Bias”
“Min-Bias” (add
(ND)single & double diffraction)
and Tune Z1,
are UE tunes!
Proton
Predict MB (ND)!
Proton
+
+
Proton
Proton
Proton
Single Diffraction
Predict MB (IN)!
Oregon Terascale Workshop
March 8, 2011
+…
Proton
+
Proton
Proton
Double Diffraction
M2
M
Rick Field – Florida/CDF/CMS
M1
Page 6
Charged Particle Multiplicity
Charged Multiplicity Distribution
Charged Multiplicity Distribution
1.0E+00
1.0E+00
CDF Run 2 Preliminary
1.0E-01
CDF Run 2 <Nchg>=4.5
CDF Run 2 <Nchg>=4.5
1.0E-02
Probability
Probability
1.0E-02
CDF Run 2 Preliminary
1.0E-01
1.0E-03
1.0E-04
1.0E-05
py Tune A <Nchg> = 4.3
pyAnoMPI <Nchg> = 2.6
1.0E-03
1.0E-04
1.0E-05
1.0E-06
1.0E-06
Min-Bias 1.96
1.0E-07
Min-Bias 1.96
1.0E-07
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
Normalized to 1
Normalized to 1
Charged Particles (|h|<1.0, PT>0.4 GeV/c)
1.0E-08
1.0E-08
0
5
10
15
20
25
30
35
40
45
50
55
0
5
10
Number of Charged Particles
i
20
25
30
35
40
45
50
Number of Charged Particles
“Minimum Bias” Collisions
Proton
15
No MPI!
Tune A!
AntiProton
 Data at 1.96 TeV on the charged particle multiplicity (pT > 0.4 GeV/c, |h| < 1) for “min-bias”
collisions at CDF Run 2 (non-diffractive cross-section).
 The data are compared with PYTHIA Tune A and Tune A without multiple parton
interactions (pyAnoMPI).
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 7
55
PYTHIA Tune A Min-Bias
“Soft” + ”Hard”
Charged Particle Density
1.0E+00
Pythia 6.206 Set A
CDF Min-Bias Data
Charged Density dN/dhdfdPT (1/GeV/c)
1.0E-01
Ten decades!
1.8 TeV |h|<1
1.0E-02
12% of “Min-Bias” events
have PT(hard) > 5 GeV/c!
PT(hard) > 0 GeV/c
1.0E-03
1% of “Min-Bias” events
have PT(hard) > 10 GeV/c!
1.0E-04
1.0E-05
CDF Preliminary
1.0E-06
0
2
4
6
8
PT(charged) (GeV/c)
10
12
14
Lots of “hard” scattering in
“Min-Bias” at the Tevatron!
 Comparison of PYTHIA Tune A with the pT distribution of charged particles for “min-bias”
collisions at CDF Run 1 (non-diffractive cross-section).
pT = 50 GeV/c!
 PYTHIA Tune A predicts that 12% of all “Min-Bias” events are a result of a hard 2-to-2
parton-parton scattering with PT(hard) > 5 GeV/c (1% with PT(hard) > 10 GeV/c)!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 8
CDF: Charged pT Distribution
Erratum November 18, 2010
Excess
No excess
events
atat
large
large
pTp! T!
“Minimum Bias” Collisions
Proton
AntiProton
50 GeV/c!
 Published CDF data on the pT distribution
of charged particles in Min-Bias collisions
(ND) at 1.96 TeV compared with PYTHIA
Tune A.
Oregon Terascale Workshop
March 8, 2011
CDF
CDFinconsistent
consistent with
withCMS
CMSand
andUA1!
UA1!
Rick Field – Florida/CDF/CMS
Page 9
MB Tunes
“Underlying Event”
Predict the “underlying
event” in a hard
scattering process!
Proton
Proton
Most of Peter Skand’s tunes:
S320 Perugia
0, S325 Perugia X,
“Min-Bias”
(ND)
S326 Perugia 6
are MB tunes!
Proton
Fit MB (ND).
Proton
+
Proton
+
Proton
Proton
Proton
+
Proton
Proton
+…
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 10
MB+UE Tunes
“Underlying Event”
Fit the “underlying
event” in a hard
scattering process!
Proton
Proton
Most of Hendrik’s “Professor”
tunes: ProQ20, P329
are MB+UE!
Simultaneous fit
to both MB & UE
“Min-Bias” (ND)
Proton
Fit MB (ND).
Proton
+
Proton
+…
Oregon Terascale Workshop
March 8, 2011
+
Proton
Proton
Proton
+
Proton
Proton
The ATLAS AMBT1 Tune is an MB+UE tune, but
because they include in the fit the ATLAS UE data
with PTmax > 10 GeV/c (big errors) the LHC UE data
does not have much pull (hence mostly an MB tune!).
Rick Field – Florida/CDF/CMS
Page 11
LHC MB Predictions: 900 GeV
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
5
5
RDF Preliminary
Charged Particle Density
Charged Particle Density
RDF Preliminary
4
3
2
ALICE INEL
Off by 11%!
UA5 INEL
INEL = HC+DD+SD
900 GeV
1
5
-1.5
-1.0
-0.5
0.0
4
Charged Particle Density
-2.0
2
UA5
ALICE
1
pyDW_10mm (3.04)
pyS320_10mm (3.09)
pyS320 INEL (2.70)
0
-2.5
3
NSD = HC+DD
Charged Particle Density: dN/dh
900 GeV
pyDW INEL (2.67)
Charged Particles (all pT)
-3.0
4
RDF Preliminary
0.5
1.0
1.5
0
2.0
2.5
3.0
-3.0
-2.5
-2.0 times
-1.5 1.11
-1.0
3
0.5
1.0
1.5
2.0
2.5
“Minimum Bias” Collisions
“Minimum Bias” Collisions
2
Proton
1
0.0
PseudoRapidity h
PseudoRapidity h
Proton
-0.5
INEL = HC+DD+SD
900 GeV
Charged Particles (all pT)
Proton
ALICE INEL
UA5 INEL
pyDW times 1.11 (2.97)
pyS320 times 1.11 (3.00)
Proton
0
-3.0 ALICE
-2.5 -2.0 -1.5
-1.0 with
-0.5 0.0
0.5
1.0
1.5
2.0 DW
2.5
3.0and Tune S320
 Compares the 900 GeV
data
PYTHIA
Tune
PseudoRapidity
h
Perugia 0. Tune DW uses the old Q2-ordered parton shower and the old MPI
model. Tune S320 uses the new pT-ordered parton shower and the new MPI model.
The numbers in parentheses are the average value of dN/dh for the region |h| <
0.6.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 12
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!
Oregon Terascale Workshop
March 8, 2011
Soft particles!
Rick Field – Florida/CDF/CMS
Page 13
PYTHIA Tune DW
If one increases the pT
the agreement
improves!
Charged Particle Density: dN/dh
5
Charged Particle Density
RDF Preliminary
4
At Least 1 Charged Particle |h| < 0.8
900 GeV
ALICE INEL data
pyDW generator level
pT > 0.15 GeV/c
Tune DW
3
pT > 0.5 GeV/c
2
pT > 1.0 GeV/c
1
0
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
PseudoRapidity h
 ALICE inelastic data at 900 GeV on the dN/dh distribution for charged particles (pT >
PTmin) for events with at least one charged particle with pT > PTmin and |h| < 0.8 for
PTmin = 0.15 GeV/c, 0.5 GeV/c, and 1.0 GeV/c compared with PYTHIA Tune DW at the
generator level.
“Minimum Bias” Collisions
ProtonThe
same thing occurs at 7 TeV!
Proton
ALICE, ATLAS, and CMS data coming soon.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 14
PYTHIA Tune DW
Diffraction
contributes less at
harder scales!
Charged Particle Density: dN/dh
5
Charged Particle Density
RDF Preliminary
4
At Least 1 Charged Particle |h| < 0.8
900 GeV
ALICE INEL data
pyDW generator level
pT > 0.15 GeV/c
3
Tune DW
pT > 0.5 GeV/c
2
pT > 1.0 GeV/c
1
dashed = ND solid = INEL
0
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
PseudoRapidity h
 ALICE inelastic data at 900 GeV on the dN/dh distribution for charged particles (pT >
PTmin) for events with at least one charged particle with pT > PTmin and |h| < 0.8 for
PTmin = 0.15 GeV/c, 0.5 GeV/c, and 1.0 GeV/c compared with PYTHIA Tune Z1 at the
generator level (dashed = ND, solid = INEL).
“Minimum Bias” Collisions
Proton
Cannot
trust PYTHIA 6.2 modeling of diffraction!
Proton
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 15
CMS dN/dh
Charged Particle Density: dN/dh
8
CMS
Charged Particle Density
7 TeV
6
4
RDF Preliminary
CMS NSD data
pyDW generator level
Tune DW
Soft particles!
Okay if the Monte-Carlo does not fit
dashedthe
= ND solid
= NSD
data
what do we do? All pT
0
We tune the Monte-Carlo
-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0
0.5
1.0
1.5
2.0
2.5
3.0
to fit the
data!
PseudoRapidity h
Be careful not to tune away new physics!
 Generator level dN/dh (all pT). Shows the NSD = HC + DD and the HC = ND
contributions for Tune DW. Also shows the CMS NSD data.
2
“Minimum Bias” Collisions
Proton
Oregon Terascale Workshop
March 8, 2011
Off by 50%!
Rick Field – Florida/CDF/CMS
Proton
Page 16
CMS dN/dh
Charged Particle Density: dN/dh
Charged Particle Density: dN/dh
8
RDF Preliminary
RDF Preliminary
Charged Particle Density
Charged Particle Density
8
6
Tune Z1
4
CMS
2
CMS NSD 7 TeV
7 TeV
pyZ1 HC (6.51)
pyZ1 NSD (5.58)
0
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
6
4
CMS
2
CMS NSD 7 TeV
7 TeV
pyX2 NSD (5.91)
pyZ1 NSD (5.58)
CMS NSD all pT
0
-3.0
-2.5
-2.0
PseudoRapidity h
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
PseudoRapidity h
 Generator level dN/dh (all pT). Shows
the NSD = HC + DD and the HC = ND
contributions for Tune Z1. Also shows
the CMS NSD data.
 Generator level dN/dh (all pT). Shows
the NSD = HC + DD prediction for
Tune Z1 and Tune X2. Also shows the
CMS NSD data.
“Minimum Bias” Collisions
Okay not perfect, but remember
Proton
we do not know if the DD is correct!
Proton
Oregon Terascale Workshop
March 8, 2011
3.0
Rick Field – Florida/CDF/CMS
Page 17
PYTHIA Tune Z1
Charged Particle Density: dN/dh
5
Charged Particle Density
RDF Preliminary
4
ALICE INEL data
pyZ1 generator level
At Least 1 Charged Particle |h| < 0.8
900 GeV
pT > 0.15 GeV/c
3
pT > 0.5 GeV/c
2
pT > 1.0 GeV/c
1
0
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
PseudoRapidity h
 ALICE inelastic data at 900 GeV on the dN/dh distribution for charged particles (pT >
PTmin) for events with at least one charged particle with pT > PTmin and |h| < 0.8 for
PTmin = 0.15 GeV/c, 0.5 GeV/c, and 1.0 GeV/c compared with PYTHIA Tune Z1 at the
generator level.
“Minumum Bias” Collisions
Okay
not perfect, but remember
Proton
Proton
we do not know if the SD & DD are correct!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 18
7 TeV dN/dh
Min-Bias Common Charged
PlotsParticle Density Ratio: dN/dh
Charged Particle Density: dN/dh
4
1.20
7 TeV
At Least 1 Charged Particle |h| < 0.8
CMS INEL data
pyZ1 generator level
pT > 0.5 GeV/c
3
2
1
At Least 1 Charged Particle |h| < 0.8
Corrected INEL data
1.10
pT > 0.5 GeV/c
1.05
1.00
0.95
0.90
7 TeV
0.85
CMS = solid squares ATLAS = solid circle
-2.5
MB&UE Preliminary
1.15
Charged Particle Ratio
Charged Particle Density
MB&UE Preliminary
CMS divided by ATLAS (red)
0.80
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
-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
 Corrected data from CMS and ATLAS at 7 TeV for dN/dh (pT > PTmin, direct charged
particles including leptons with no corrections for SD or DD) with at least one charged particle
with pT > PTmin and |h| < 0.8 for PTmin = 0.5 GeV/c compared with PYTHIA Tune Z1.
 Ratio of the corrected data from CMS and ATLAS at 7 TeV for dN/dh (pT > PTmin) with at
least one charged particle with pT > PTmin and |h| < 0.8 for PTmin = 0.5 GeV/c. CMS divided
by ATLAS.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 19
7 TeV dN/dh
Min-Bias Common Charged
PlotsParticle Density Ratio: dN/dh
Charged Particle Density: dN/dh
1.20
3
7 TeV
At Least 1 Charged Particle |h| < 0.8
CMS INEL data
pyZ1 generator level
MB&UE Preliminary
1.15
Charged Particle Ratio
Charged Particle Density
MB&UE Preliminary
pT > 1.0 GeV/c
2
1
1.10
pT > 1.0 GeV/c
1.05
1.00
0.95
0.90
7 TeV
0.85
CMS = solid squares ATLAS = solid circle
At Least 1 Charged Particle |h| < 0.8
Corrected INEL data
CMS divided by ATLAS (red)
0.80
0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
PseudoRapidity h
PseudoRapidity h
 Corrected data from CMS and ATLAS at 7 TeV for dN/dh (pT > PTmin, direct charged
particles including leptons with no corrections for SD or DD) with at least one charged particle
with pT > PTmin and |h| < 0.8 for PTmin = 1.0 GeV/c compared with PYTHIA Tune Z1
 Ratio of the corrected data from CMS and ATLAS at 7 TeV for dN/dh (pT > PTmin) with at
least one charged particle with pT > PTmin and |h| < 0.8 for PTmin = 1.0 GeV/c. CMS divided
by ATLAS.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 20
900 GeV dN/dh
Min-Bias Common Charged
PlotsParticle Density Ratio: dN/dh
Charged Particle Density: dN/dh
1.20
MB&UE Preliminary
At Least 1 Charged Particle |h| < 0.8
1.8
pT > 0.5 GeV/c
1.6
1.4
1.2
900 GeV
CMS = solid squares ALICE = open squares ATLAS = solid circle
At Least 1 Charged Particle |h| < 0.8
Corrected INEL data
1.10
pT > 0.5 GeV/c
1.05
1.00
0.95
0.90
CMS divided by ALICE (blue)
900 GeV
0.85
1.0
-2.5
MB&UE Preliminary
1.15
Corrected INEL data
pyZ1 generator level
Charged Particle Ratio
Charged Particle Density
2.0
CMS divided by ATLAS (red)
0.80
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
-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
 Corrected data from CMS, ATLAS, and ALICE at 900 GeV for dN/dh (pT > PTmin, direct
charged particles including leptons with no corrections for SD or DD) with at least one charged
particle with pT > PTmin and |h| < 0.8 for PTmin = 0.5 GeV/c compared with PYTHIA Tune
Z1
 Ratio of the corrected data from CMS, ATLAS, and ALICE at 900 GeV for dN/dh (pT >
PTmin) with at least one charged particle with pT > PTmin and |h| < 0.8 for PTmin = 0.5
GeV/c. CMS divided by ATLAS and CMS divided by ALICE.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 21
900 GeV dN/dh
Min-Bias Common Charged
PlotsParticle Density Ratio: dN/dh
Charged Particle Density: dN/dh
1.20
MB&UE Preliminary
1.0
Corrected INEL data
pyZ1 generator level
Charged Particle Density
Charged Particle Density
1.2
pT > 1.0 GeV/c
0.8
0.6
0.4
900 GeV
At Least 1 Charged Particle |h| < 0.8
1.15
MB&UE Preliminary
At Least 1 Charged Particle |h| < 0.8
Corrected INEL data
1.10
pT > 1.0 GeV/c
1.05
1.00
0.95
0.90
CMS divided by ALICE (blue)
900 GeV
0.85
CMS divided by ATLAS (red)
CMS = solid squares ALICE = open squares ATLAS = solid circle
0.80
0.2
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
PseudoRapidity h
PseudoRapidity h
 Corrected data from CMS, ATLAS, and ALICE at 900 GeV for dN/dh (pT > PTmin, direct
charged particles including leptons with no corrections for SD or DD) with at least one charged
particle with pT > PTmin and |h| < 0.8 for PTmin = 1.0 GeV/c compared with PYTHIA Tune
Z1
 Ratio of the corrected data from CMS, ATLAS, and ALICE at 900 GeV for dN/dh (pT >
PTmin) with at least one charged particle with pT > PTmin and |h| < 0.8 for PTmin = 1.0
GeV/c. CMS divided by ATLAS and CMS divided by ALICE.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 22
dN/dh |h| < 2.4 (2.5)
Charged Particle Density: dN/dh
Charged
4
2
1
-2.5
-2.0
-1.5
900 GeV
1.01
pT > 1.0 GeV/c
1.00
CMS = solid points ATLAS = open squares
0
-1.0
-0.5
0.99
0.0
At Least 1 Charged Particle |h| < 2.4 or 2.5
Corrected INEL data
At Least 1 Charged
Particle |h| < 2.4 (2.5)
pT generator
> 0.5 GeV/clevel
pyZ1
1.02
Charged Particle Density
MB&UE Preliminary
Corrected INEL data
pyZ1 generator level
7 TeV
MB&UE Preliminary
At Least 1 Charged Particle |h| < 2.4 or 2.5
Charged Particle Ratio
Charged Particle Density
2.0
1.03
MB&UE Preliminary
3
Particle Density Ratio:Charged
dN/dhParticle Density: dN/dh
pyZ1 generator level
1.5
pT > 0.5 GeV/c
pT > 0.5 GeV/c
1.0
pT > 1.0 GeV/c
0.5
7 TeV
900 GeV
CMS = solid points ATLAS = open squares
0.0
0.5
1.0
1.5
2.0
2.5
|h| < 2.4 divided by |h| < 2.5
PseudoRapidity h
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
PseudoRapidity h
0.98
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
than 1% difference
for CMS at 7 TeV for dN/dh
Less
Corrected
data from
(pT > PTmin,
PseudoRapidity
h direct charged particles including
|h|
<
2.4
and
|h|
<
2.5!
leptons with no corrections for SD or DD) with at least one charged particle with pT > PTmin
and |h| < 2.4 for PTmin = 0.5 GeV/c and 1.0 GeV/c compared with PYTHIA Tune Z1. Also
shows the ATLAS data |h| < 2.5 PTmin = 0.5 GeV/c.
 Corrected data from CMS at 900 GeV for dN/dh (pT > PTmin) with at least one charged
particle with pT > PTmin and |h| < 2.4 for PTmin = 0.5 GeV/c and 1.0 GeV/c compared with
PYTHIA Tune Z1. Also shows the ATLAS data |h| < 2.5 PTmin = 0.5 GeV/c.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 23
Other Comparisons 7 TeV
Direct charged particles (including leptons) corrected to
the particle level with no corrections for SD or DD.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 24
Interesting Ratios
Charged Particle Ratio: dN/dh
Charged Particle Ratio: dN/dh
0.6
2.5
CMS Preliminary
At Least 1 Charged Particle |h| < 2.4
Corrected INEL data
0.5
Charged Particle Ratio
Charged Particle Ratio
CMS Preliminary
7 TeV
pyZ1 generator level
0.4
900 GeV
0.3
-2.5
pT > 1.0 GeV/c
pyZ1 generator level
2.0
1.5
pT > 0.5 GeV/c
7 TeV divided by 900 GeV
pT > 1.0 GeV divided by pT > 0.5 GeV/c
0.2
At Least 1 Charged Particle |h| < 2.4
Corrected INEL data
1.0
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
-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
Measure of the pT dependence!
Measure of the energy dependence!
 Corrected data from CMS at 7 TeV and 900 GeV for dN/dh (pT > PTmin, direct charged
particles including leptons with no corrections for SD or DD) with at least one charged particle
with pT > PTmin and |h| < 0.8 for PTmin = 1.0 GeV/c compared with PYTHIA Tune Z1. The
plot shows PTmin = 1.0 GeV/c divided by PTmin = 0.5 GeV/c at 900 GeV and 7 TeV.
 Corrected data from CMS at 7 TeV and 900 GeV for dN/dh (pT > PTmin, direct charged
particles including leptons with no corrections for SD or DD) with at least one charged particle
with pT > PTmin and |h| < 0.8 for PTmin = 1.0 GeV/c compared with PYTHIA Tune Z1. The
plot shows 7 TeV divided by 900 GeV for PTmin = 0.5 GeV/c and 1.0 GeV/c.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 25
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
Oregon Terascale Workshop
March 8, 2011
Okay not perfect!
But not that bad!
Rick Field – Florida/CDF/CMS
Proton
Page 26
MB & UE
"Transverse" Charged Particle Multiplicity
Charged Multiplicity Distribution
1.0E+00
1.0E-01
“Min-Bias”
RDF Preliminary
PT(chgjet#1) > 3 GeV/c
data CMS NSD
pyZ1 generator level
CMS
1.0E-02
Probability
Probability
data uncorrected
pyZ1 + SIM
1.0E-01
CMS
1.0E-02
CMS Preliminary
7 TeV
Tune Z1
1.0E-03
7 TeV
900 GeV
1.0E-04
900 GeV
1.0E-03
“Underlying Event”
1.0E-05
Normalized to 1
Charged Particles
(all PT, |h|<2.0)
1.0E-04
0
20
1.0E-06
Difficult to produce
40
60
80
enough
events
with
Number of Charged Particles
large multiplicity!
1.0E-07
0
100
 Generator level charged multiplicity
distribution (all pT, |h| < 2) at 900 GeV
and 7 TeV. Shows the NSD = HC + DD
prediction for Tune Z1. Also shows the
CMS NSD data.
Oregon Terascale Workshop
March 8, 2011
Charged Particles (|h|<2.0, PT>0.5 GeV/c)
Tune Z1
5
10
15
20
25
30
35
40
Number of Charged Particles
 CMS uncorrected
Difficult
datatoatproduce
900 GeV and 7
TeV on the charged
enoughparticle
events with
multiplicity
distribution inlarge
the “transverse”
“transverse” region
for charged particles
multiplicity
(pT >at0.5
low
GeV/c, |h|
< 2) as defined byhard
the leading
scale! charged
particle jet with PT(chgjet#1) > 3 GeV/c
compared with PYTHIA Tune Z1 at the
detector level (i.e. Theory + SIM).
Rick Field – Florida/CDF/CMS
Page 27
MB & UE
ChargedParticle
ParticleMultiplicity
Multiplicity
Charged
1.0E+00
1.0E+00
CMS
TeV
77 TeV
CMS Preliminary
Preliminary
CMS
Tune Z1
Z1
Tune
Min-Bias
NSD All pT
1.0E-01
1.0E-01
Probability
Probability
Min-Bias
NSD All pT
1.0E-02
1.0E-02
Underlying Event
"Transverse" Region
pT > 0.5 GeV/c
PT(chgjet#1) > 20 GeV/c
1.0E-03
1.0E-03
1.0E-04
1.0E-04
Normalizedto
to11
Normalized
Underlying Event
"Transverse" Region
pT > 0.5 GeV/c
PT(chgjet#1) > 20 GeV/c
Tune Z1
Charged Particles (|h|<2.0)
Charged Particles (|h|<2.0)
1.0E-05
1.0E-05
00
5
2010
1540
20
60
25
30 80 35
100
40
Number of
of Charged
Charged Particles
Particles
Number
 CMS uncorrected data at 7 TeV on the charged particle multiplicity distribution in the
“transverse” region for charged particles (pT > 0.5 GeV/c, |h| < 2) as defined by the leading
charged particle jet with PT(chgjet#1) > 20 GeV/c compared with PYTHIA Tune Z1 at the
detector level (i.e. Theory + SIM). Also shows the CMS corrected NSD multiplicity
distribution (all pT, |h| < 2) compared with Tune Z1 at the generator.
Amazing what we are asking the Monte-Carlo models to fit!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 28
New Physics in “Min-Bias”?
“Semi-hard” partonparton collision
(pT < ≈2 GeV/c)
The Inelastic Cross Section
Proton
Proton
+
Proton
+
Proton
Proton
Proton
+
Proton
Proton
+…
Multiple-parton
interactions (MPI)!
CMS Two-Particle Correlations at 7 TeV.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 29
Two Particle Angular Correlations
 Signal, S, is two particles in the
same event.
 Background, B, is two particles in
two different events.
“Minimum Bias” Collisions
Proton
Proton
 Correlation, R, is ~(S-B)/B.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 30
Two Particle Angular Correlations
CMS “min-bias” 7 TeV
x-axis
Bose-Einstein
Two Particles in Two Jets
y-axis
Jet#2
Jet#1
x-axis
Two Particles in Same Jet
y-axis
Jet#2
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Jet#1
Page 31
High Multiplicity at 7 TeV
Select Events with High Multiplicity
“Minimum Bias” Collisions
Proton
Oregon Terascale Workshop
March 8, 2011
Proton
Rick Field – Florida/CDF/CMS
Page 32
Two Particle Angular Correlations
High Multiplicity “Min-Bias”
Average “Min-Bias”
x-axis
Two Particles in Same Jet
y-axis
Jet#2
Jet#1
Lots of jets at high multiplicity!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 33
Two Particle Angular Correlations
High Multiplicity “Min-Bias”
Average “Min-Bias”
x-axis
Two Particles in Two Jets
y-axis
Jet#2
Oregon Terascale Workshop
March 8, 2011
Jet#1
Rick Field – Florida/CDF/CMS
Page 34
Long-Range Same-Side
Correlations
High Multiplicity “Min-Bias”
Not there in PYTHIA8!
Oregon Terascale Workshop
March 8, 2011
High Multiplicity “Min-Bias”
Also not there in PYTHIA 6 and HERWIG++!
Rick Field – Florida/CDF/CMS
Page 35
Correlation in Heavy Ion
Collisions
Long range correlations expected in “collective flow” in heavy ion collisions.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 36
Correlation in Heavy Ion
Collisions
Long-range “Ridge”-like structure in Dh at Df ≈ 0!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 37
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!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 38
Jet-Jet Correlations
 Are the “leading-log” or “modified leading-log” QCD Monte-Carlo Models missing
x-axis
an important QCD correlation?
 The leading jet and the incident protons
form a plane (yz-plane in the figure). This
is the plane of the hard scattering.
Proton
Proton
z-axis
Initial or FinalState Radiation
Leading Jet
y-axis
 Initial & final-state radiation prefers to lie in this plane. This is a higher order
effect that you can see in the 2→3 or 2→4 matrix elements, but it is not there if
you do 2→2 matrix elements and then add radiation using a naïve leading log
approximation (i.e. independent emission).
 I do not know to what extent this higher order jet-jet correlation is incorporated in
the QCD Monte-Carlo models.
 I would think that this jet-jet correlation would produce a long range (in Dh)
correlation with Df ≈ 0 from two particles with one in the leading jet and one in the
radiated jet. Why don’t we see this in the Monte-Carlo models?
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 39
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?
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 40
High Multiplicity at 7 TeV
Select Events with High Multiplicity
“Minimum Bias” Collisions
Proton
Proton
We need to study the structure of the high multiplicity
min-bias events! Does high multiplicity imply high PT
jets? Are there a class of “soft” high multiplicity
events? If so what is the source of these events?
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 41
Strange Particle Production
Factor of 2!
ALICE preliminary
stat. error only
Jan Fiete Grosse-Oetringhaus
LPCC MB&UE Meeting
September 2010
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.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 42
Charged Particle dN/dh 7 TeV
Charged Particle Density: dN/dh
Charged Particle
Particle Density:
Density: dN/dh
dN/dh
Charged
8
810.000
PYTHIA Tune Z1 7 TeV
All pT
ChargedParticle
ParticleDensity
Ratio
Charged
Charged Particle Density
PYTHIA Tune Z1 ND 7 TeV
pT > 0.5 GeV/c
6
pT > 1.0 GeV/c
4
2
0
INEL
6 1.000
All All
pT pT
pT > 0.5 GeV/c
pT > 1.0 GeV/c
pT > 2.0 GeV/c
4 0.100
ND
pT >3.0 GeV/c
DD
2 0.010
SD
PYTHIA Tune Z1 ND 7 TeV
0 0.001
-10
-8
-6
-4
-2
0
2
4
6
8
10
-10
-10-8
-8 -6
PseudoRapidity h
-6 -4
-4 -2 -2
0 0
2 2
44
66
88
10
10
PseudoRapidity
PseudoRapidity
h h
 Charged particle (direct, including leptons) pseudorapidity distribution, dN/dh (ND), at 7 TeV for all
pT, pT > 0.5 GeV/c, pT > 1.0 GeV/c, pT > 2.0 GeV/c, and pT > 3.0 GeV/c from Tune Z1.
 Charged particle (direct, including leptons) pseudorapidity distribution, dN/dh, at 7 TeV for all pT
from Tune Z1. Shows the individual contributions from ND, SD, DD, and INEL = ND + SD + DD.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 43
Charged Particle dN/dh 7 TeV
Charged Particle Ratio: Flavor/All Charged
1.2
sum
1.2
All pT
1.0
0.8
p+ + p-
0.6
0.4
K + + K-
proton
sum
PYTHIA Tune Z1 7 TeV INEL
Charged Particle Ratio
Charged Particle Ratio
PYTHIA Tune Z1 7 TeV ND
Charged Particle Ratio: Flavor/All Charged
Antiproton
0.2
0.0
All pT
1.0
0.8
p+ + p-
0.6
proton
0.4
K + + K-
Antiproton
0.2
0.0
-10
-8
-6
-4
-2
0
2
4
6
8
10
-10
-8
PseudoRapidity h
-6
-4
-2
0
2
4
6
8
10
PseudoRapidity h
 Charged particle ratios versus h at 7 TeV (ND all pT). Shows (p+ +p-)/(all charged), (K+ + K-)/(all
charged), proton/(all charged), antiproton/(all charged), and sum/(all charged), where sum = p+ + p+ K+ + K- + p + pbar.
 Charged particle ratios versus h at 7 TeV (INEL = ND + SD +DD all pT). Shows (p+ +p-)/(all
charged), (K+ + K-)/(all charged), proton/(all charged), antiproton/(all charged), and sum/(all
charged), where sum = p+ + p- + K+ + K- + p + pbar.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 44
Charged Particle dN/dh 7 TeV
Charged Particle
Particle Ratio:
Ratio: Flavor/All
Flavor/All Charged
Charged
Charged
ChargedParticle
ParticleRatio:
Ratio:Flavor/All
Flavor/AllCharged
Charged
Charged
1.2
1.2
1.2
sum
sum
sum
pTGeV/c
pT All
1.0
pT
>> 3.0
GeV/c
1.0
1.0
1.0
Charged
ChargedParticle
ParticleRatio
Ratio
Charged
Charged Particle
Particle Ratio
Ratio
PYTHIA
PYTHIA Tune
Tune Z1
Z1 77 TeV
TeV ND
ND
1.2
1.2
p+ + p-
0.8
0.8
0.8
p+ + p-
0.6
0.6
0.6
p +p
+
0.4
0.4
0.4
++ + K
Antiproton
KK
+ KK- + + K-Antiproton
Antiproton
proton
proton
proton
0.2
0.2
0.2
0.0
0.0
0.0
-10
-10
-10
1.0
1.0
PYTHIA Tune Z1 7 TeV ND
PYTHIA Tune Z1 7 TeV ND
sum
sum
pT0.5
> 2.0
GeV/c
pT >
GeV/c
p+ + p-
0.8
0.8
0.6
0.6
+
proton p + p
Antiproton
Antiproton
K+ + K K+ + K -
0.4
0.4
proton
0.2
0.2
0.0
0.0
-8
-8
-8
-6
-6
-6
-4
-4
-4
-2
-2
-2
000
222
444
666
888
10
10
10
-10
-10
-8
-8
-6
-6
-4
-4
-2
-2
00
22
44
66
88
10
10
PseudoRapidityhh
PseudoRapidity
PseudoRapidityhhh
PseudoRapidity
PseudoRapidity
 Charged particle ratios versus h at 7 TeV (ND all pT). Shows (p+ +p-)/(all charged), (K+ + K-)/(all
charged), proton/(all charged), antiproton/(all charged), and sum/(all charged), where sum = p+ + p+ K+ + K- + p + pbar.
 Charged particle ratios versus h at 7 TeV (ND pT > 0.5 GeV/c). Shows (p+ +p-)/(all charged), (K+ +
K-)/(all charged), proton/(all charged), antiproton/(all charged), and sum/(all charged), where sum
= p+ + p- + K+ + K- + p + pbar.
 Charged particle ratios versus h at 7 TeV (ND pT > 1.0 GeV/c). Shows (p+ +p-)/(all charged), (K+ +
K-)/(all charged), proton/(all charged), antiproton/(all charged), and sum/(all charged), where sum
= p+ + p- + K+ + K- + p + pbar.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 45
Charged Particle Ratios
Charged Particle
Particle Ratio:
Ratio: Flavor/All
Flavor/All Charged
Charged
Charged
sum
sum
PYTHIA Tune
Tune Z1
Z1 77 TeV
TeV INEL
ND0.6
PYTHIA
1.0
1.0
0.6
0.6
+
-
K +K
K+ + K-
0.4
0.4
0.2
0.2
0.0
0.0
00
11
Strange Particle Ratio
PYTHIA Tune Z1 7 TeV
0.8
0.8
+
p0.5
+ pp+ + p-
0.4
pp++pbar
pbar
0.3
sum
PYTHIA Tune Z1 7 TeV ND
2
|h||h|< <0.8
Charged Particle Ratio
1.2
1.2
Charged
Charged Particle
Particle Ratio
Ratio
Charged Particle Ratio: Flavor/All Charged
Strange Particle Ratio:1.2
(K+ + K-)/(p+ + p-)
1.0
|h| < 0.8
|h| < 0.8
0.8
p+ + p-
0.6
K+ + K-
0.4
p + pbar
0.2
0.2
0.0
220.1
PT (GeV/c)
(GeV/c)
PT
33
44
55
0
1
2
3
4
5
ND = open squares INEL = black dotsPT (GeV/c)
0.0
-)/(all charged),
2.0 (p+ +p2.5
3.0
 Charged particle ratios 0.0
versus pT0.5at 7 TeV1.0(ND |h| 1.5
< 2). Shows
(K+ + K-)/(all
(GeV/c) where sum = p+ + p- + K+ + K- + p + pbar.
charged), (p + pbar)/(all charged), and sum/(allPT
charged),
 Charged particle ratios versus pT at 7 TeV (ND |h| < 0.8). Shows (p+ +p-)/(all charged), (K+ + K-)/(all
charged), (p + pbar)/(all charged), and sum/(all charged), where sum = p+ + p- + K+ + K- + p + pbar.
 Charged particle ratios versus pT at 7 TeV (INEL |h| < 0.8). Shows (p+ +p-)/(all charged), (K+ + K)/(all charged), (p + pbar)/(all charged), and sum/(all charged), where sum = p+ + p- + K+ + K- + p +
pbar.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 46
Charged Particle Ratios
Charged Particle Ratio: Flavor/All Charged
Charged
Particle
Charged
Particle
Ratio: Density:
Flavor/AlldN/dh
Charged
+
Strange Particle Ratio: (K
+ K-)/(p+ + p-)
1.2
8
1.2
sum
7 TeVAll pT
1.0
6
0.8
All pT
Strange Particle Ratio
PYTHIA Tune Z1 ND
0.5
p+ + 0.4
p-
4
0.6
0.4
2
0.2
proton
K + + K-
0.3
Antiproton
900 GeV
0
0.0
-10
-8
-6
-4
-4
sum
PYTHIA Tune Z1 900 GeV ND
Charged Particle Ratio
Charged Particle Ratio
Charged Particle Density
PYTHIA
TeV ND0.6
PYTHIATune
Tune Z1
Z1 7ND
1.0
All pT
|h| < 0.8
0.8
p+ + p-
0.6
0.4
K + + K-
proton
Antiproton
0.2
0.2
0.0
-20.1
-2
00
22
PseudoRapidityhh
PseudoRapidity
44
66
88
1010
-10
-8
-6
-4
-2
0
2
4
6
8
10
900 GeV = open squares
PseudoRapidity h
7 TeV = black dots
0.0
0.0 including
0.5
1.0 pseudorapidity
1.5
2.0 distribution,
2.5
3.0
 Charged particle (direct,
leptons)
dN/dh
(ND all pT), at 7 TeV
PT (GeV/c)
and 900 GeV from Tune Z1.
 Charged particle ratios versus h at 900 GeV (ND all pT). Shows (p+ +p-)/(all charged), (K+ + K-)/(all
charged), proton/(all charged), antiproton/(all charged), and sum/(all charged), where sum = p+ + p+ K+ + K- + p + pbar.
 Charged particle ratios versus h at 7 TeV (ND all pT). Shows (p+ +p-)/(all charged), (K+ + K-)/(all
charged), proton/(all charged), antiproton/(all charged), and sum/(all charged), where sum = p+ + p+ K+ + K- + p + pbar.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 47
Strange Particle Production
Strange Particle Ratio: (K+ + K-)/(p+ + p-)
0.6
PYTHIA Tune Z1 ND 900 GeV
|h| < 0.8
Factor of 2!
Strange Particle Ratio
0.5
Plateau!
0.4
0.3
0.2
0.1
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
PT (GeV/c)
 A lot more strange mesons at large pT than predicted by the Monte-Carlo
Models and a different shape of the curve!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 48
PYTHIA Fragmentation
Parameters
 PARJ(1) : (D = 0.10) is P(qq)/P(q), the suppression of diquark-antidiquark pair production in
the colour field, compared with quark–antiquark production.
 PARJ(2) : (D = 0.30) is P(s)/P(u), the suppression of s quark pair production in the field
compared with u or d pair production.
 PARJ(3) : (D = 0.4) is (P(us)/P(ud))/(P(s)/P(d)), the extra suppression of strange diquark
production compared with the normal suppression of strange quarks.
 PARJ(4) : (D = 0.05) is (1/3)P(ud1)/P(ud0), the suppression of spin 1 diquarks compared with
spin 0 ones (excluding the factor 3 coming from spin counting).
Look at the affect of
changing PARJ(2)
from 0.3 to 0.5!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 49
Charged Particle Ratios
Charged
Particle
Ratio:Density:
Flavor/All
Charged
Charged
Particle
dN/dh
Charged
Particle
Ratio:
Flavor/All
Charged
1.2
8
1.2
All pT
0.0
0
0.0
0
-10
-10
0.5
p+ + p-
p+ + p0.4
0.6
4
0.6
0.4
0.4
2
0.2
0.2
Strange Particle Ratio
PYTHIA Tune Z1 ND 900 GeV
s/u = 0.5
+
-
K +proton
K
-8-8
-6-61
-4
-4
0.3
sum
sum
PYTHIA
= 0.5
PYTHIA Tune
Tune Z1
Z1 77 TeV
TeV ND
ND s/u
(s/u=0.5)
Charged
Charged Particle
Particle Ratio
Ratio
1.0
1.0
6
0.8
0.8
1.2
sum
sum s/u = 0.3
All|h|
pT< 0.8
(default)
PYTHIA
Tune
Z1
ND0.6
PYTHIA
Tune
77 TeV
ND
PYTHIA
Tune
Z1Z1
ND
7TeV
TeV
Charged
Particle
Ratio
Charged
ChargedParticle
ParticleDensity
Ratio
Charged Particle
Particle Ratio:
Ratio: Flavor/All
Flavor/All Charged
Charged
Charged
Strange Particle Ratio: 1.2
(K+ + K-)/(p+ + p-)
s/u = 0.5
K+ + Kp- + pbar
Antiproton
0.2
1.0
1.0
All pT
|h| < 0.8
|h| < 0.8
0.8
0.8
p+ + p-
0.6
0.6
p+ + pK+ proton
+ K-
0.4
0.4
Antiproton
K+ + K- p + pbar
0.2
0.2
0.0
0.0
s/u
= 0.3 (default)
-2
-220.1 00
223
4
64
88
105
10
0
-10
-8
PT (GeV/c) hh
PseudoRapidity
PseudoRapidity
-61
-4
-22
0
23
4
64
8
105
PT (GeV/c) h
PseudoRapidity
0.0
0.5 leptons)
1.0 pseudorapidity
1.5
2.0
2.5
3.0 (ND all pT), at 7 TeV
 Charged particle (direct,0.0including
distribution,
dN/dh
(GeV/c)
for PARJ(2) = s/u = 0.3 (default) and PARJ(2) =PTs/u
= 0.5 from Tune Z1.
 Charged particle ratios versus h at 7 TeV (ND all pT) with PARJ(2) = s/u = 0.3 (default) and
PARJ(2) = s/u = 0.5 from Tune Z1. Shows (p+ +p-)/(all charged), (K+ + K-)/(all charged), proton/(all
charged), antiproton/(all charged), and sum/(all charged), where sum = p+ + p- + K+ + K- + p +
pbar.
 Charged particle ratios versus pT at 7 TeV (ND |h| < 0.8) with PARJ(2) = s/u = 0.3 (default) and
PARJ(2) = s/u = 0.5 from Tune Z1. Shows (p+ +p-)/(all charged), (K+ + K-)/(all charged), (p +
pbar)/(all charged), and sum/(all charged), where sum = p+ + p- + K+ + K- + p + pbar.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 50
Strange Particle Production
Not good!
Strange Particle Ratio: (K+ + K-)/(p+ + p-)
0.6
Plateau!
PYTHIA Tune Z1 ND 900 GeV
|h| < 0.8
Strange Particle Ratio
0.5
0.4
0.3
0.2
s/u = 0.5
0.1
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
PT (GeV/c)
 A lot more strange mesons at large pT than predicted by the Monte-Carlo Models and a
different shape of the curve!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 51
Protons & Antiprotons
Proton+AntiP Ratio: (p+pbar)/(p+ + p-)
ALICE preliminary
stat. error only
0.35
PYTHIA Tune Z1 ND 900 GeV
|h| < 0.8
Jan Fiete Grosse-Oetringhaus
LPCC MB&UE Meeting
September 2010
Baryon Particle Ratio
0.30
0.25
0.20
0.15
Phojet
Pythia ATLAS-CSC
Pythia D6T
Pythia Perugia-0
0.10
0.05
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
PT (GeV/c)
 Tune Z1 (ND) does not get this right either and this curve does not depend on PARJ(2)!
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 52
“Transverse” Particle Ratios
Leading Particle Ratio: Flavor/All Charged
1.2
1.2
sum
PYTHIA Tune Z1 7 TeV ND
|h| < 2
PYTHIA Tune Z1 7 TeV ND
1.0
Charged Particle Ratio
Charged Particle Ratio
"Transverse" Ratio: Flavor/All Charged
PTmax Direction
p+ + p-
0.8
0.6
+
K +K
0.4
-
p + pbar
0.2
1.0
Df
sum
|h| < 2 pT > 0.5 GeV/c
“Toward”
0.8
0.6
“Transverse”
0.4
p+ + p“Transverse”
p + pbar
K + + K-
“Away”
0.2
0.0
0.0
0
2
4
6
8
10
0
2
4
6
8
10
PTmax (GeV/c)
PTmax (GeV/c)
 Leading charged particle ratios versus pT at 7 TeV (|h| < 2.0). Shows (p+ +p-)/(all charged), (K+ + K)/(all charged), (p + pbar)/(all charged), and sum/(all charged), where sum = p+ + p- + K+ + K- + p +
pbar.
 Charged particle ratios in the “transverse” region (pT > 0.5 GeV/c, |h| < 2.0) versus the leading
charged particle, PTmax, at 7 TeV. Shows (p+ +p-)/(all charged), (K+ + K-)/(all charged), (p +
pbar)/(all charged), and sum/(all charged), where sum = p+ + p- + K+ + K- + p + pbar.
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 53
Summary
So far no luck at fitting the min-bias charged kaon to charged pion ratio.
Increasing s/u produces more strange particles, but the shape of the curve
versus pT is different! But I am just getting started at this!
Also not getting the protons + antiprotons right. Changing PARJ(2) does
nothing here! Must check out some of the other parameters
The Monte-Carlo models are constrained by LEP data. Must make sure that
I do not destroy the agreement with the LEP data!
We need a better understanding and modeling of diffraction!
protons
Diffraction
antiprotonss
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 54
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 “min-bias” 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! Also not getting the protons + antiprotons right! The MonteCarlo models are constrained by LEP data.
Color
Diffraction
Connections
Oregon Terascale Workshop
March 8, 2011
Rick Field – Florida/CDF/CMS
Page 55