Transcript b-Quark Production at the Tevatron  I believe it is important to have good “leading-log” order QCD Monte-Carlo model predictions of collider observables.

b-Quark Production
at the Tevatron
 I believe it is important to have good “leading-log” order QCD Monte-Carlo model
predictions of collider observables. The “leading-log” QCD Monte-Carlo model estimates
are the “base line” from which other calculations can be compared.
 I see no reason why the QCD “leading-log” Monte-Carlo models should not qualitatively
describe heavy quark production (in the same way they qualitatively describe light quark and
gluon production).
 We measure hadrons & leptons (NOT quarks & gluons) and hadronization effects are
important! The QCD “leading-log” Monte-Carlo models incorporate fragmentation via
“string fragmentation” or “cluster fragmentation” or “FF fragmentation” thus producing
hadrons and leptons.
 At “leading-log” order the sources of b-quarks can be divided into three categories: “flavor
creation”, “flavor excitation”, “shower/fragmentation” (i.e. “gluon splitting”).
“Flavor Creation”
“Flavor Excitation”
b-quark
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
b-quark
Proton
“Parton Shower/Fragmentation”
b-quark
AntiProton
Underlying Event
Underlying Event
b-quark
Initial-State
Radiation
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
gluon, quark,
or antiquark
b-quark
b-quark
All three sources are important at the Tevatron!
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 1
b-Quark Production
at the Tevatron
 I believe it is important to have good “leading-log” order QCD Monte-Carlo model
predictions of collider observables. The “leading-log” QCD Monte-Carlo model estimates
are the “base line” from which other calculations can be compared.
 I see no reason why the QCD “leading-log” Monte-Carlo models should not qualitatively
describe heavy quark production (in the same way they qualitatively describe light quark and
gluon production).
 We measure hadrons & Want
leptons
gluons) and hadronization effects are
to (NOT
know quarks
what the&“leading-log”
important! The QCD “leading-log”
Monte-Carlo
models
incorporate fragmentation via
QCD Monte-Carlo
Models
predict,
“string fragmentation” or “cluster fragmentation” or “FF fragmentation” thus producing
how stable the estimates are,
hadrons and leptons.
and how they compare with data.
 At “leading-log” order the sources of b-quarks can be divided into three categories: “flavor
creation”, “flavor excitation”, “shower/fragmentation” (i.e. “gluon splitting”).
“Flavor Creation”
“Flavor Excitation”
b-quark
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
b-quark
Proton
“Parton Shower/Fragmentation”
b-quark
AntiProton
Underlying Event
Underlying Event
b-quark
Initial-State
Radiation
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
gluon, quark,
or antiquark
b-quark
b-quark
All three sources are important at the Tevatron!
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 2
b-Quark Production
at the Tevatron
 I believe it is important to have good “leading-log” order QCD Monte-Carlo model
predictions of collider observables. The “leading-log” QCD Monte-Carlo model estimates
are the “base line” from which other calculations can be compared.
 I see no reason why the QCD “leading-log” Monte-Carlo models should not qualitatively
describe heavy quark production (in the same way they qualitatively describe light quark and
gluon production).
Soon!…
when we
haveand hadronization effects are
 We measure hadrons & Want
leptons
gluons)
to (NOT
know quarks
what the&“leading-log”
important! The QCD “leading-log”
Monte-Carlo
models
incorporate fragmentation via
beyond
“leading-log”
order
QCD
Monte-Carlo
Models
predict,
“string fragmentation” or “cluster fragmentation” or “FF fragmentation” thus producing
how
stable the estimates
are,
Monte-Carlo
models
hadrons and leptons.
and how
they
compare with data.
with
 At “leading-log” order the sources
offragmentation!
b-quarks can be divided into three categories: “flavor
creation”, “flavor excitation”, “shower/fragmentation” (i.e. “gluon splitting”).
“Flavor Creation”
“Flavor Excitation”
b-quark
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
b-quark
Proton
“Parton Shower/Fragmentation”
b-quark
AntiProton
Underlying Event
Underlying Event
b-quark
Initial-State
Radiation
Proton
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
gluon, quark,
or antiquark
b-quark
b-quark
All three sources are important at the Tevatron!
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 3
“Flavor Creation”
“Flavor Creation”
Integrated b-quark Cross Section for PT > PTmin
b-quark
1.0E+01
Proton
q or g
q or g
1.0E+00
Underlying Event
Initial-State
Radiation
b-quark
“Flavor Creation” corresponds to
the production of a b-bbar pair
by gluon fusion or by annihilation
of light quarks.
Cross Section (b)
Underlying Event
1.8 TeV
|y| < 1
AntiProton
CTEQ3L
1.0E-01
Pythia Creation
Isajet Creation
1.0E-02
Herwig Creation
D0 Data
CDF Data
Leading-Log order “Flavor
Creation” is a factor of four
below the data!
1.0E-03
5
10
15
20
25
30
35
40
PTmin (GeV/c)
 Data from CDF and D0 for the integrated b-quark total cross section (PT > PTmin, |y| < 1)
for proton-antiproton collisions at 1.8 TeV compared with the QCD Monte-Carlo model
predictions of HERWIG, PYTHIA, and ISAJET for the “flavor creation” subprocesses.
The parton distribution functions CTEQ3L have been used for all three Monte-Carlo
models. .
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 4
“Flavor Excitation”
“Gluon Splitting”
“Flavor Excitation”
“Parton Shower/Fragmentation”
b-quark
Proton
AntiProton
Underlying Event
Underlying Event
Proton
AntiProton
Underlying Event
Underlying Event
b-quark
Initial-State
Radiation
Initial-State
Radiation
gluon, quark,
or antiquark
“Flavor Excitation” corresponds to the
scattering of a b-quark (or bbar-quark) out of
the initial-state into the final-state by a gluon
or by a light quark or antiquark.
b-quark
b-quark
The b-bbar pair is created within a parton shower or during the
the fragmentation process of a gluon or a light quark or
antiquark. Here the QCD hard 2-to-2 subprocess involves
gluons and light quarks and antiquarks. This includes what is
referred to as “gluon splitting”.
 “Flavor excitation” is, of course, very sensitive to the number of b-quarks within the
proton (i.e. the structure functions).
 The Monte-Carlo models predictions for the “shower/fragmentation” contribution differ
considerably. This is not surprising since ISAJET uses independent fragmentation, while
HERWIG and PYTHIA do not; and HERWIG and PYTHIA modify the leading-log picture
of parton showers to include “color coherence effects”, while ISAJET does not.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 5
Integrated Inclusive
b-Quark Cross Section
Integrated b-quark Cross Section for PT > PTmin
Total
1.0E+02
“Flavor Excitation”
PYTHIA 6.158
CTEQ3L PARP(67)=4
PY 6.158 (67=4) Total
Flavor Creation
Flavor Excitation
1.0E+01
“Flavor Creation”
Cross Section (b)
Shower/Fragmentation
D0 Data
CDF Data
1.0E+00
1.0E-01
1.8 TeV
|y| < 1
1.0E-02
“Gluon Splitting”
1.0E-03
0
5
10
15
20
25
30
35
40
PTmin (GeV/c)
 Data on the integrated b-quark total cross section (PT > PTmin, |y| < 1) for protonantiproton collisions at 1.8 TeV compared with the QCD Monte-Carlo model predictions
of PYTHIA 6.158 (CTEQ3L, PARP(67)=4). The four curves correspond to the
contribution from “flavor creation”, “flavor excitation”, “shower/fragmentation”, and
the resulting total.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 6
Integrated Inclusive
PYTHIA
Tune A Section
b-Quark
Cross
Integrated b-quark Cross Section for PT > PTmin
Integrated b-quark Cross Section for PT > PTmin
1.0E+02
1.0E+02
PYTHIA 6.206
CTEQ5L PARP(67)=1
1.0E+00
1.0E-01
PY 6.206 (67=4) Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.0E+01
Cross Section (b)
1.0E+01
Cross Section (b)
PYTHIA 6.206
CTEQ5L PARP(67)=4
PY 6.206 (67=1) Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.0E+00
1.0E-01
1.8 TeV
|y| < 1
1.8 TeV
|y| < 1
1.0E-02
1.0E-02
Changed at version 6.138!
1.0E-03
1.0E-03
0
5
10
15
20
25
30
35
40
0
PTmin (GeV/c)

5
10
15
20
25
30
35
40
PTmin (GeV/c)
Data on the integrated b-quark total cross section (PT > PTmin, |y| < 1) for proton-antiproton collisions
at 1.8 TeV compared with the QCD Monte-Carlo model predictions of PYTHIA 6.206 (CTEQ5L) with
PARP(67)=1 (new default) and PARP(67)=4 (old default). The four curves correspond to the
contribution from flavor creation, flavor excitation, shower/fragmentation, and the resulting total.
PARP(67) is a scale factor that governs the amount of large angle initial-state radiation. Larger values of
PARP(67) results in more large angle initial-state radiation!
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 7
B+ Meson Cross Section
Integrated b-quark Cross Section for PT > PTmin
B+ Meson Transverse Momentum Distribution
1.0E+02
1.0E+01
PYTHIA 6.158
CTEQ3L PARP(67)=4
PY 6.158 (67=4) Total
Flavor Creation
PYTHIA 6.158
CTEQ3L PARP(67)=4
Flavor Excitation
1.0E+01
1.0E+00
CDF Data
ds/dPT ( b/GeV/c)
Cross Section (b)
Shower/Fragmentation
D0 Data
1.0E+00
1.0E-01
Important to compare at
the B-meson level!
1.8 TeV
|y| < 1
Total
1.0E-01
"Flavor Excitation"
1.0E-02
"Shower/Fragmentation"
1.0E-02
1.0E-03
1.8 TeV
|y| < 1
1.0E-03
"Flavor Creation"
1.0E-04
0
5
10
15
20
25
30
35
40
0
PTmin (GeV/c)
5
10
15
20
25
30
35
40
PT (GeV)
 Data on the integrated b-quark cross section (PT > PTmin, |y| < 1) at 1.8 TeV compared
with the QCD Monte-Carlo model predictions of PYTHIA 6.158 (CTEQ3L, PARP(67)=4).
 Data on the B+ meson differential cross section (|y| < 1) at 1.8 TeV compared with the
QCD Monte-Carlo model predictions of PYTHIA 6.158 (CTEQ3L, PARP(67)=4).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 8
B+ Meson Cross Section
Integrated b-quark Cross Section for PT > PTmin
B+ Meson Transverse Momentum Distribution
1.0E+02
1.0E+01
PYTHIA 6.158
CTEQ3L PARP(67)=4
PY 6.158 (67=4) Total
Flavor Creation
PYTHIA 6.158
CTEQ3L PARP(67)=4
Flavor Excitation
1.0E+01
1.0E+00
CDF Data
ds/dPT ( b/GeV/c)
Cross Section (b)
Shower/Fragmentation
D0 Data
Total
Warning!… do not use
“Peterson Fragmentation”
Important to compare
at
Use PYTHIA’s
model of
the B-meson level!
fragmentation:
“String Fragmentation”
1.0E+00
1.0E-01
1.8 TeV
|y| < 1
1.0E-01
"Flavor Excitation"
1.0E-02
"Shower/Fragmentation"
1.0E-02
1.0E-03
1.8 TeV
|y| < 1
1.0E-03
"Flavor Creation"
1.0E-04
0
5
10
15
20
25
30
35
40
0
PTmin (GeV/c)
5
10
15
20
25
30
35
40
PT (GeV)
 Data on the integrated b-quark cross section (PT > PTmin, |y| < 1) at 1.8 TeV compared
with the QCD Monte-Carlo model predictions of PYTHIA 6.158 (CTEQ3L, PARP(67)=4).
 Data on the B+ meson differential cross section (|y| < 1) at 1.8 TeV compared with the
QCD Monte-Carlo model predictions of PYTHIA 6.158 (CTEQ3L, PARP(67)=4).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 9
B+ Meson Cross Section
Integrated b-quark Cross Section for PT > PTmin
B+ Meson Transverse Momentum Distribution
1.0E+02
1.0E+01
HERWIG 6.4
CTEQ5L
HW 6.4 Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.0E+00
ds/dPT ( b/GeV/c)
Cross Section (b)
1.0E+01
HERWIG 6.4
CTEQ5L
1.0E+00
1.0E-01
Total
1.0E-01
1.0E-02
"Flavor Excitation"
"Flavor Creation"
1.8 TeV
|y| < 1
1.0E-02
1.0E-03
1.8 TeV
|y| < 1
"Shower/Fragmentation"
1.0E-03
1.0E-04
0
5
10
15
20
25
30
35
40
0
PTmin (GeV/c)
5
10
15
20
25
30
35
40
PT (GeV)
 Data on the integrated b-quark cross section (PT > PTmin, |y| < 1) at 1.8 TeV compared
with the QCD Monte-Carlo model predictions of HERWIG 6.4 (CTEQ5L).
 Data on the B+ meson differential cross section (|y| < 1) at 1.8 TeV compared with the
QCD Monte-Carlo model predictions of HERWIG 6.4 (CTEQ5L).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 10
B+ Meson Cross Section
Integrated b-quark Cross Section for PT > PTmin
B+ Meson Transverse Momentum Distribution
1.0E+02
1.0E+01
HERWIG 6.4
CTEQ5L
HW 6.4 Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.0E+00
ds/dPT ( b/GeV/c)
Cross Section (b)
1.0E+01
HERWIG 6.4
CTEQ5L
Total
Warning!… do not use
“Peterson Fragmentation”
Use HERWIG’s model of
fragmentation:
“Cluster Fragmentation”
1.0E+00
1.0E-01
1.8 TeV
|y| < 1
1.0E-02
1.0E-01
1.0E-02
"Flavor Excitation"
"Flavor Creation"
1.0E-03
1.8 TeV
|y| < 1
"Shower/Fragmentation"
1.0E-03
1.0E-04
0
5
10
15
20
25
30
35
40
0
PTmin (GeV/c)
5
10
15
20
25
30
35
40
PT (GeV)
 Data on the integrated b-quark cross section (PT > PTmin, |y| < 1) at 1.8 TeV compared
with the QCD Monte-Carlo model predictions of HERWIG 6.4 (CTEQ5L).
 Data on the B+ meson differential cross section (|y| < 1) at 1.8 TeV compared with the
QCD Monte-Carlo model predictions of HERWIG 6.4 (CTEQ5L).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 11
B+ Meson Cross Section
Integrated b-quark Cross Section for PT > PTmin
B+ Meson Transverse Momentum Distribution
1.0E+02
1.0E+01
HERWIG 6.4
CTEQ5L
HW 6.4 Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.0E+00
ds/dPT ( b/GeV/c)
Cross Section (b)
1.0E+01
HERWIG 6.4
CTEQ5L
Total
Next step is todo
study
Warning!…
not the
use
1.0E+00
1.0E-01
“Peterson
Fragmentation”
correlations
UseforHERWIG’s
model of
“Flavor Creation”,
fragmentation:
“Favor Excitation”,
“Gluon Splitting”
“Cluster
Fragmentation”
and compare
with data!
1.0E-01
1.8 TeV
|y| < 1
1.0E-02
1.0E-02
"Flavor Excitation"
"Flavor Creation"
1.0E-03
1.8 TeV
|y| < 1
"Shower/Fragmentation"
1.0E-03
1.0E-04
0
5
10
15
20
25
30
35
40
0
PTmin (GeV/c)
5
10
15
20
25
30
35
40
PT (GeV)
 Data on the integrated b-quark cross section (PT > PTmin, |y| < 1) at 1.8 TeV compared
with the QCD Monte-Carlo model predictions of HERWIG 6.4 (CTEQ5L).
 Data on the B+ meson differential cross section (|y| < 1) at 1.8 TeV compared with the
QCD Monte-Carlo model predictions of HERWIG 6.4 (CTEQ5L).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 12
PT Asymmetry
b-quark Correlations: PT Asymmetry
A=(PT1-PT2)/(PT1+PT2)
8
PT1 (b-quark)

7
Pythia CTEQ4L
1.8 TeV
PT1 > 0 GeV/c
PT2 > 5 GeV/c
|y1| < 1 |y2| < 1
ds/dA (b)
6
“Toward”
5
4
3
2
“Away”
1
0
PT2 (b-quark)
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
A=(PT1-PT2)/(PT1+PT2)
Pythia Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
 Predictions of PYTHIA 6.158 (CTEQ4L, PARP(67)=1) for the asymmetry A = (PT1PT2)/(PT1+PT2) for events with a b-quark with PT1 > 0 GeV/c and |y1| < 1.0 and a bbar
quark with PT2 > 5 GeV/c and |y2| < 1.0 in proton-antiproton collisions at 1.8 TeV. The
curves correspond to ds/dA (b) for flavor creation, flavor excitation,
shower/fragmentation, and the resulting total.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 13
Distance R in h- Space
h- Space
b-quark Correlations: Distance R
2
10.0
Pythia Total
b-quark
Pythia CTEQ4L
Flavor Creation
Flavor Excitation
ds/dR (b)
Shower/Fragmentation
R

b-quark
1.8 TeV
PT1 > 5 GeV/c
PT2 > 5 GeV/c
|y1| < 1
1.0
0.1
0
1
2
3
4
5
Distance R
0
-1
h
+1
 Predictions of PYTHIA 6.158 (CTEQ4L, PARP(67)=1) for the distance, R, in h-
space between the b and bbar-quark with PT1 > 5 GeV/c, PT2 > 5 GeV/c, and |y1|<1
in proton-antiproton collisions at 1.8 TeV. The curves correspond to ds/dR (b) for
flavor creation, flavor excitation, shower/fragmentation, and the resulting total.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 14
Distance R in h- Space
b-quark Correlations: Distance R
b-quark Correlations: Distance R
10.0
1.000
Pythia Total
Pythia CTEQ4L
Flavor Creation
Flavor Excitation
Flavor Creation
Flavor Excitation
Shower/Fragmentation
ds/dR (b)
ds/dR (b)
Shower/Fragmentation
1.0
0.1
0.100
0.010
1
2
3
4
5
0
Distance R
h- Space
+1
b-quark
R
h
b-quark
0
1.8 TeV
PT1 > 12 GeV/c
PT2 > 6 GeV/c
|y1| < 1 |y2| < 1
0.001
0
-1
Pythia CTEQ4L
Pythia Total
1.8 TeV
PT1 > 5 GeV/c
PT2 > 0 GeV/c
|y1| < 1 |y2| < 1

Fermilab MC Workshop
April 30, 2003
1
2
3
4
5
Distance R
 Predictions of PYTHIA 6.158 (CTEQ4L, PARP(67)=1)
for the distance, R, in h- space between the b and
bbar-quark with |y1|<1 and |y2|<1 in proton-antiproton
collisions at 1.8 TeV. The curves correspond to ds/dR
(b) for flavor creation, flavor excitation,
2
shower/fragmentation, and the resulting total.
Rick Field - Florida/CDF
Page 15
Azimuthal Correlations
b-quark Correlations: Azimuthal  Distribution
b-quark
direction
0.100
1.8 TeV
PT1 > 5 GeV/c
PT2 > 0 GeV/c
|y1| < 1 |y2| < 1
ds/d (b/deg)

“Toward”
Pythia CTEQ4L
0.010
“Away”
"Away"
"Toward"
bbar-quark
0.001
0
30
60
90
120
150
180
 (degrees)
Pythia Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
 Predictions of PYTHIA 6.158 (CTEQ4L, PARP(67)=1) for the azimuthal angle, ,
between a b-quark with PT1 > 5 GeV/c and |y1| < 1 and a bbar-quark with PT2 > 0
GeV/c and |y2|<1 in proton-antiproton collisions at 1.8 TeV. The curves correspond to
ds/d (b/o) for flavor creation, flavor excitation, shower/fragmentation, and the
resulting total.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 16
Azimuthal Correlations
Old PYTHIA default
(more initial-state radiation)
New PYTHIA default
(less initial-state radiation)
b-quark Correlations: Azimuthal  Distribution
b-quark Correlations: Azimuthal  Distribution
0.01000
0.01000
1.8 TeV
PT1 > 15 GeV/c
PT2 > 10 GeV/c
|y1| < 1 |y2| < 1
PYTHIA 6.206
CTEQ5L PARP(67)=1
ds/d (b/deg)
ds/d (b/deg)
1.8 TeV
PT1 > 15 GeV/c
PT2 > 10 GeV/c
|y1| < 1 |y2| < 1
0.00100
0.00010
0.00100
0.00010
"Away"
"Toward"
"Away"
"Toward"
PYTHIA 6.206
CTEQ5L PARP(67)=4
0.00001
0.00001
0
30
60
90
120
150
180
0
30
60
 (degrees)
PY62 (67=1) Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
PY62 (67=4) Total
 Predictions of PYTHIA 6.206 (CTEQ5L) with
PARP(67)=1 (new default) and PARP(67)=4 (old
default) for the azimuthal angle, , between a b-quark
with PT1 > 15 GeV/c, |y1| < 1 and bbar-quark with PT2
> 10 GeV/c, |y2|<1 in proton-antiproton collisions at 1.8
TeV. The curves correspond to ds/d (b/o) for flavor
creation, flavor excitation, shower/fragmentation, and
the resulting total.
Fermilab MC Workshop
April 30, 2003
90
120
150
180
 (degrees)
Rick Field - Florida/CDF
Flavor Creation
Flavor Excitation
Shower/Fragmentation
b-quark
direction

“Toward”
“Away”
bbar-quark
Page 17
Azimuthal Correlations“Flavor Creation”
Old PYTHIA default
(more initial-state radiation)
b-quark Correlations: Azimuthal  Distribution
b-quark Correlations: Azimuthal  Distribution
0.01000
0.010000
1.8 TeV
PT1 > 15 GeV/c
PT2 > 10 GeV/c
|y1| < 1 |y2| < 1
HERWIG 6.4
CTEQ5L
0.001000
0.00100
ds/d (b/deg)
ds/d (b/deg)
1.8 TeV
PT1 > 15 GeV/c
PT2 > 10 GeV/c
|y1| < 1 |y2| < 1
0.00010
"Flavor Creation"
CTEQ5L
HERWIG 6.4
0.000100
PYTHIA 6.206
PARP(67)=4
PYTHIA 6.206
PARP(67)=1
0.000010
"Away"
"Toward"
0.00001
"Away"
"Toward"
0
30
60
90
120
150
180
 (degrees)
HW64 Total
Flavor Creation
Flavor Excitation
0.000001
0
Shower/Fragmentation
 Predictions of HERWIG 6.4 (CTEQ5L)
for the azimuthal angle, , between a bquark with PT1 > 15 GeV/c, |y1| < 1 and
bbar-quark with PT2 > 10 GeV/c, |y2|<1
in proton-antiproton collisions at 1.8 TeV.
The curves correspond to ds/d (b/o)
for flavor creation, flavor excitation,
shower/fragmentation, and the resulting
total.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
30
60
90
120
150
180
 (degrees)
b-quark
direction
New PYTHIA default

(less initial-state radiation)
“Toward”
“Away”
bbar-quark
Page 18
Azimuthal Correlations
b-quark Correlations: Azimuthal  Distribution
b-quark Correlations: Azimuthal  Distribution
0.010000
0.010000
PYTHIA 6.206
PARP(67)=4
0.001000
PYTHIA 6.206
PARP(67)=1
1.8 TeV
PT1 > 15 GeV/c
PT2 > 10 GeV/c
|y1| < 1 |y2| < 1
"Flavor Excitation"
CTEQ5L
ds/d (b/deg)
ds/d (b/deg)
1.8 TeV
PT1 > 15 GeV/c
PT2 > 10 GeV/c
|y1| < 1 |y2| < 1
HERWIG 6.4
0.000100
"Shower/Fragmentation"
CTEQ5L
PYTHIA 6.206
PARP(67)=4
0.001000
PYTHIA 6.206
PARP(67)=1
0.000100
HERWIG 6.4
0.000010
0.000010
0
30
60
90
120
150
180
0
Predictions of PYTHIA 6.206 (CTEQ5L) with
PARP(67)=1 (new default) and PARP(67)=4 (old default)
and HERWIG 6.4 (CTEQ5L) for the azimuthal angle, ,
between a b-quark with PT1 > 15 GeV/c, |y1| < 1 and
bbar-quark with PT2 > 10 GeV/c, |y2|<1 in protonantiproton collisions at 1.8 TeV. The curves correspond to
ds/d (b/o) for flavor excitation, and
shower/fragmentation.
Fermilab MC Workshop
April 30, 2003
30
60
90
120
150
180
 (degrees)
 (degrees)

"Away"
"Toward"
"Away"
"Toward"
Rick Field - Florida/CDF
b-quark
direction

“Toward”
“Away”
bbar-quark
Page 19
CDF Run I Analysis
Azimuthal Correlations
See talk by Kevin Lannon
b-quark Correlations: Azimuthal  Distribution
at DPF2002
b-quark Correlations: Azimuthal  Distribution
0.1000
0.01000
1.8 TeV
PT1 > 15 GeV/c
PT2 > 10 GeV/c
|y1| < 1 |y2| < 1
1.8 TeV
ds/d (b/deg)
1/s ds/d (b/deg)
CDF Preliminary Data
0.0100
PYTHIA 6.206
CTEQ5L PARP(67)=4
0.00100
0.00010
0.0010
"Away"
"Toward"
"Away"
"Toward"
0.00001
0
0.0001
0
30
60
90
 (degrees)
120
150
30
60
PY62 (67=4) Total
Flavor Creation
 Run I preliminary uncorrected CDF data for the azimuthal
angle, , between a b-quark |y1| < 1 and bbar-quark |y2|<1 in
proton-antiproton collisions at 1.8 TeV.
 Warning! Can compare theory with data only after detector
simulation (this now has been done!).
Fermilab MC Workshop
April 30, 2003
90
120
150
180
 (degrees)
180
Rick Field - Florida/CDF
Flavor Excitation
Shower/Fragmentation
b-quark
direction

“Toward”
“Away”
bbar-quark
Page 20
CDF Run 1 Analysis
Azimuthal
PYTHIA Tune Correlations
A
“Gluon Splitting”!
b-quark
direction

“Toward”
“Away”
bbar-quark
See the next talk
by Kevin Lannon!
 Run 1 preliminary CDF data for the azimuthal angle, , between a b-quark |y1| < 1
and bbar-quark |y2|<1 in proton-antiproton collisions at 1.8 TeV compared with
PYTHIA Tune A after detector simulations.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 21
Pair Differential Cross Section
Pair Differential Cross Section
1.0E-01
PT1 (b-quark)

Flavor Creation
ds/dPT2 (b/GeV/c)
“Toward”
“Away”
PT2 (b-quark)
Pythia Total
Pythia CTEQ4L
Flavor Excitation
Shower/Fragmentation
1.0E-02
1.0E-03
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.0E-04
0
5
10
15
20
25
30
35
40
PT2 (GeV/c)
 Predictions of PYTHIA 6.158 (CTEQ4L, PARP(67)=1) for the transverse momentum,
PT2, of a bbar-quark with |y2| < 1.0 for events with a b-quark with PT1 > 12 GeV/c and
|y1| < 1 in proton-antiproton collisions at 1.8 TeV. The curves correspond to ds/dPT2
(b/GeV/c) for flavor creation, flavor excitation, shower/fragmentation, and the
resulting total.
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 22
“Toward” and “Away”
Pair Differential Cross Section
Pair Differential Cross Section
Pair Differential Cross Section
1.0E-01
0.04
0.01
ds/dPT2 ( b/GeV/c)
ds/dPT2 ( b/GeV/c)
1.0E-02
0.03
PYTHIA 6.206
CTEQ5L PARP(67)=1
0.02
"Away"
"Toward"
"Away"
"Toward"
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.0E-03
1.0E-04
1.0E-05
0.00
-25
1.0E-06
-20
-15
-10
-5
0
5
10
15
20
25
-40 -35 -30 -25 -20 -15 -10
PT2 (GeV/c)
“Towards”
PYTHIA 6.206
CTEQ5L PARP(67)=1
-5
0
5
10
15
20
25
30
35
40
PT2 (GeV/c)
 Predictions of PYTHIA 6.206 (CTEQ5L,
PARP(67)=1) for the transverse momentum, PT2,
of a bbar-quark with |y2| < 1.0 for events with a bquark with PT1 > 12 GeV/c and |y1| < 1 in protonantiproton collisions at 1.8 TeV. The curves
correspond to ds/dPT2 (b/GeV/c) for the
“Away”
“Away”
“toward” and “away” region of  for flavor
creation, flavor excitation, shower/fragmentation,
PT2 (b-quark)
and the resulting total.
PT1 (b-quark)

“Toward”
“Away”
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 23
“Toward” and “Away”
Pair Differential Cross Section
Pair Differential Cross Section
Pair Differential Cross Section
1.0E-01
0.07
"Away"
"Toward"
"Away"
"Toward"
0.06
ds/dPT2 ( b/GeV/c)
ds/dPT2 ( b/GeV/c)
1.0E-02
0.05
0.04
PYTHIA 6.206
CTEQ5L PARP(67)=4
0.03
0.02
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.0E-03
1.0E-04
1.0E-05
PYTHIA 6.206
CTEQ5L PARP(67)=4
0.01
0.00
-25
1.0E-06
-20
-15
-10
-5
0
5
10
15
20
25
-40 -35 -30 -25 -20 -15 -10
PT2 (GeV/c)
“Towards”
-5
0
5
10
15
20
25
30
35
40
PT2 (GeV/c)
 Predictions of PYTHIA 6.206 (CTEQ5L,
PARP(67)=4) for the transverse momentum, PT2,
of a bbar-quark with |y2| < 1.0 for events with a bquark with PT1 > 12 GeV/c and |y1| < 1 in protonantiproton collisions at 1.8 TeV. The curves
correspond to ds/dPT2 (b/GeV/c) for the
“toward” and “away” region of  for flavor
“Away”
“Away”
creation, flavor excitation, shower/fragmentation,
PT2 (b-quark)
and the resulting total.
PT1 (b-quark)

“Toward”
“Away”
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 24
“Toward” and “Away”
Pair Differential Cross Section
Pair Differential Cross Section
Pair Differential Cross Section
1.0E-01
0.04
0.03
0.01
ds/dPT2 ( b/GeV/c)
ds/dPT2 ( b/GeV/c)
1.0E-02
HERWIG 6.4
CTEQ5L
0.02
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.0E-03
1.0E-04
1.0E-05
0.00
-25
HERWIG 6.4
CTEQ5L
1.0E-06
-20
-15
-10
-5
0
5
10
15
20
25
-40 -35 -30 -25 -20 -15 -10
PT2 (GeV/c)
“Towards”
"Away"
"Toward"
"Away"
"Toward"
PT1 (b-quark)

“Toward”
“Away”
“Away”
“Away”
PT2 (b-quark)
Fermilab MC Workshop
April 30, 2003
-5
0
5
10
15
20
25
30
35
40
PT2 (GeV/c)
 Predictions of HERWIG 6.4 (CTEQ5L) for the
transverse momentum, PT2, of a bbar-quark
with |y2| < 1.0 for events with a b-quark with
PT1 > 12 GeV/c and |y1| < 1 in proton-antiproton
collisions at 1.8 TeV. The curves correspond to
ds/dPT2 (b/GeV/c) for the “toward” and
“away” region of  for flavor creation, flavor
excitation, shower/fragmentation, and the
resulting total.
Rick Field - Florida/CDF
Page 25
“Toward” and “Away”
Pair Differential Cross Section
1.0E-03
1.0E-04
1.0E-03
1.0E-04
-5
0
5
10
PT2 (GeV/c)
15
20
25
30
35
40
1.0E-03
1.0E-04
HERWIG 6.4
CTEQ5L
1.0E-06
-40 -35 -30 -25 -20 -15 -10
-5
0
5
10
15
20
25
30
35
40
-40 -35 -30 -25 -20 -15 -10
Rick Field - Florida/CDF
-5
0
5
10
15
20
25
30
35
PT2 (GeV/c)
PT2 (GeV/c)
 Predictions of PYTHIA 6.206 (CTEQ5L)
PARP(67)=1 and PARP(67)=4 and HERWIG
6.4 (CTEQ5L) for the transverse momentum,
PT2, of a bbar-quark with |y2| < 1.0 for events
with a b-quark with PT1 > 12 GeV/c and |y1| <
1 in proton-antiproton collisions at 1.8 TeV.
The curves correspond to ds/dPT2 (b/GeV/c)
for the “toward” and “away” region of  for
flavor creation, flavor excitation,
shower/fragmentation, and the resulting total.
Fermilab MC Workshop
April 30, 2003
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.0E-05
PYTHIA 6.206
CTEQ5L PARP(67)=4
1.0E-06
1.0E-06
-40 -35 -30 -25 -20 -15 -10
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.0E-05
PYTHIA 6.206
CTEQ5L PARP(67)=1
"Away"
"Toward"
1.0E-02
ds/dPT2 (b/GeV/c)
1.0E-02
1.8 TeV
PT1 > 12 GeV/c
|y1| < 1 |Y2| < 1
1.0E-05
"Away"
"Toward"
ds/dPT2 (b/GeV/c)
ds/dPT2 (b/GeV/c)
1.0E-02
1.0E-01
1.0E-01
"Away"
"Toward"
Pair Differential Cross Section
Pair Differential Cross Section
Pair Differential Cross Section
1.0E-01
PT1 (b-quark)

“Toward”
“Away”
PT2 (b-quark)
Page 26
40
Integrated Pair Cross Section
HERWIG a factor of
two below data.
Integrated Pair Cross Section for PT2 > PT2min
Integrated Pair Cross Section for PT2 > PT2min
1.0E+02
1.0E+02
Flavor Creation
Flavor Excitation
1.0E+01
CDF Data
1.0E+00
1 = b-quark
2 = bbar-quark
PT1 > 6.5 GeV/c
PT2 > PT2min
|y1| < 1 |y2| < 1
1.0E-01
Pythia 6.206 (67=4) Total
Flavor Creation
Flavor Excitation
1.0E+01
Fragmentation
Cross Section (b)
Cross Section (b)
PYTHIA 6.206
1.8 TeV CTEQ5L
PARP(67)=4
HERWIG 6.4 Total
HERWIG 6.4
1.8 TeV CTEQ5L
Shower/Fragmentation
CDF Data
1.0E+00
1 = b-quark
2 = bbar-quark
PT1 > 6.5 GeV/c
PT2 > PT2min
|y1| < 1 |y2| < 1
1.0E-01
1.0E-02
1.0E-02
0
5
10
15
20
0
PT2min (GeV/c)
PT1 (b-quark)

PT2 (b-quark)
Fermilab MC Workshop
April 30, 2003
10
15
20
PT2min (GeV/c)

Predictions of PYTHIA 6.206 (CTEQ5L, PARP(67)=4) and HERWIG 6.4
(CTEQ5L) for the intrgrated pair cross section for a bbar-quark with PT2 >
PT2min, |y2| < 1.0 for events with a b-quark with PT1 > 6.5 GeV/c, |y1| < 1 in
proton-antiproton collisions at 1.8 TeV. The curves correspond to s(b) for
flavor creation, flavor excitation, shower/fragmentation, and the resulting
total.

Important to see the data at the meson level as well as the quark level and
both separated into the “toward” and “away” region!
“Toward”
“Away”
5
Rick Field - Florida/CDF
Page 27
Summary & Conclusions
“Flavor Creation”
Proton
“Flavor Excitation”
b-quark
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
b-quark
“Parton Shower/Fragmentation”
b-quark
Proton
AntiProton
Underlying Event
Underlying Event
Proton
AntiProton
Underlying Event
Underlying Event
b-quark
Initial-State
Radiation
Initial-State
Radiation
All three sources are important at the Tevatron!
gluon, quark,
or antiquark
b-quark
b-quark




The QCD “leading-log” Monte-Carlo models do a fairly good qualitative job in describing the b-quark
data at the Tevatron. The QCD “leading-log” Monte-Carlo models do a much better job fitting the bquark data than most people realize!
Much more Run 2 CDF data is on the way! In particular, we should be able experimentally to isolate
the individual contributions to b-quark production by studying b-bbar correlations and we will find out
in much greater detail how well the QCD Monte-Carlo models actually describe the data.
Personal Remark: I do not like it when the experimenters extrapolate to the parton level and publish
parton level results. The parton level is not an observable! Experiments measure hadrons & leptons!
To extrapolate to the parton level requires making additional assumptions that may or may not be
correct (and often the assumptions are not clearly stated or are very complicated). However, I understand
why this happens (and I cannot stop it) so I suggest that the experimenters always publish the
corresponding hadron level result along with their parton level extrapolations.
Personal Remark: I do not like it when theorists attempt to compare parton level calculations with
experimental data. Hadronization and initial/final-state radiation effects are almost always important
and hence parton level calculations should be embedded within a parton-shower/hadronization
framework (e.g. HERWIG or PYTHIA).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 28
Summary & Conclusions
“Flavor Creation”
Proton
“Flavor Excitation”
b-quark
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
b-quark
“Parton Shower/Fragmentation”
b-quark
Proton
AntiProton
Underlying Event
Underlying Event
Proton
AntiProton
Underlying Event
Underlying Event
b-quark
Initial-State
Radiation
Initial-State
Radiation
All three sources are important at the Tevatron!
gluon, quark,
or antiquark
b-quark
b-quark




The QCD “leading-log” Monte-Carlo models do a fairly good qualitative job in describing the b-quark
data at the Tevatron. The QCD “leading-log” Monte-Carlo models do a much better job fitting the bquark data than most people realize!
I am
trying be
to able experimentally to isolate
Much more Run 2 CDF data is on the way! In particular, we
should
influence
CDF!correlations and we will find out
the individual contributions to b-quark production by studying
b-bbar
in much greater detail how well the QCD Monte-Carlo models actually describe the data.This is now finally
being
done!
Personal Remark: I do not like it when the experimenters extrapolate to the parton level and
publish
parton level results. The parton level is not an observable! Experiments measure hadrons & leptons!
To extrapolate to the parton level requires making additional assumptions that may or may not be
correct (and often the assumptions are not clearly stated or are very complicated). However, I understand
why this happens (and I cannot stop it) so I suggest that the experimenters always publish the
corresponding hadron level result along with their parton level extrapolations.
Personal Remark: I do not like it when theorists attempt to compare parton level calculations with
experimental data. Hadronization and initial/final-state radiation effects are almost always important
and hence parton level calculations should be embedded within a parton-shower/hadronization
framework (e.g. HERWIG or PYTHIA).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 29
Summary & Conclusions
“Flavor Creation”
Proton
“Flavor Excitation”
b-quark
AntiProton
Underlying Event
Underlying Event
Initial-State
Radiation
b-quark
“Parton Shower/Fragmentation”
b-quark
Proton
AntiProton
Underlying Event
Underlying Event
Proton
AntiProton
Underlying Event
Underlying Event
b-quark
Initial-State
Radiation
Initial-State
Radiation
All three sources are important at the Tevatron!
gluon, quark,
or antiquark
b-quark
b-quark




The QCD “leading-log” Monte-Carlo models
do a fairly
The next
stepgood
is qualitative job in describing the b-quark
data at the Tevatron. The QCD “leading-log” Monte-Carlo models do a much better job fitting the bquark data than most people realize! to compare with
I am
trying be
to able experimentally to isolate
Much more Run 2 CDF data is on next-to-leading
the way! In particular,order
we
should
influence
CDF!correlations and we will find out
the individual contributions to b-quark production by studying
b-bbar
embedded
within
in much greater detail how well the QCD Monte-Carlo models actually describe the data.This is now finally
being
done!
or PYTHIA!
Personal Remark: I do not like HERWIG
it when the experimenters
extrapolate to the parton level and
publish
parton level results. The parton level is not an observable! Experiments measure hadrons & leptons!
To extrapolate to the parton level requires making additional assumptions that may or may not be
correct (and often the assumptions are not clearly stated or are very complicated). However, I understand
why this happens (and I cannot stop it) so I suggest that the experimenters always publish the
corresponding hadron level result along with their parton level extrapolations.
Personal Remark: I do not like it when theorists attempt to compare parton level calculations with
experimental data. Hadronization and initial/final-state radiation effects are almost always important
and hence parton level calculations should be embedded within a parton-shower/hadronization
framework (e.g. HERWIG or PYTHIA).
Fermilab MC Workshop
April 30, 2003
Rick Field - Florida/CDF
Page 30