Cambridge Workshop July 18, 2002 Rick Field - Florida/CDFPage 1 The Sources of b-Quarks at the...
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Transcript of Cambridge Workshop July 18, 2002 Rick Field - Florida/CDFPage 1 The Sources of b-Quarks at the...
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 1
The Sources of b-QuarksThe Sources of b-Quarksat the Tevatronat the Tevatron
Important to have good leading (or 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 all other calculations can be compared.
If the leading-log order estimates are within a factor of two of the data, higher order calculations might be expected to improve the agreement.
If a leading-log order estimate is off by more than a factor of two, it usually means that one has overlooked something.
I see no reason why the QCD Monte-Carlo models should not qualitatively describe heavy quark production (in the same way they qualitatively describe light quark and gluon production).
Integrated b-quark Cross Section for PT > PTmin
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
5 10 15 20 25 30 35 40
PTmin (GeV/c)
Cro
ss
Se
cti
on
(b
)
Pythia Creation
Isajet Creation
Herwig Creation
D0 Data
CDF Data
1.8 TeV|y| < 1
CTEQ3L
QCD Monte-Carlo leading order “Flavor Creation” is a factor of four below the data! “Something is goofy” (Rick Field, CDF B
Group Talk, December 3, 1999).
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 2
““Flavor Creation”Flavor Creation”
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. .
Integrated b-quark Cross Section for PT > PTmin
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
5 10 15 20 25 30 35 40
PTmin (GeV/c)C
ros
s S
ec
tio
n (
b)
Pythia Creation
Isajet Creation
Herwig Creation
D0 Data
CDF Data
1.8 TeV|y| < 1
CTEQ3L
Leading-Log order “Flavor Creation” is a factor of four below the data!
Proton AntiProton
“Flavor Creation”
Proton AntiProton
“Flavor Creation” b-quark
b-quark
Underlying Event Underlying Event
Initial-State Radiation
gluon
2-to-2 Hard Scattering Subprocesses b-quark b-quark
q q gluon gluon
gluon
b-quark b-quark
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 3
Other Sources of b-QuarksOther Sources of b-Quarks
“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.
“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.
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”.
Proton AntiProton
“Flavor Excitation” b-quark
gluon, quark, or antiquark
b-quark
Proton AntiProton
“Parton Shower/Fragmentation”
b-quark
Underlying Event Underlying Event
Initial-State Radiation
b-quark
Proton AntiProton
“Flavor Excitation” b-quark
gluon, quark, or antiquark
Underlying Event Underlying Event
Initial-State Radiation
b-quark
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 4
Integrated b-quark Cross Section for PT > PTmin
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1.0E+02
0 5 10 15 20 25 30 35 40
PTmin (GeV/c)
Cro
ss
Se
cti
on
( b
)
PY 6.158 (67=4) Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.8 TeV|y| < 1
PYTHIA 6.158CTEQ3L PARP(67)=4
Inclusive b-quark Inclusive b-quark Cross SectionCross Section
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 6.158 (CTEQ3L, PARP(67)=4). The four curves correspond to the contribution from “flavor creation”, “flavor excitation”, “shower/fragmentation”, and the resulting total.
Total
“Flavor Creation”
“Flavor Excitation”
“Shower/Fragmentation”
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 5
Inclusive b-quark Cross SectionInclusive b-quark Cross Section
Integrated b-quark Cross Section for PT > PTmin
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1.0E+02
0 5 10 15 20 25 30 35 40
PTmin (GeV/c)
Cro
ss S
ecti
on
( b
)
PY 6.206 (67=1) Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.8 TeV|y| < 1
PYTHIA 6.206CTEQ5L PARP(67)=1
Integrated b-quark Cross Section for PT > PTmin
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1.0E+02
0 5 10 15 20 25 30 35 40
PTmin (GeV/c)
Cro
ss S
ecti
on
( b
)
PY 6.206 (67=4) Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.8 TeV|y| < 1
PYTHIA 6.206CTEQ5L PARP(67)=4
Changed at version 6.138!
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!
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 6
Inclusive b-quark and BInclusive b-quark and B++ Meson Meson Cross SectionCross Section
Data on the integrated b-quark total and B+ meson cross section (PT > PTmin, |y| < 1) for proton-antiproton collisions at 1.8 TeV compared with the QCD Monte-Carlo model predictions of PYTHIA 6.158 (CTEQ3L, PARP(67)=4). The four curves correspond to the contribution from flavor creation, flavor excitation, shower/fragmentation, and the resulting total.
B+ Meson Transverse Momentum Distribution
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
0 5 10 15 20 25 30 35 40
PT (GeV)
ds /
dP
T ( b
/GeV
/c)
1.8 TeV|y| < 1
PYTHIA 6.158CTEQ3L PARP(67)=4
Total
"Flavor Excitation"
"Flavor Creation"
"Shower/Fragmentation"
Integrated b-quark Cross Section for PT > PTmin
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1.0E+02
0 5 10 15 20 25 30 35 40
PTmin (GeV/c)
Cro
ss S
ecti
on
( b
)
PY 6.158 (67=4) Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.8 TeV|y| < 1
PYTHIA 6.158CTEQ3L PARP(67)=4
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 7
Inclusive b-quark and BInclusive b-quark and B++ Meson Meson Cross SectionCross Section
Data on the integrated b-quark and B+ meson 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 6.4 (CTEQ5L). The four curves correspond to the contribution from flavor creation, flavor excitation, shower/fragmentation, and the resulting total.
Integrated b-quark Cross Section for PT > PTmin
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1.0E+02
0 5 10 15 20 25 30 35 40
PTmin (GeV/c)
Cro
ss S
ecti
on
( b
)
HW 6.4 Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
D0 Data
CDF Data
1.8 TeV|y| < 1
HERWIG 6.4CTEQ5L
B+ Meson Transverse Momentum Distribution
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
0 5 10 15 20 25 30 35 40
PT (GeV)
ds /
dP
T ( b
/GeV
/c)
1.8 TeV|y| < 1
HERWIG 6.4CTEQ5L
Total
"Flavor Excitation""Flavor Creation"
"Shower/Fragmentation"
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 8
All three sources are important at the Tevatron!
Preliminary ConclusionsPreliminary Conclusions
One should not take the QCD Monte-Carlo model estimates of “flavor excitation” and “shower/fragmentation” too seriously. The contributions from these subprocesses are qualitative estimates and more work needs to be done. There are many subtleties!
Clearly all three sources are important at the Tevatron. “Nothing is goofy” (Rick Field, CDF B Group Talk, March 9, 2001). Next step is to study in detail b-bbar correlations and the compare the predictions of
HERWIG, ISAJET, and PYTHIA in order to understand how reliable the estimates are. Want to know what the leading-log QCD Monte-Carlo Models predict, how stable the
estimates are, and how they compare with data. Also, if it is possible we would like to tune the Monte-Carlo models to fit the data.
Proton AntiProton
“Flavor Excitation” b-quark
gluon, quark, or antiquark
Underlying Event Underlying Event
Initial-State Radiation
b-quark
Proton AntiProton
“Parton Shower/Fragmentation”
b-quark
Underlying Event Underlying Event
Initial-State Radiation
b-quark
Proton AntiProton
“Flavor Creation” b-quark
b-quark
Underlying Event Underlying Event
Initial-State Radiation
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 9
PT AsymmetryPT Asymmetry
Predictions of PYTHIA 6.158 (CTEQ4L, PARP(67)=1) for the asymmetry A = (PT1-PT2)/(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.
PT1 (b-quark)
“Toward”
“Away”
PT2 (b-quark)
A=(PT1-PT2)/(PT1+PT2) b-quark Correlations: PT Asymmetry
0
1
2
3
4
5
6
7
8
-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)
ds /
dA
( b
)
Pythia Total Flavor Creation Flavor Excitation Shower/Fragmentation
1.8 TeVPT1 > 0 GeV/cPT2 > 5 GeV/c
|y1| < 1 |y2| < 1
Pythia CTEQ4L
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 10
Distance R in Distance R in -- Space Space
Predictions of PYTHIA 6.158 (CTEQ4L, PARP(67)=1) for the distance, R, in - 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.
b-quark Correlations: Distance R
0.1
1.0
10.0
0 1 2 3 4 5
Distance R
ds /
dR
( b
)
Pythia Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
1.8 TeVPT1 > 5 GeV/cPT2 > 5 GeV/c
|y1| < 1
Pythia CTEQ4L
-1 +1
2
0
b-quark
b-quark
R
- Space
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 11
Distance R in Distance R in -- Space Space
Predictions of PYTHIA 6.158 (CTEQ4L, PARP(67)=1) for the distance, R, in - 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, shower/fragmentation, and the resulting total.
b-quark Correlations: Distance R
0.1
1.0
10.0
0 1 2 3 4 5
Distance R
ds /
dR
( b
)
Pythia Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
1.8 TeVPT1 > 5 GeV/cPT2 > 0 GeV/c|y1| < 1 |y2| < 1
Pythia CTEQ4L
b-quark Correlations: Distance R
0.001
0.010
0.100
1.000
0 1 2 3 4 5
Distance R
ds /
dR
( b
)
Pythia Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
1.8 TeVPT1 > 12 GeV/cPT2 > 6 GeV/c|y1| < 1 |y2| < 1
Pythia CTEQ4L
-1
+1
2 0
R
- Space
b-quark
b-quark
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 12
Azimuthal CorrelationsAzimuthal Correlations
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.
b-quark direction
“Toward”
“Away”
bbar-quark
b-quark Correlations: Azimuthal Distribution
0.001
0.010
0.100
0 30 60 90 120 150 180
(degrees)
ds /
d
(b
/deg
)
Pythia Total Flavor Creation Flavor Excitation Shower/Fragmentation
1.8 TeVPT1 > 5 GeV/cPT2 > 0 GeV/c
|y1| < 1 |y2| < 1
"Away""Toward"
Pythia CTEQ4L
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 13
Azimuthal CorrelationsAzimuthal Correlations
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.
b-quark Correlations: Azimuthal Distribution
0.00001
0.00010
0.00100
0.01000
0 30 60 90 120 150 180
(degrees)
ds /
d
(b
/deg
)
PY62 (67=1) Total Flavor Creation Flavor Excitation Shower/Fragmentation
1.8 TeVPT1 > 15 GeV/cPT2 > 10 GeV/c|y1| < 1 |y2| < 1
PYTHIA 6.206 CTEQ5L PARP(67)=1
"Away""Toward"
b-quark direction
“Toward”
“Away”
bbar-quark
b-quark Correlations: Azimuthal Distribution
0.00001
0.00010
0.00100
0.01000
0 30 60 90 120 150 180
(degrees)
ds /
d
(b
/de
g)
PY62 (67=4) Total Flavor Creation Flavor Excitation Shower/Fragmentation
1.8 TeVPT1 > 15 GeV/cPT2 > 10 GeV/c|y1| < 1 |y2| < 1
PYTHIA 6.206 CTEQ5L PARP(67)=4
"Away""Toward"
New PYTHIA default(less initial-state radiation)
Old PYTHIA default(more initial-state radiation)
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 14
Azimuthal CorrelationsAzimuthal Correlations
Predictions of 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 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.
b-quark Correlations: Azimuthal Distribution
0.00001
0.00010
0.00100
0.01000
0 30 60 90 120 150 180
(degrees)
ds /
d
(b
/de
g)
HW64 Total Flavor Creation Flavor Excitation Shower/Fragmentation
1.8 TeVPT1 > 15 GeV/cPT2 > 10 GeV/c|y1| < 1 |y2| < 1
HERWIG 6.4 CTEQ5L
"Away""Toward"
b-quark direction
“Toward”
“Away”
bbar-quark
b-quark Correlations: Azimuthal Distribution
0.000001
0.000010
0.000100
0.001000
0.010000
0 30 60 90 120 150 180
(degrees)
ds /
d
(b
/deg
)
1.8 TeVPT1 > 15 GeV/cPT2 > 10 GeV/c|y1| < 1 |y2| < 1
"Flavor Creation" CTEQ5L
"Away""Toward"
HERWIG 6.4
PYTHIA 6.206PARP(67)=1
PYTHIA 6.206PARP(67)=4
“Flavor Creation”
New PYTHIA default(less initial-state radiation)
Old PYTHIA default(more initial-state radiation)
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 15
Azimuthal CorrelationsAzimuthal Correlations
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 proton-antiproton collisions at 1.8 TeV. The curves correspond to ds/d (b/o) for flavor excitation, and shower/fragmentation.
b-quark Correlations: Azimuthal Distribution
0.000010
0.000100
0.001000
0.010000
0 30 60 90 120 150 180
(degrees)
ds /
d
(b
/deg
)
1.8 TeVPT1 > 15 GeV/cPT2 > 10 GeV/c|y1| < 1 |y2| < 1
"Flavor Excitation" CTEQ5L
"Away""Toward"
PYTHIA 6.206PARP(67)=1
HERWIG 6.4
PYTHIA 6.206PARP(67)=4
b-quark direction
“Toward”
“Away”
bbar-quark
b-quark Correlations: Azimuthal Distribution
0.000010
0.000100
0.001000
0.010000
0 30 60 90 120 150 180
(degrees)
ds /
d
(b
/deg
)
1.8 TeVPT1 > 15 GeV/cPT2 > 10 GeV/c|y1| < 1 |y2| < 1
"Shower/Fragmentation"CTEQ5L
"Away""Toward"
PYTHIA 6.206PARP(67)=4
HERWIG 6.4
PYTHIA 6.206PARP(67)=1
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 16
CDF Run I AnalysisCDF Run I AnalysisAzimuthal CorrelationsAzimuthal Correlations
New 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.
b-quark direction
“Toward”
“Away”
bbar-quark
b-quark Correlations: Azimuthal Distribution
0.0001
0.0010
0.0100
0.1000
0 30 60 90 120 150 180
(degrees)
1/s
ds /
d
(b
/de
g)
CDF Preliminary Data 1.8 TeV
"Away""Toward"
b-quark Correlations: Azimuthal Distribution
0.00001
0.00010
0.00100
0.01000
0 30 60 90 120 150 180
(degrees)
ds /
d
(b
/de
g)
PY62 (67=4) Total Flavor Creation Flavor Excitation Shower/Fragmentation
1.8 TeVPT1 > 15 GeV/cPT2 > 10 GeV/c|y1| < 1 |y2| < 1
PYTHIA 6.206 CTEQ5L PARP(67)=4
"Away""Toward"
Warning! Can compare theory with data only after detector simulation (this is being done).
Only a naïve theorist (like me!) would compare at this stage.
See talk by Kevin Lannonat DPF2002
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 17
DiPhoton CorrelationsDiPhoton Correlations
Predictions of PYTHIA 6.158 (CTEQ5L) with PARP(67)=1 (new default) and PARP(67)=4 (old default) for diphoton system PT and the azimuthal angle, , between a photon with PT1 > 12 GeV/c, |y1| < 0.9 and photon with PT2 > 12 GeV/c, |y2|< 0.9 in proton-antiproton collisions at 1.8 TeV compared with CDF data.
DiPhoton Correlations: Azimuthal Distribution
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
90 105 120 135 150 165 180
(degrees)
1/s
ds /
d
(1/d
eg
)
PYC5 DiPhoton PARP(67)=4
PYC5 DiPhoton PARP(67)=1
CDF DiPhoton Data
1.8 TeV PT > 12 GeV || < 0.9
New Pythia
Old Pythia
Diphoton System Transverse Momentum
0.00
0.05
0.10
0.15
0.20
0.25
0 2 4 6 8 10 12 14 16 18
Diphoton System PT (GeV/c)
1/s
ds /
dP
T (
1/G
eV
/c)
PYC5 DiPhoton PARP(67)=1
PYC5 DiPhoton PARP(67)=4
CDF DiPhoton Data
1.8 TeV PT > 12 GeV || < 0.9New Pythia
Old Pythia
Photon direction
“Toward”
“Away”
Photon
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 18
DiPhoton vs “Flavor Creation”DiPhoton vs “Flavor Creation”Azimuthal CorrelationsAzimuthal Correlations
Predictions of PYTHIA 6.158 (CTEQ5L) with PARP(67)=1 (new default) and PARP(67)=4 (old default) for diphoton production and b-bbar “flavor creation”.
Correlations: Azimuthal Distribution
0.0001
0.0010
0.0100
0.1000
1.0000
0 30 60 90 120 150 180
(degrees)
1/s
ds /
d
(b
/de
g)
Pythia b-bbar Creation (67=1)
PYC5 DiPhoton PARP(67)=1
CDF DiPhoton Data
b-bbar"Flavor Creation"
DiPhotonPARP(67)=1 (new default)
Correlations: Azimuthal Distribution
0.0001
0.0010
0.0100
0.1000
1.0000
0 30 60 90 120 150 180
(degrees)
1/s
ds /
d
(b
/de
g)
Pythia b-bbar Creation (67=4)
PYC5 DiPhoton PARP(67)=4
CDF DiPhoton Data
b-bbar"Flavor Creation"
DiPhoton
PARP(67)=4 (old default)
Photon direction
“Toward”
“Away”
Photon
b-quark direction
“Toward”
“Away”
bbar-quark
Compare
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 19
Pair Differential Cross SectionPair Differential Cross Section
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.
PT1 (b-quark)
“Toward”
“Away”
PT2 (b-quark)
Pair Differential Cross Section
1.0E-04
1.0E-03
1.0E-02
1.0E-01
0 5 10 15 20 25 30 35 40
PT2 (GeV/c)
ds /
dP
T2
(b
/GeV
/c)
Pythia Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
Pythia CTEQ4L
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 20
““Toward” and “Away”Toward” and “Away”Pair Differential Cross SectionPair Differential Cross Section
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 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.
Pair Differential Cross Section
0.00
0.01
0.02
0.03
0.04
-25 -20 -15 -10 -5 0 5 10 15 20 25
PT2 (GeV/c)
ds /
dP
T2
( b
/Ge
V/c
)
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
PYTHIA 6.206CTEQ5L PARP(67)=1
"Away""Toward"
Pair Differential Cross Section
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40
PT2 (GeV/c)
ds /
dP
T2
( b
/Ge
V/c
)
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
PYTHIA 6.206CTEQ5L PARP(67)=1
"Away""Toward"
PT1 (b-quark)
“Toward”
“Away”
PT2 (b-quark)
“Towards”“Towards”
“Away”“Away”
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 21
““Toward” and “Away”Toward” and “Away”Pair Differential Cross SectionPair Differential Cross Section
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 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.
Pair Differential Cross Section
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
-25 -20 -15 -10 -5 0 5 10 15 20 25
PT2 (GeV/c)
ds /
dP
T2
( b
/Ge
V/c
)
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
PYTHIA 6.206CTEQ5L PARP(67)=4
"Away""Toward"
Pair Differential Cross Section
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40
PT2 (GeV/c)
ds /
dP
T2
( b
/Ge
V/c
)
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
PYTHIA 6.206CTEQ5L PARP(67)=4
"Away""Toward"
PT1 (b-quark)
“Toward”
“Away”
PT2 (b-quark)
“Towards”“Towards”
“Away”“Away”
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 22
““Toward” and “Away” Toward” and “Away” Pair Differential Cross SectionPair Differential Cross Section
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.
Pair Differential Cross Section
0.00
0.01
0.02
0.03
0.04
-25 -20 -15 -10 -5 0 5 10 15 20 25
PT2 (GeV/c)
ds /
dP
T2
( b
/Ge
V/c
)
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
HERWIG 6.4CTEQ5L
"Away""Toward"
PT1 (b-quark)
“Toward”
“Away”
PT2 (b-quark)
Pair Differential Cross Section
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40
PT2 (GeV/c)
ds /
dP
T2
( b
/Ge
V/c
)
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
HERWIG 6.4CTEQ5L
"Away""Toward"
“Towards”“Towards”
“Away”“Away”
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 23
““Toward” and “Away”Toward” and “Away”Pair Differential Cross SectionPair Differential Cross Section
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.
Pair Differential Cross Section
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40
PT2 (GeV/c)
ds /
dP
T2
( b
/Ge
V/c
)
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
PYTHIA 6.206CTEQ5L PARP(67)=1
"Away""Toward"
PT1 (b-quark)
“Toward”
“Away”
PT2 (b-quark)
Pair Differential Cross Section
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40
PT2 (GeV/c)
ds /
dP
T2
( b
/Ge
V/c
)
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
PYTHIA 6.206CTEQ5L PARP(67)=4
"Away""Toward"
Pair Differential Cross Section
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40
PT2 (GeV/c)
ds /
dP
T2
( b
/Ge
V/c
)
1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1
HERWIG 6.4CTEQ5L
"Away""Toward"
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 24
Integrated Pair Cross SectionIntegrated Pair Cross Section
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.
Integrated Pair Cross Section for PT2 > PT2min
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1.0E+02
0 5 10 15 20
PT2min (GeV/c)
Cro
ss
Se
cti
on
( b
)
HERWIG 6.4 Total
Flavor Creation
Flavor Excitation
Fragmentation
CDF Data
HERWIG 6.41.8 TeV CTEQ5L
1 = b-quark2 = bbar-quark
PT1 > 6.5 GeV/cPT2 > PT2min|y1| < 1 |y2| < 1
Integrated Pair Cross Section for PT2 > PT2min
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1.0E+02
0 5 10 15 20
PT2min (GeV/c)
Cro
ss
Se
cti
on
( b
)
Pythia 6.206 (67=4) Total
Flavor Creation
Flavor Excitation
Shower/Fragmentation
CDF Data
PYTHIA 6.2061.8 TeV CTEQ5L
PARP(67)=4
1 = b-quark2 = bbar-quark
PT1 > 6.5 GeV/cPT2 > PT2min|y1| < 1 |y2| < 1
PT1 (b-quark)
“Toward”
“Away”
PT2 (b-quark)
Important to see the data at the meson level as well as the quark level and both separated into the “toward” and “away” region!
HERWIG a factor of two below data.
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 25
All three sources are important at the Tevatron!
Summary & ConclusionsSummary & Conclusions
The QCD leading-log Monte-Carlo models do a fairly good job in describing the majority of the b-quark data at the Tevatron. The QCD Monte-Carlo models do a much better job fitting the b data than most people realize!
Much more Run II (and Run I) 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! 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 extrapolation.
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 theorists should embed their parton level results within a parton-shower/hadronization framework (e.g. HERWIG or PYTHIA).
Proton AntiProton
“Flavor Excitation” b-quark
gluon, quark, or antiquark
Underlying Event Underlying Event
Initial-State Radiation
b-quark
Proton AntiProton
“Parton Shower/Fragmentation”
b-quark
Underlying Event Underlying Event
Initial-State Radiation
b-quark
Proton AntiProton
“Flavor Creation” b-quark
b-quark
Underlying Event Underlying Event
Initial-State Radiation
Cambridge Workshop July 18, 2002
Rick Field - Florida/CDF Page 26
All three sources are important at the Tevatron!
Summary & ConclusionsSummary & Conclusions
The QCD leading-log Monte-Carlo models do a fairly good job in describing the majority of the b-quark data at the Tevatron. The QCD Monte-Carlo models do a much better job fitting the b data than most people realize!
Much more Run II (and Run I) 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! 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 extrapolation.
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 theorists should embed their parton level results within a parton-shower/hadronization framework (e.g. HERWIG or PYTHIA).
Proton AntiProton
“Flavor Excitation” b-quark
gluon, quark, or antiquark
Underlying Event Underlying Event
Initial-State Radiation
b-quark
Proton AntiProton
“Parton Shower/Fragmentation”
b-quark
Underlying Event Underlying Event
Initial-State Radiation
b-quark
Proton AntiProton
“Flavor Creation” b-quark
b-quark
Underlying Event Underlying Event
Initial-State Radiation
“Nothing is goofy” Rick Field, Cambridge Workshop,
July 18, 2002