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

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).



““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. .


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



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



b-quark

Proton AntiProton





b-quark




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 Excitation”

“Shower/Fragmentation”



Inclusive b-quark Cross SectionInclusive b-quark Cross Section


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


D0 Data

CDF Data

1.8 TeV|y| < 1



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


D0 Data

CDF Data

1.8 TeV|y| < 1


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!



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


Total

"Flavor Excitation"

"Flavor Creation"

"Shower/Fragmentation"


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


D0 Data

CDF Data

1.8 TeV|y| < 1




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.


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


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"



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





b-quark

Proton AntiProton


b-quark



b-quark

Proton AntiProton


b-quark





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



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



|y1| < 1

Pythia CTEQ4L

-1 +1

2

0

b-quark

b-quark

R

- Space



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.


0.1

1.0

10.0

0 1 2 3 4 5

Distance R

ds /

dR

( b

)

Pythia Total

Flavor Creation

Flavor Excitation


1.8 TeVPT1 > 5 GeV/cPT2 > 0 GeV/c|y1| < 1 |y2| < 1

Pythia CTEQ4L


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



Pythia CTEQ4L

-1

+1

2 0

R

- Space

b-quark

b-quark



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


|y1| < 1 |y2| < 1

"Away""Toward"

Pythia CTEQ4L




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.


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


PYTHIA 6.206 CTEQ5L PARP(67)=1

"Away""Toward"

b-quark direction

“Toward”

“Away”

bbar-quark


0.00001

0.00010

0.00100

0.01000

0 30 60 90 120 150 180

(degrees)

ds /

d

(b

/de

g)




"Away""Toward"

New PYTHIA default(less initial-state radiation)

Old PYTHIA default(more initial-state radiation)




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.


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


HERWIG 6.4 CTEQ5L

"Away""Toward"

b-quark direction

“Toward”

“Away”

bbar-quark


0.000001

0.000010

0.000100

0.001000

0.010000

0 30 60 90 120 150 180

(degrees)

ds /

d

(b

/deg

)


"Flavor Creation" CTEQ5L

"Away""Toward"

HERWIG 6.4

PYTHIA 6.206PARP(67)=1



New PYTHIA default(less initial-state radiation)

Old PYTHIA default(more initial-state radiation)




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.


0.000010

0.000100

0.001000

0.010000

0 30 60 90 120 150 180

(degrees)

ds /

d

(b

/deg

)


"Flavor Excitation" CTEQ5L

"Away""Toward"


HERWIG 6.4


b-quark direction

“Toward”

“Away”

bbar-quark


0.000010

0.000100

0.001000

0.010000

0 30 60 90 120 150 180

(degrees)

ds /

d

(b

/deg

)


"Shower/Fragmentation"CTEQ5L

"Away""Toward"


HERWIG 6.4




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


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"


0.00001

0.00010

0.00100

0.01000

0 30 60 90 120 150 180

(degrees)

ds /

d

(b

/de

g)




"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



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


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)



CDF DiPhoton Data

1.8 TeV PT > 12 GeV || < 0.9New Pythia

Old Pythia

Photon direction

“Toward”

“Away”

Photon



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)


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)


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



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


Pythia CTEQ4L

1.8 TeVPT1 > 12 GeV/c|y1| < 1 |Y2| < 1



““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.


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


"Away""Toward"


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


"Away""Toward"

PT1 (b-quark)

“Toward”

“Away”

PT2 (b-quark)

“Towards”“Towards”

“Away”“Away”




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.


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


"Away""Toward"


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


"Away""Toward"

PT1 (b-quark)

“Toward”

“Away”

PT2 (b-quark)





““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.


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)


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"






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.


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


"Away""Toward"

PT1 (b-quark)

“Toward”

“Away”

PT2 (b-quark)


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


"Away""Toward"


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"



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


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.




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





b-quark

Proton AntiProton


b-quark



b-quark

Proton AntiProton


b-quark






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





b-quark

Proton AntiProton


b-quark



b-quark

Proton AntiProton


b-quark



“Nothing is goofy” Rick Field, Cambridge Workshop,

July 18, 2002

cambridge workshop july 18, 2002 rick field - florida/cdfpage 1 the sources of b-quarks at the...

Documents

qcd montecarlo models

montecarlo models predictions

number of b

leadinglog order estimates

bbbar pair

flavor creation subprocesses

heavy quark production

qcd hard