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Godparents: W. Wester, J. Dittman, G. Feild

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Godparents: W. Wester, J. Dittman, G. Feild. The B cross section. Introduction NLO calculation Previous measurements Final RUN 1 CDF measurement New theoretical developments Low energy SUSY and the b cross section Conclusion. D. Bortoletto Todd Keaffaber’s Thesis. Heavy quark NLO. - PowerPoint PPT Presentation
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Godparents: W. Wester, J. Dittman, G. Feild
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Page 1: Godparents: W. Wester, J. Dittman, G. Feild

Godparents: W. Wester, J. Dittman, G. Feild

Page 2: Godparents: W. Wester, J. Dittman, G. Feild

The B cross sectionThe B cross section

IntroductionNLO calculationPrevious measurements

Final RUN 1 CDF measurementNew theoretical developmentsLow energy SUSY and the b

cross sectionConclusion

D. Bortoletto

Todd Keaffaber’s Thesis

Page 3: Godparents: W. Wester, J. Dittman, G. Feild

Heavy quark NLOHeavy quark NLOCalculations of heavy quark production in hadronic

collisions follow the approach developed by Collins, Soper and Sterman:

Explicit calculation were done at NLO (O(s3)) by Nason,

Dawson and Ellis (NDE), Mangano Nason and Ridolfi (MNR)

Nason et al., Nucl., Phys. B327 (1989) 49, B335 (1990) 260W. Beenakker et al., Nucl. Phys. B351 (1991) 507M. Mangano et al., Nucl. Phys B373 (1992) 295

mOm;QQijdff

)m;QQHH(

QCD

ijH/jH/i

21

21

Page 4: Godparents: W. Wester, J. Dittman, G. Feild

Theoretical predictions are usually presented varying R and F in the range

The largest cross section (2) corresponds to large F and small

R

The uncertainty due to the PDF is small due to the tighter constraints set by DIS and HERA data (12-20%).

The mass of the b quark is varied between

In this range the cross section can change by about 10%

Heavy quark NLOHeavy quark NLO

2b

2T000

0 mp22

GeV575.4m5.4 b

Page 5: Godparents: W. Wester, J. Dittman, G. Feild

Heavy quark NLOHeavy quark NLO

The largest uncertainty in the cross section determination is the scale uncertainty which is sensitive to higher order corrections.

630GeV1800GeV0/

10GeV 20GeV

40GeV 60GeV

Page 6: Godparents: W. Wester, J. Dittman, G. Feild

Hadron collider experiments historically studied the b-quark cross section

More recently the differential cross section has also been studied.

Measurements have been performed using different data sets with electrons or muons and/or jets in the final state:

Inclusive decays e/Muon+jets J/

Experimental MeasurementsExperimental Measurements

T

2

pp

T

yy

minT dydp

ddpdy)p(minTTmax

uB+

K+

u u

Page 7: Godparents: W. Wester, J. Dittman, G. Feild

B cross section measurementsB cross section measurements

The single b inclusive cross section has been measured at several energies: 540 GeV by UA1 630 GeV by UA1,

CDF and D0 1.8 TeV by CDF

and D0

630 GeV630 GeV

Page 8: Godparents: W. Wester, J. Dittman, G. Feild

Early CDF measurementsEarly CDF measurements

1.8 TeV

Page 9: Godparents: W. Wester, J. Dittman, G. Feild

B cross section measurementsB cross section measurements

Excellent agreement between experiments

Significant excess in the data

1800 GeV

Page 10: Godparents: W. Wester, J. Dittman, G. Feild

B cross section measurementsB cross section measurements

The experimental measurements find a cross section higher than the theoretical prediction by a factor 2-3

630 GeV 1800 GeV

Page 11: Godparents: W. Wester, J. Dittman, G. Feild

Ratio of the cross section

Reduced theoretical and experimental uncertainties

B cross section measurementsB cross section measurements

)GeV1800(

)GeV630(b

b

Page 12: Godparents: W. Wester, J. Dittman, G. Feild

D0-b Jet measurementD0-b Jet measurementD0: b tagging jets using muons.Require ET(Jet)>25GeV, and PT()>6GeV

Agreement with theory upper band for pT>55 GeV

Page 13: Godparents: W. Wester, J. Dittman, G. Feild

Summary of the measurementsSummary of the measurements

Page 14: Godparents: W. Wester, J. Dittman, G. Feild

B cross sectionB cross section In Run 1A first measurement of the B cross section by

CDF. (PRL 75, 1451 (1995))

K/JB0*

K/JB0

GeV9)B(p6 T

GeV12)B(p9 T

GeV15)B(pT

GeV15)B(p12 T

Page 15: Godparents: W. Wester, J. Dittman, G. Feild

B cross sectionB cross sectionMeasurement confirms discrepancy between theory

and experiments

CDF published

2.02.09.1Theory

Data

Page 16: Godparents: W. Wester, J. Dittman, G. Feild

L=984 pb-1

Use only the decay

Require muons in SVX to have more precise ct information

Require CMU muons

Run 1 MeasurementRun 1 Measurement

L=19.30.7 pb-1

Use the decays

Muons can be both in SVX and CTC

Require CMU muons

RUN 1A RUN 1

K/JB

0*0* K/JB

K/JB

/J/J

Page 17: Godparents: W. Wester, J. Dittman, G. Feild

Track quality cuts 4 hits in at least 2 axial superlayers 2 hits in at least 2 stereo superlayersRexit(Kaon)>110 cm

Muons:All muons have CMU stubMuon matching

3 hits in the SVXPrimary vertex

Data SelectionData Selection

0.12)z(0.9)x( 22

cm60z

Page 18: Godparents: W. Wester, J. Dittman, G. Feild

J/J/ reconstruction reconstruction

c/GeV8.2)(p 2T

c/GeV8.2)(p 2T

c/GeV8.1)(p 1T

c/GeV8.1)(p 1T

c/GeV0.2)and(p 21T

Run 1A:

and

Run 1B

and

or

J/ reconstruction

+ - are vertex constrained

3.3MM /J

Page 19: Godparents: W. Wester, J. Dittman, G. Feild

B reconstruction SVX information used if available for the kaon + - K are vertex constrained + - mass constraint to J/ mass

Data SelectionData Selection

m100

1

)p(

pX)B(ct

BBT

BT/J

c/GeV0.6)B(pT

c/GeV25.1)K(pT

Page 20: Godparents: W. Wester, J. Dittman, G. Feild

Event yieldEvent yield Event yield

for Run 1 analysis

Page 21: Godparents: W. Wester, J. Dittman, G. Feild

The B meson cross section is determined using

whereMi and i mass and width from the kinematic fit

s=scale factor b=slope of the backgroundw=fit mass range

Fitting methodFitting method

backtotal

sigtotalsig

total

sig fN

)NN(f

N

NL

2

i

i

s

MM

2

1

i

sig es2

1f

w

1

2

wMbf iback

Page 22: Godparents: W. Wester, J. Dittman, G. Feild

Event yield in PEvent yield in PTT bins bins

Event yield for Run 1 analysis divided in 4 pT bins

Page 23: Godparents: W. Wester, J. Dittman, G. Feild

02T

2b0

0

P2

b

2pm2

002.0006.0c/GeV25.075.4m

The product of the acceptance and trigger efficiency was calculated with BGEN, QQ, QFL, DIMUTG using the MRST structure functions

The QCD-NLO MC was run with:

Results:

AcceptanceAcceptance

Page 24: Godparents: W. Wester, J. Dittman, G. Feild

Efficiencies that are not included in the MC acceptance were calculated using data

Efficiencies that are not equal in Run 1A and Run 1B are averaged and weighted by the luminosity

EfficiencyEfficiency

Page 25: Godparents: W. Wester, J. Dittman, G. Feild

The B meson cross section is determined using

Where: N is the number of B mesons from a unbinned likelihood

fit pT is the width of the pT bin

L is the corrected integrated luminosityA is the MC acceptance which included the trigger

efficiency. is the reconstruction efficiencyB=BR(B+ J/K+) BR(J/ +-)=(5.880.60) 10-5

Cross SectionCross Section

BALp2

N

dp

)B(d

TT

Page 26: Godparents: W. Wester, J. Dittman, G. Feild

The measured J/ cross section fell as a function of the instantaneous luminosity

We correct for this effect:

Luminosity CorrectionLuminosity Correction

04.088.0dtL

LdtR

dt)L(

)0(LdtL

L

Feild, Lewis CDF note 4769

Page 27: Godparents: W. Wester, J. Dittman, G. Feild

Systematic uncertaintiesSystematic uncertaintiesFully correlated

systematic uncertainties which do not depend on pT

Uncorrelated systematic uncertainties which depend on PT

Page 28: Godparents: W. Wester, J. Dittman, G. Feild

The measured cross section is:

To compare with the theory we plot the results at

Differential Cross SectionDifferential Cross Section

T

p

T

theory

TpT

theory

dpdp

d

p

1

dp

d T

T

Page 29: Godparents: W. Wester, J. Dittman, G. Feild

Differential Cross SectionDifferential Cross SectionThe cross section is higher

than the theoretical NLO

%72.L.C

4.02.09.2Theory

Data

Page 30: Godparents: W. Wester, J. Dittman, G. Feild

Total Cross SectionTotal Cross Section

PT>15GeV/c

4

1i i

i

T

BRAL2

N

)1,c/GeV6p(

nb)syst(26)syst(5)stat(28207

)c/GeV15p(

fcuc

T

b)syst(4.0)syststat(4.06.3

)1y,c/GeV6p(

fcuc

TB

QCD NLO central value 1.2 b

Replace the last bin of the differential cross section

CDF measures:

Page 31: Godparents: W. Wester, J. Dittman, G. Feild

Shape are well described by perturbative QCD Large discrepancy on the cross section measurement

Presence of higher order termsFragmentation effects Intrinsic kT of partonsNew physics

Fixed order calculation have terms

Which could be quite large for

Heavy quark NLOHeavy quark NLO

n

2s

n

2

2

s Q

sln)Q(and

m

Qln)Q(

1Q

sand1

m

Q22

2

Page 32: Godparents: W. Wester, J. Dittman, G. Feild

New Theoretical developmentsNew Theoretical developments

Variable Flavor Number Scheme (VFN) (F.I Olness, R.J. Scalise and Wu-Ki Tung hep-ph/9712494)

Hadronization of heavy quarksHarder bB fragmentation (Colangelo-Nason)

30% (40%) higher B cross section in the central (forward) region

z)z1()z(f

Page 33: Godparents: W. Wester, J. Dittman, G. Feild

New Theoretical developmentsNew Theoretical developments

Studies of the kT effect

Page 34: Godparents: W. Wester, J. Dittman, G. Feild

New Theoretical developmentsNew Theoretical developments

Correlated b production seems to disfavor large kT effects.

Page 35: Godparents: W. Wester, J. Dittman, G. Feild

….

Page 36: Godparents: W. Wester, J. Dittman, G. Feild

New Physics HypothesisNew Physics Hypothesis

Supersymmetry could make a substantial contribution to the observed b cross section

Berger, Tait, Wagner et al. have a model with intermediate mass gluinos that decay into b and sbottom

The contribution is large if

GeV52mGeV1510mb~g~

Page 37: Godparents: W. Wester, J. Dittman, G. Feild

New Physics HypothesisNew Physics Hypothesis

The new contribution peaks at

b quarks have and similar to QCD production

Authors claim that this scenario is not ruled out by current limits.

GeV15mp g~T

Page 38: Godparents: W. Wester, J. Dittman, G. Feild

ConclusionConclusionFinal run 1 measurement of the B cross

section confirms discrepancy with QCD NLO predictions

CDF and D0 measurements on different data sets give consistent measurements of the b cross section

NLO calculations model the shape but under-estimate b production

Puzzle in b production is now emerging also at LEP and at HERA

bbeeee

Page 39: Godparents: W. Wester, J. Dittman, G. Feild

B physics program at hadronic machines continues to be complementary to B-factoriesAll B species are producedHigh production cross section

Higher luminosity will bring higher statistic but also systematic effects that will need to be investigated.

Higher statistic will allow:To probe higher ET region

Investigate the possibility to study the b-fragmentation at the Tevatron

Correlation studies

Prospects for Run IIProspects for Run II


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