Status of V ub from Belle

ICHEP2002 Amsterdam 7/25/2002 Youngjoon Kwon (Yonsei Univ. /Belle)

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Status of VStatus of Vubub from Belle from Belle

Appetizer: W-annihilation modes with Vub vertex

Entree:decay modes that we (can) use to measure Vub

Dessert: to finish with something sweet

Youngjoon KwonYonsei University

for the Belle collaboration

CourseCourse


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The Unitarity TrianlgeThe Unitarity Trianlge

0VVVVVV *** tbtdcbcdubud

tbtstd

cbcscd

ubusud

VVVVVVVVV

CKMV

*Vub tdV

*VV cbcd

1

2

3

1VV tbud

* other triangles are difficult to measure


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– uncertainty in fB– BF is very small for (helicity suppression)

– or experimentally very messy due to multiple neutrinos for

– a good place to search for new physics

WW-annihilation decays with -annihilation decays with VVubub vertex vertex

The cleanest mode with Vub vertex is fully leptonic B decays

B

,e

Bb

u

B

L

b

u

B

ubBf V W


4

Belle-CONF-0247


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B ResultsResults Fitting pl distribution

no evidence of signals => 90% CL upper limits

Preliminary

160 fbdtLON

Belle-CONF-0247


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Semileptonic Semileptonic BB decays for V decays for Vubub

Semileptonic B decays provide the best opportunity for measuring |Vub |- strong interaction effects are much simplified due to the two leptons in the final state

u... ,


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lB0

use detector hermeticity to “measure” undetected neutrino the events should be consistent with

– hermeticity assumption

|Qtotal| < 2 ; only one ID’ed lepton ; – only one missing neutral particle = neutrino

attribute missing (E,p) to the neutrino

VVub ub from from

omiss

o 15017


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lB0

1

1

9

60

fbdtL

fbdtL

OFF

ON


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Preliminary

lB0BF( ) & BF( ) & VVub ub

(Khodjamirian et al.)

PRD 62, 114002 (2000)


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qq22 distribution of distribution of BB l l

preliminary

)/GeV3.4/ns10(// 42122 cdqd

Unfolding of true q2 distribution

from observed distribution,

by considering efficiency/smearing


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eB

1

1

6

60

fbdtL

fbdtL

OFF

ON

Belle-CONF-0242


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eB

1573

1114

N(events) in the signal region

with 0.76 < m(3) < 0.81

(cont.) 2147 (fake) 22

)( 1048

)(total 15222cb

MC est.

Excess in m(3)

after side-band subtraction

= 59 15 events

Belle-CONF-0242


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eB Systematic uncertainties

– background est. 18.0%

– signal fitting 9.2%

– MC statistics 5.1%

– tracking 6.0%

– photon-finding 4.0%

– electron ID 3.0%

– Total: 22.3%preliminary

Belle-CONF-0242


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Similar “neutrino reconstruction”

using hermeticity

2-dim. fit to E vs. M()

9.0|cos|)(GeV/ 42

2 ||GeV/c 8.20.2

miss

222miss

total

cM

Qp

0B


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Projections onto E and M() Tentatively, using ISGW2 for

- efficiency, hence BF; and

- Vub

preliminary

1

1

3

29

fbdtL

fbdtL

OFF

ON 0B


16


17

preliminary

1

1

8

79

fbdtL

fbdtL

OFF

ON

Belle-CONF-0248

40* 104.1)(B sDBWe also have


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Using PDG2002 for Vcb,310)0.22.41(|V| cb

10)5.3(|V| 30.19.0

ub

preliminary


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160 fbdtLON*sDB

KK *

KKS

back to W-annihilation decay with Vub vertex same 3 Ds decay modes

preliminary

ss DD *

Belle-CONF-0247


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Conclusion Conclusion (1)(1)

preliminary


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Conclusion Conclusion (2)(2)

3

3

1063.028.015.058.3

1056.024.013.011.3Vub

UKQCD

Khodjamirian, et al.(LCSR)

From new measurement of

and using factorization-based calculation

10)5.3(|V| 30.19.0

ub

sDB0

preliminary

Backup slidesBackup slides


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• asymmetric energye+ (3.5 GeV) e- (8 GeV)

• design Luminosity = 1034 /cm2/s• E(cm) = 10.58 GeV on resonance of (4S) production

The KEKB The KEKB ColliderCollider


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The Belle detectorThe Belle detector

Documents

Status of V ub from Belle