Study of B and BD(*)Matthew Barrett

Brunel University – HEP GroupSchool of Engineering and Design

On Behalf of the BaBar Collaboration

Presented at

Outline● Recoil Technique● B ● BD(*)● Summary

08 June 2008 Matthew Barrett – Brunel University 2

Experiment

e+

e–

SVT – Silicon Vertex Tracker

1.5T Magnet

DIRC – Detector of Internally Reflected Cherenkov radiation

DCH – Drift CHamber

EMC – Electromagnetic Calorimeter

IFR – Instrumented Flux Return

● e+e– collisions: ECM

= 10.58GeV (Y(4S) Mass).

433 fb–1 4S data

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Recoil Technique● Lack of kinematic

constraints: 2 or 3 neutrinos in final state.

● Fully Reconstruct otherB (B

reco): constrain Bsignal.

● Two methods – “Tags”:● Hadronic: B

recoD(*)X

– X= hadrons (, K, 0, Ks).

● Semileptonic: BrecoDlX

– X = 0, nothing. (assume 1 missing) Fully Reconstruct08 June 2008 Matthew Barrett – Brunel University 4

Recoil Technique● The is reconstructed

in 4 modes in B.

– ee

–

–

–

● Accounts for ~70% of decays.● Only Leptonic decays used in BD

Fully Reconstruct08 June 2008 Matthew Barrett – Brunel University 5

B

B Motivation●

● ml leads to Helicity suppression:

I● fB: B-meson decay constant.

− Accessible: purely leptonic decays.− fB = 0.216 0.022 GeV from lattice QCD.

● Vub

: CKM matrix element: |Vub| = (4.31 0.30) 10

–3.

● SM predictions: B(B) = (1.6 0.4) 10–4.B(B) = (0.85 0.14) 10–4. (Vub, no lattice)

Phys.Rev.Lett.95, 212001 (2005)

PDG2006

: : e1 : 510–3 : 10–7

wb

u

_ _

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B Motivation● Beyond the SM:● Extra diagram from Charged

Higgs.● Modified Branching fraction in

Two Higgs Doublet Model (2HDM):

● mH – charged Higgs Mass.

● tan – ratio of v.e.v. of 2HD.

W.S.Hou PRD 48 2342 (1993)

wb

u

_ _

Hb

u

_ _

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B Hadronic Analysis● Uses 383 106 BB pairs.● Likelihood fit to yield in

4 channels.●

●

● EExtra

sum of unattributed energy in Calorimeter.

●

Phys.Rev.D77:011107, 2008arXiv:0708.2260 [hep-ex]

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B Semileptonic Analysis● Uses 383 106 BB pairs.● Likelihood fit to yield in

4 channels.●

●

● EExtra

sum of unattributed energy in Calorimeter.

●

Phys.Rev.D76:052002, 2007arXiv:0705.1820 [hep-ex]

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Belle B Results● 449 106 BB pairs● Hadronic Tags (B D(*)0[, , a

1, D

s]).

●

●

● Using HFAG Vub:

PRL 97, 251802 (2006)

(3.5

mode

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B Results● BaBar: Two tags – statistically independent.● Combine – Likelihood fit to 8 channels● (2.6● Belle hadronic analysis:●

● UTfit combined value:● B(B) = (1.41 0.43) 10–4.

a● NB BaBar and Belle values above include

charge conjugate modes.

http://www.utfit.org

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Standard Model constraints● Combine with m

d:

– B0 mass difference.– fB cancels.

– ratio of CKM elements:|V

ub| and |V

td|.

– UT constraint.

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Constraints on New Physics● Constraint on Charged

Higgs Mass.●

● Shown above LEP direct search limit.

● Combine with results frombs. B + bs.

B

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BD(*)

BD(*) Motivation● Many Semileptonic B decays observed:● But those with a – experimentally challenging.● Branching fractions can be accurately predicted:

● 4 Channels to be studied

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JHEP 0610, 053 (2006)Phys. Lett. B 326 145 (1994)

BD(*) Motivation● Beyond SM – charged Higgs.● Higgs couples to mass – larger

effect than in BD(*)l● Ratio of

B(BDBBDlfor MSSM (l = e, ).

mW/m

H tan

hep-ph/0109244

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BD(*) Analysis● Uses 232106 BB pairs.● Hadronic tags used.● Flavour correlation between

D(*) and Breco

.

● Reconstruct 4 D channels:D*+, D*0, D+, D0

● Most discriminating variable mmiss

2

● Simultaneous fit to all channels.● BF normalised with respect to D(*)l

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BD(*) ResultsLegend

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BD(*) Results

●

Belle● 535106 BB pairs.● reconstructed as e,

and .●

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(3.6(6.2

PRL 100 021801(2008)hep-ex/0709:1698

Xmis

– closely related to Mmiss

.E

vis – visible energy.

signal

background

arXiv:0706.4429[hep-ex] (5.2

statonly

Summary● Leptonic and semi-leptonic B decays involving s are

experimentally challenging.● But provide exciting prospects for observing new

physics effects, including charged Higgs.

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Backup Slides

Charged Higgs Exclusion

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