B physics at BelleB physics at Belle

Koji Hara (Nagoya University)

Workshop "New Developments of Flavor Physics" 2009

March 9-10, 2009

New results of tauonic B decays

BandBD

KEKB & BelleKEKB & Belle

e+ source

Ares RF cavity

Belle detector

SCC RF(HER)

ARES(LER)

e- (8.0GeV) × e+ (3.5GeV)

⇒(4S) →BB

⇒Lorentz boost:= 0.425

Finite crossing angle

~11mrad ×2

Operation since 1999.

L peak = 1.71x1034cm-2s-1

2

Total: 895 fb-1

(4S): ~720 fb-1

(5S): ~52.6fb-1

(3S): 2.9 fb-1

(2S): 7.1fb-1

(1S): 5.7fb-1

Yb scan: 8.1fb-1

Off-peak: ~83 fb-1

Total: 895 fb-1

(4S): ~720 fb-1

(5S): ~52.6fb-1

(3S): 2.9 fb-1

(2S): 7.1fb-1

(1S): 5.7fb-1

Yb scan: 8.1fb-1

Off-peak: ~83 fb-1

3

BelleBelle DetectorDetector

4 lyr DSSD

He/C2H6

Extreme forward calorimeter

Leptonic decays proceed through W boson annihilation in the Standard Model

Decay rate simply related to B meson decay constant fB and |Vub|

Charged Higgs contribution enhance/reduce the Br

[Wei-Shu Hou Phys. Rev. D48, 2342 (1993)]

CP Violation may be sensitive to “unparticle” physics[ R. Zwicky, Phys.Rev.D77036004(2008), C.-S. Huang and X.-H. Wu, Phys.Rev.D77,075014(2008)]

4

BB++IntroductionIntroduction

b

uW/H

5

BB Analysis Concepts Analysis Concepts

Require no particle remain after removing products of tagging B and the particle(s) from B decay

Possible only in B factory

More than 2 neutrinos appear in B decay

Tagging side :Semileptonic or Hadronic B Decay

Signal side :

Detect daughter particle(s)

(4S)B- B+

e+

e

B++, +e+eB-X

Most powerful discriminant variable:Extra calorimeter energy EECL

6

Belle Hadronic B tag (449x106 BB pairs)[PRL 97, 251802 (2006)]

◦ 3.5 evidence

B(B)=[1.79 (stat) (syst) ] x 10-4

BaBar (383 x 106 BB pairs) [PRD 77, 011107(R) (2008)], [PRD 76, 052002 (2007)]

◦ Hadronic B Tag

◦ Semileptonic (BDlX) Tag

X: , 0,

not reconstructed explicitly

◦ 2.6excess

B(B)=[1.2±0.4(stat)±0.3(bkg)±0.2(syst)]×10-4

Previous BPrevious B++++Measurements Measurements

+0.56 　　　　　 +0.46 -0.49 -0.51

New Belle Result with D(*)l tag using 657M BB pairs

Need more statistics to establish B+ Decay

Belle Hadronic

BaBar DlXBaBar Hadronic

B=1x10-3 Signal

B=3x10-3 Signal

7

Signal Selection ConceptSignal Selection ConceptThough Br(BD(*)l)is large (~17%), S/N is expected to be

worse than S/N of hadronic B tags. We only use clean decay modes with high Br x .

Tagging Side◦ B- D*0l+ D0l

D*0D00, D0 D0K-+,K-, K-

◦ Reconstruct D*0lexplicitlypreventadditional fromcontaminating EECL

Signal Side1 prong decay◦ B+

e, ,

Require No additional charged tracks or

8

Tagging side◦ Identified using a kinematic relation

Optimized to maximize in EECL<0.2 GeV◦ separately for l and modes

Signal side◦ Nsig extracted from EECL

◦ Clear Signal and BG separation expected

Selection CriteriaSelection Criteria

signal (B =1.79x10-

4)

lDB

lDlDB

lDB PP

MMEEB

(*)

(*)(*)

(*)

2

2cos

22

EECL(GeV)

Eve

nts

/ 0

.05

Ge

V

BGsigsig NNN /FoM

D*l tag,

MC expectation

BG

+ Data+ BG

D*l tag, l + Data+ BG

Semileptonic Tag Semileptonic Tag BBResultResult

)()(154 2122

3635sig syststatN

435.037.0

38.037.0 10)]()(65.1[)(

syststatB B

[arXiv: 0809.3834, BELLE-CONF-0840]

3.8σ significance including systematics.

Confirmation of previous Belle result with hadronic tags (more precise)

Above SM expectation, discrepancy ~1.6σ

9

409.013.0SM 10]78.0[)(

BB (CKMfitter 2008 prediction)

Dominant systematic error for B(B): BG MC Statistics (12%), Tagging Efficiency(12%) Peaking BG Uncertainty (8%)

10

Determination of fDetermination of fBB

Product of B meson decay constant fB and CKM matrix element |Vub|

Using |Vub| = (4.47±0.30)×10-3 from Belle BXulinclusive

[Belle preliminary, CKM2008]

GeV10)1.17.9(V 40.11.1ubB

f

fB = 216 22 MeV (an unquenched lattice calc.)

[HPQCD, Phys. Rev. Lett. 95, 212001 (2005) ]

MeV 216 2728

2524B

f

11

rH=2.110.75

22 2

2(1 tan )B

HH

mr

m

Constraint on Charged HiggsConstraint on Charged Higgs435.038.0

37.037.0 10)65.1() (BB

95% C.L.

409.013.0SM 10]78.0[)(

BB

B→DB→D Introduction Introduction Semileptonic decay sensitive to charged Higgs

T.Miki, T.Mimuta and M.Tanaka:hep-ph 0109244.

1.Smaller theoretical uncertainty of R(D)For B→τν,

There is O(10%) fB uncertainty from lattice QCD

(Ulrich Nierste arXiv:0801.4938.)2.Large expected Br

Compare to B→τν

3.The decay shape of 3 body decay can be used to discriminate W+ and H+

4. Sensitive to different vertex B: H-b-u, BD: H-b-c

W/H

b c Ratio of to ,e could be reduced/enhanced significantly

12

Previous B→DPrevious B→D(*)(*) Measurements Measurements

Belle inclusive B tag :

5.2σ observation

Belle B→D*τνB→D was not measured

Babar B→D(*)τνBabar full reconstruction tag :

13

BBDD Analysis Method Analysis Method

Similar to B analysis

Υ(4S) BB

e

K

π

νe ντ ντ

Signal Side(B→D)

Tagging Side(B→Hadronic mode)

• Require no remaining particles in the event using EECL

• Additional discriminant variable: Missing Mass square MM2 of the event

to separate BDlBG (MM2 ~ ) from signal (MM2>)14

Tag Side ReconstructionTag Side Reconstructionfully reconstruct B0,B+ 657x106BB

(Belle preliminary) (Belle preliminary)

TotalB+→147 modesB0→133 modes

B+ B0

Beam constraint Mass :

N=6.05x105

eff. = 0.18%Purity = 51%

N=1.01x106

eff. = 0.31%Purity = 58%

15

Selection of B→DSelection of B→D(*)(*)D(*) decay modes τ selection

No additional charged particles and π0 remain in the event

Extra calorimeter Energy(EECL) 　　　 Select signals using Missing Mass square (MM2) 、

PCM(τ→X)

Dτν Selection

e,μ with lower momentum

-Main background: Semileptonic B decays ( D(*)lν )

-signal-Dlν-D*lν-Other BG

EECL

No remaining particles

even

ts/0

.1G

eV

-signal-Dlν-D*lν-Other BG

MM2

Separate D(*)lν and signal

-signal-Dlν-D*lν-Other BG

arb

itra

l

arb

itra

l16

B→DB→D Result Result

EECLMM2B+→Dτν

ObservedClear Signal

GeVGeV2/c4

even

ts/0

.4G

eV2/c

4

even

ts/0

.1G

eV

●data - Dτν - D*τν - BG

●data - Dτν - D*τν - BG

(EECL<0.2GeV) (MM2>2.0GeV2/c4)

EECLMM2B0→Dτν

GeVGeV2/c4

even

ts/0

.4G

eV2/c

4

even

ts/0

.1G

eV

●data - Dτν - D*τν - BG

●data - Dτν - D*τν - BG

(EECL<0.2GeV) (MM2>2.0GeV2/c4)

17

(3.8σ)

(2.6σ)

First evidence

•Plots are projection in the signal enhanced region

(Belle preliminary)

B→DB→D** Result Result

(Belle preliminary)

EECLMM2

B0→D*τν

GeVGeV2/c4

even

ts/0

.4G

eV2/c

4

even

ts/0

.1G

eV

●data - Dτν - D*τν - BG

●data - Dτν - D*τν - BG

(EECL<0.2GeV) (MM2>2.0GeV2/c4)

ObservedClear Signal

•Plots are projection in the signal enhanced region

EECLMM2

B+→D*τν

GeVGeV2/c4

even

ts/0

.4G

eV2/c

4

even

ts/0

.1G

eV

●data - Dτν - D*τν - BG

●data - Dτν - D*τν - BG

(EECL<0.2GeV)(MM2>2.0GeV2/c4)

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Determination of R(DDetermination of R(D(*)(*)))

Br(B+→Dτν) = 1.51 ± 0.15 [%]-0.39 -0.19

+0.41 +0.24

Br(B+→D*τν) = 3.04 ± 0.22 [%]-0.66 -0.47

+0.69 +0.40

Br(B0→Dτν) = 1.01 ± 0.10[%]-0.41 -0.11

+0.46 +0.13

Br(B0→D*τν) = 2.56 ± 0.10[%]-0.66 -0.22

+0.75 +0.31

(first error is stat second is systematic, third is D(*)lBr error)

(preliminary)

(preliminary)

Deviation from the SM expectation

B+→Dτν: 1.6σB0→Dτν: 0.5σ

Consistent within errors

Branching fraction

19

Working on charged Higgs constraint.

SummarySummary New measurement of Bwith semileptonic

tagging method confirms the evidence obtained by Belle haronic tag.Update of hadronic tagging will also come soon.

First BD measurement in Belle has been performed. We obtained first evidence of B+D0+decay.

Measurement of tauonic B decays are now well established. They are giving tight constraints on charged Higgs.

Future measurements in Super B Factory will be strict tests of new physics beyond the SM.

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21

Specific Luminosity With Crab Crossing @ Specific Luminosity With Crab Crossing @ KEKBKEKB

22

22 mrad crossing

3.06 bucket spacing Simulation

22 mrad

Simulationhead-on

Crab Crossing Data

Not as high as the expectation of simulationStill need more study to achieve the goal (2x specific luminosity)

Crab crossing since January 2007

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For emodes◦ Dominant BG: true D(*)lnu tagged B-decays looser tagging selection◦ -2.1<cosBDL<1.3, -2.6<cosBD*L<1.2, 0.5<P*l

tag<2.5◦ P*l

sig > 0.3For mode

◦ Suppress continuum and combinatorial BG tighter tagging selection◦ -1.1<cosB(*)DL<1.1,1.0<P*l

tag<2.2◦ 1.0<P*

sig < 2.4◦ |costhrust| < 0.9

Reconstruction efficiencyIncluding Br of decay modes and tagging side efficiency◦ e mode: 6.0 x 10-4

◦ mode: 3.8 x 10-4

◦ mode: 4.9 x 10-4

Selection Criteria and EfficiencySelection Criteria and Efficiency

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Systematic Errors of YieldSystematic Errors of Yield

BG PDF Shape +18.1 -17.2Signal PDF Shape +3.1 -3.2Br of Peaking BG +6.4 -13.0Rare B,bul, pair BG +5.9 -5.9Efficiency Ratio +0.5 -0.6

Total +20.3 -22.3

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Br Systematic ErrorBr Systematic Error+(%) -(%)

(Error for Efficiency)MC stat 0.9 0.9PID 1.3 1.3Br of 0.4 0.4Tracking 1.0 1.0Tagging Efficiency 11.6 11.6

Signal Yield 13.2 14.7

NBB 1.4 1.4

Total 21.2 22.2

Systematic errorSystematic errorsource B+→Dτν[%] B+→D*τν[%]

MM2 shape +9.1/-7.9 +10.0/-5.8

EECL shape +10.6/-7.6 +7.0/-9.7

Br(B→D**lν) ±0.4 +0.8/-0.0

D⇄D* cross feed +7.1/-6.9 +5.1/-5.3

Br(τ→lνν) ±0.3 ±0.3

Total 15.7/-12.9 +13.2/-15.4

source B0→Dτν[%] B0→D*τν[%]

MM2 shape +6.4/-5.8 +5.8/-6.1

EECL shape +9.0/-7.3 +9.8/-5.0

Br(B→D**lν) +4.5/-2.6 +0.6/-0.3

D⇄D* cross feed +5.8/-6.0 +3.5/-3.4

Br(τ→lνν) ±0.3 ±0.3

Total +13.3/-11.4 +12.0/-8.6