Oct 14, 2003;Pittsburgh, PA

Takeo Higuchi, KEKBEAUTY2003

Takeo HiguchiInstitute of Particle and Nuclear Studies, KEK

for the Belle collaboration

Hot Topicsfrom the Belle Exper iment

Hot Topicsfrom the Belle Exper iment

• Introduction to the Belle exper iment

• CP violation in B0 →→→→ φφφφKS

• Evidence of B0 →→→→ ππππ 0ππππ 0

• New resonance X(3872)• Summary

ContentsContents

Introduction to the Belle Exper iment

Introduction to the Belle Exper iment

e+e−

3km circumferenceL = (1.06 ×××× 1034)/cm2/sec���� L dt = 158 fb−−−−1

On-resonance 140 fb−−−−1

L = (1.06 ×××× 1034)/cm2/sec���� L dt = 158 fb−−−−1

On-resonance 140 fb−−−−1

World Records

HistoryHistory

1999 Jun 2003 Jul

• 3.5 GeV e+ ×××× 8.0 GeV e−

– e+e− → ϒ(4S) with βγ = 0.425.

– Crossing angle = ±11 mrad.

KEKB Accelerator KEKB Accelerator

Belle DetectorBelle Detector

KL µµµµ detector14/15 layer RPC+Fe

Electromagnetic Calor imeterCsI(Tl) 16X0

Aerogel Cherenkov Countern = 1.015~1.030

Si Vertex Detector3 layer DSSD

TOF counter

8.0 GeV e−−−−

3.5 GeV e+

Central Dr ift ChamberTracking + dE/dx50-layers + He/C2H5

PeoplePeople

274 authors, 45 institutionsmany nations

274 274 authors, 45 institutionsauthors, 45 institutionsmany nationsmany nations

CP Violation in B0 →→→→ φφφφKSCP Violation in B0 →→→→ φφφφKS

CP Violation by Kobayashi-MaskawaCP Violation by Kobayashi-Maskawa

���

�

�

���

�

�

1−−−−1−

−−1=���

�

�

���

�

�

3

2

32

2

2

)1(

2/

)(2/

ληρλλλλ

ηρλλλ

AiA

A

iA

VVV

VVV

VVV

tbtstd

cbcscd

ubusud

KM ansatz: CP violation is due tocomplex phase in quark mixing matrix

KM ansatz: CP violation is due tocomplex phase in quark mixing matrix

unitarity triangle

CP violation parameters(φ1, φ2, φ3) = (β, α, γ)

CP violation parameters(φ1, φ2, φ3) = (β, α, γ)

O ρ

η

Time-Dependent CP AsymmetryTime-Dependent CP Asymmetry

0 0

0 0

0 0

( ) ( )( ) sin cos

( ) ( )

d CP d CPB B

d CP d CP

B f B fA t m At m

B f fS t

B

Γ → − Γ →= = − ⋅ ∆ + ⋅ ∆Γ → + Γ →

Inputs: ξf = −1, S = 0.6A = 0.0

0d CPB f→0

d CPB f→

2

2 2

: eigenvalue

2Im( ) | | 1,

| | 1 | | 1

f

AS

CPξ

λ λλ λ

−= =+ +

A = 0 or |λ| = 1 → No direct CPV

S = −ξfsin2φ1: SM prediction

New Physics Hunting in b →→→→ sqqNew Physics Hunting in b →→→→ sqq

b

d

s

d

s

s

φ

Ks

B0

W

gt

d d

s

s Ks

η’

B0 g

g~b s

+(δ 23

dRR)b~R

s~R

φ+

New process w/ different CP phase

New process w/ different CP phaseSM penguinSM penguin

Deviation from b →→→→ ccs Hint of new physics

SM predicts same CPV in b →→→→ ccs and sqq.

SM predicts same CPV in b →→→→ ccs and sqq.

e.g.) squark penguin

New physics may deviate CPV in b →→→→ ccs from sqqNew physics may deviate CPV in b →→→→ ccs from sqq

b →→→→ ccs Reconstructionb →→→→ ccs Reconstruction

5417 events are used in the fit.

140 fb−1, 152M BB pairs

J/ψ KL signal

B 0 →→→→ J/ψψψψKL

b →→→→ ccs w/o J/ψψψψKL

pB* (cms)

Beam-energy constrained mass (GeV/c2)

Detail by K.MiyabayashiDetail by K.Miyabayashi

CP Violation in b →→→→ ccsCP Violation in b →→→→ ccs

5417 events @ 152M BB

1sin2

0.733 0.057 0.028

φ =± ±

1.007 0.041 (stat)ccsλ = ±consistent with no direct CPV

poor flavor tag

fine flavor tag

Small systematic uncertainty↓

Well controlled analysis technique

Small systematic uncertainty↓

Well controlled analysis technique

Detail by K.MiyabayashiDetail by K.Miyabayashi

K. Abe et al. [Belle collaboration], BELLE-CONF-0353.

b →→→→ sqq Reconstructionsb →→→→ sqq Reconstructions

• B0 →→→→ φφφφKS: φφφφ →→→→K+K−−−−, KS →→→→ ππππ++++ππππ−−−−

– Minimal kaon-identification requirements.– Belle standard KS selection.– | M(KK) − M(φ) | < 10MeV/c2

(mass resolution = 3.6 MeV/c2).– | pφ | in CMS > 2.0 GeV/c.– Belle standard continuum suppression (given later.)– | ∆E | < 60MeV, 5.27 < Mbc < 5.29 GeV/c2. M(KK) [GeV/c2]

• Background is dominated by continuum• CP in the background:

– K+K−KS: (7.2±1.7)%– f 0(980)KS:– These effects are included in the systematic error.

• Background is dominated by continuum• CP in the background:

– K+K−KS: (7.2±1.7)%– f 0(980)KS:– These effects are included in the systematic error.

1.91.5(1.6 )%+

−

b →→→→ sqq Reconstructions −−−− Cont’db →→→→ sqq Reconstructions −−−− Cont’d

• B0 →→→→ ΚΚΚΚ++++ΚΚΚΚ−−−−KS– More stringent kaon-identification requirements.– Particle veto for φ, D0, χc0, and J/ψ → K+K− and D+ → K+KS.– Belle standard continuum suppression.– | ∆E | < 40 MeV, 5.27 < Mbc < 5.29 GeV/c2.

• B0 →→→→ ηηηη´KS: 1) ηηηη´ →→→→ ργργργργ, ρρρρ →→→→ ππππ+ππππ−−−−

2) ηηηη´ →→→→ ηπηπηπηπ+ππππ−−−−, ηηηη →→→→ γγγγγγγγ– Belle standard continuum suppression.– |∆E| < 60MeV (η´ → ργ); −100 < ∆E < +80 MeV (η´ → ηπ+π−)

5.27 < Mbc < 5.29 GeV/c2

0

10

20

30

5.2 5.22 5.24 5.26 5.28 5.3

a) B0 → φK0s

0

50

100

5.2 5.22 5.24 5.26 5.28 5.3

b) B0 → K+K−K0s

Ent

ries

/ 0.0

025

GeV

/c2

0

50

100

150

5.2 5.22 5.24 5.26 5.28 5.3Mbc (GeV/c2)Mbc (GeV/c2)Mbc (GeV/c2)

c) B0 → η’K0s

B0 →→→→ φφφφKS

B0 →→→→ K++++K−−−−KS

B0 →→→→ ηηηη′′′′KS

2 cms 2 cms 2bc beam(GeV/ ) ( ) ( )BM c E p≡ −

Beam-Energy Constrained MassBeam-Energy Constrained Mass

68±11 signals106 candidates for Sand A fitpurity = 0.64±0.10efficiency = 27.3%

244±21 signals421 candidates for Sand A fitpurity = 0.58±0.05efficiency = 17.7% (η´→ ηπ+π−)

15.7% (η´→ ργ )

199±18 signals361 candidates for Sand A fitpurity = 0.55±0.05efficiency = 15.7%

Unbinned Maximum Likelihood FitUnbinned Maximum Likelihood Fit

1. fsig: Event by event signal probability

( )0 01 (1 2 ) sin( ) cos( )4

Bt

B BB

eq w m t m tS A

τ

τ

− ∆− − ∆ ∆ + ∆ ∆2. �sig:

3. R: ∆t resolution function

4. Pbkg: Background ∆t distribution

signal background

cand 2maximize

1

( , ) ( ; , ) 0N

ii

LL PA A

AtS S

S=

∂= ∆ → =∂ ∂∏

sig sig sig bkg( ; , ) P ( ; , ) (1 ) ( )i S SP t f t f P tA A R∆ = ⋅ ∆ ⊗ + − ⋅ ∆

CP Violation in b →→→→ sqqCP Violation in b →→→→ sqq

-1

-0.5

0

0.5

1

-7.5 -5 -2.5 0 2.5 5 7.5

Raw

Asy

mm

etry

0.0 < r ≤ 0.5

f) B0 → η’K0s

-1

-0.5

0

0.5

1

-7.5 -5 -2.5 0 2.5 5 7.5∆t (ps)∆t (ps)∆t (ps)

0.5 < r ≤ 1.0

g)

-1

-0.5

0

0.5

1

-7.5 -5 -2.5 0 2.5 5 7.5

Raw

Asy

mm

etry

0.0 < r ≤ 0.5

d) B0 → K+K−K0s

-1

-0.5

0

0.5

1

-7.5 -5 -2.5 0 2.5 5 7.5∆t (ps)∆t (ps)∆t (ps)

0.5 < r ≤ 1.0

e)

-1

-0.5

0

0.5

1

-7.5 -5 -2.5 0 2.5 5 7.5

Raw

Asy

mm

etry

0.0 < r ≤ 0.5

b) B0 → φK0s

-1

-0.5

0

0.5

1

-7.5 -5 -2.5 0 2.5 5 7.5∆t (ps)∆t (ps)∆t (ps)

0.5 < r ≤ 1.0

c)

B0 →→→→ φφφφKS B0 →→→→ K+K−KS B0 →→→→ ηηηη’KS

A

−−−−ξξξξfS09.011.050.096.0 +

−±−

07.029.015.0 ±±−

18.000.005.026.051.0 +

−±±+

04.016.017.0 ±±−

05.027.043.0 ±±+

04.016.001.0 ±±−

B → fCP(sqq) decay vertices are reconstructed using K- or π-track pair.

Fitsin2φφφφ1@ 152M BB

Consistency ChecksConsistency Checks

• CP violation parameters with A = 0– B0 → φKS: −ξfS = −0.99 ± 0.50

– B0 → K+K−KS: −ξfS= +0.54 ± 0.24

– B0 → η′KS: −ξfS= +0.43 ± 0.27

• Null asymmetry tests for S term– B+ → φK+: −ξfS= −0.09 ± 0.26

– B+ → η′K+: −ξfS= +0.10 ± 0.14

Less correlationbtw Sand A

Less correlationbtw Sand A

26.009.0 ±−=S

Consistent with S = 0Consistent with S = 0

Statistical SignificanceStatistical Significance

0

2

4

6

8

10

12

14

16

-2 -1.5 -1 -0.5 0 0.5 1

-2ln

(L/L

max

)

S(φK0s)

a)

sin2φ1

Hint of new physics?Need more data to establish conclusion.

Hint of new physics?Need more data to establish conclusion.

• B0 →→→→ K++++K−−−−KS, ηηηη KS

– Consistent with sin2φ1.

• B0 →→→→ φφφφKS

– 3.5σσσσ deviation (Feldman-Cousins).

– S(φKS) = sin2φ1: 0.05% probability.

0( )SS Kφ

K. Abe et al. [Belle collaboration], hep-ex/0308035, submitted to Phys. Rev. Lett.

Evidence of B0 →→→→ ππππ0ππππ0Evidence of B0 →→→→ ππππ0ππππ0

Two possible diagrams require measured φφφφ2 disentangledTwo possible diagrams require measured φφφφ2 disentangled

Disentangling φφφφ2Disentangling φφφφ2

b u

d

u

W

W

d

u

u

bt

B0 →→→→ ππππ ++++ππππ −−−− is one of promising decays to measure φφφφ2B0 →→→→ ππππ ++++ππππ −−−− is one of promising decays to measure φφφφ2

TT PP

22, 1 sin2( )A S Aππ ππ ππ φ θ= − +

Penguin-polluted CP violation

Br(B0 →→→→ ππππ 0ππππ 0) measurement gives constraint on θθθθ.

eff2φ

B0 →→→→ ππππ0ππππ0 ReconstructionB0 →→→→ ππππ0ππππ0 Reconstruction

• B0 reconstruction– 2 π 0’s with 115 < M(γγ) < 152 MeV/c2.

– Efficiency = 9.90 ± 0.03%.

– Those MC-determined distributions are used in extraction of signal yield with calibration using B+ → D0π+ decays in data.

Signal MC Signal MC

∆E [GeV]Mbc [GeV/c2]

Continuum SuppressionContinuum Suppression

Fisher

|cosθB|

|r|

Multi-dimensionallikelihood ratio

Continuum

Signal MC

e+e− → BB e+e− → qq

• 1−cos2θ for BB

• flat for qq

Construct likelihood

• r = high → well tagged→ originated from B decay

• r = low → poorly tagged→ originated from qq

Flavor tag quality

B flight direction

Fisher

sig

sig

MDLH 0.95qq

L

L L≡ >

+

B++++ →→→→ ρρρρ++++ππππ0 ContaminationB++++ →→→→ ρρρρ++++ππππ0 Contamination

• ∆E-Mbc shape: MC-determined 2-dimensional distribution.

• Yield: Recent Br measurement with MC-determined efficiency.

According to MC study, other charmless decays than B+ → ρ+π0 are negligible.

According to MC study, other charmless decays than B+ → ρ+π0 are negligible.

Br(B+ → ρ+π0) measurement: B. Aubert et al. [BaBar collaboration], hep-ex/0307087, submitted to PRL.

B+ → ρ+π0

π+π0

B+ → ρ+π0

∆E [GeV] Mbc [GeV/c2]

charmless background incl. ρ+π0

Signal ExtractionSignal Extraction

Mbc [GeV/c2] ∆E [GeV]

@ 152 M BB

B++++ →→→→ ρρρρ++++π π π π 0 (modeled by MC)

Signal

Continuum

Signal yield: Signal yield: 9.78.425.6SN +

−=Unbinned maximum likelihood fit

Branching fractionBranching fraction0 0 0

6

( )

(1.7 0.6 0.2) 10

Br B π π−

→

= ± ± ×

Signal shape is modeled by MC, and is calibrated using B+ → D0π+ decays in data.

Significance incl. systematic er ror = 3.4σσσσS.H.Lee, K.Suzuki et al. [Belle collaboration], hep-ex/0308040, submitted to Phys. Rev. Lett.

New Resonance X(3872)New Resonance X(3872)

New Narrow Resonance: X →→→→ ππππ++++ππππ−−−−J/ψψψψNew Narrow Resonance: X →→→→ ππππ++++ππππ−−−−J/ψψψψ

• Mass distr ibution:

Data MC

( / ) ( / )M J M Jπ π ψ ψ+ − −

ψψψψ(2S) ψψψψ(2S)

X

New resonance X is found.

[GeV/c2][GeV/c2]

Eve

nts

/ 0.0

10 G

eV/c

2

•

• γ conversion elimination

2

( ) ( / )

20MeV/

M M J

c

ψ+ − −

<

� �

2( ) 400MeV/M cπ π+ − >

B+ →→→→ K+XB+ →→→→ K+X

• B+ →→→→ K+X reconstruction– Add loosely identified kaon to X.

5.20 5.25 5.30 3.84 3.88 3.92 0.0 0.2[GeV/c2] [GeV/c2] [GeV]

Mbc MππJ/ψ ∆E

3-dim. unbinnedlikelihood fit.3-dim. unbinnedlikelihood fit.

meas meas PDG 2(2 ) (2 ) 3872.0 0.6 0.5 MeV/X X S SM M M M cψ ψ= − + = ± ±

2

( / )2.3 MeV/

M Jc

π π ψ+ −Γ <

sig 35.7 6.8N = ±

( ) ( / )0.063 0.012 0.007

( (2 )) ( (2 ) / )

Br B K X Br X J

Br B K S Br S J

π π ψψ ψ π π ψ

+ + + −

+ + + −→ × → = ± ±

→ × →

@ 152M BB

What is X?What is X?

• Hypothesis I : 13D2

– M(X) = 3872 MeV/c2 differs fromprediction: M(13D2) = 3810 MeV/c2.

– Γ(13D2 → γχc1)/Γ(13D2 → ππJ/ψ) ~ 5,while Γ(X → γχc1)/Γ(X → ππJ/ψ) < 1

Mbc

M(γχc1)

No clear signal

1( ) / ( / ) 0.89 @ 90% CLcX X Jγχ ππ ψΓ → Γ → <

E.Eichten et al., Phys. Rev. D21, 203 (1980);W.Buchmüller and S.-H.H.Tye, Phys. Rev. D24, 132 (1981).

What is X? −−−− Cont’dWhat is X? −−−− Cont’d

• Hypothesis I I : “ molecular” charmonium– M(X) = 3872 ± 0.6 ± 0.5 MeV.

– M(D0) + M(D0*) = 3871.2 ± 1.0 MeV.

– Do above facts suggest loosely bound D0-D0* state?

– Need more data to conclude.

QQ q q D0-D0* “molecule”

S.-K.Choi, S.L.Olsen et al. [Belle collaboration], hep-ex/0309032, submitted to Phys. Rev. Lett.

SummarySummary

SummarySummary

• 3.5σ deviation is observed with Feldman-Cousins in CP violation in B0 → φKS from the SM.� Hint of new physics?

• Br(B0 → π 0π 0) = (1.7±0.6±0.2)×106 is measured, which gives constraint on penguin uncertainty in φ2.

• New resonance of X → π+π−J/ψ is observed at M(X) = 3872.0±0.6±0.5 MeV/c2 that does not look like ccstate.

Backup SlidesBackup Slides

Mixing-Induced CP ViolationMixing-Induced CP Violation

B0

B0 B0

VtbV*

V*Vtb

φφφφ

KS++++td

td

Sanda, Bigi & Car ter

1

2

2

( )td

i

V

e φ

∗

−

∝

∝b

d

b

d

t

t

W W

b

d

φφφφ

KS

W

W

t

tg

g

d

s

s

s

d

s

s

s

Vtb Vts

Vtb Vts

How to Measure CP Violation?How to Measure CP Violation?

• Find B fCP decay• Identify (= “ tag” ) flavor of B fCP

• Measure decay-time difference: ∆∆∆∆t• Determine asymmetry in ∆∆∆∆t distr ibutions

e−−−− e+e−−−−: 8.0 GeVe++++: 3.5 GeV

BCP

∆∆∆∆z

Btag

ϒϒϒϒ(4S)βγβγβγβγ ~ 0.425

fCPfCP

( )

z

ct

βγ ϒ

∆ ∆�

∆∆∆∆z cβγτβγτβγτβγτB ~ 200 µµµµm

flavor tagflavor tag

Detail by K.MiyabayashiDetail by K.Miyabayashi

Systematic Error of CPV in b →→→→ ccsSystematic Error of CPV in b →→→→ ccs

< 0.005∆t background distribution

< 0.005∆mB, τB

0.028Total

0.008Btag decay interference

0.008Fit bias

0.008∆t resolution function

0.007Signal fraction (other)

0.012Signal fraction (J/ψKL)

0.013Vertex reconstruction

0.014Flavor tag

ErrorSources

Small uncer tainty inanalysis procedure

Small uncer tainty inanalysis procedure

stat err. = 0.057

B0 →→→→ K++++K−−−−KS: CP = ±±±±1 MixtureB0 →→→→ K++++K−−−−KS: CP = ±±±±1 Mixture

K-

KSB0

J=0 J=0J=0

J=0

�������� CP = (−−−−1)����CP = (−−−−1)����

decay

CP = +1 CP = +1

K+

CP = ±±±±1 fraction is equal to that of ���� =even/oddCP = ±±±±1 fraction is equal to that of ���� =even/odd

Since B0 → K+K−KS is 3-body decay,the final state is a mixture of CP = ±1.

How can we determine the mixing fraction?

�-even fraction in |K0K0> can be determined by |KSKS> system

��

Using isospin symmetry,

CP evenCP even%015

100+−

B0 →→→→ K++++K−−−−KS: CP = ±±±±1 Mixture −−−− Cont’dB0 →→→→ K++++K−−−−KS: CP = ±±±±1 Mixture −−−− Cont’d

∆∆∆∆t Distr ibutions∆∆∆∆t Distr ibutions

∆t [ps] ∆t [ps]∆t [ps]

B0 →→→→ φφφφKSB0 →→→→ φφφφKS B0 →→→→ K+K−KSB0 →→→→ K+K−KS B0 →→→→ ηηηη’KSB0 →→→→ ηηηη’KS

qξf = −1

qξf = +1

qξf = −1

qξf = +1

qξf = −1

qξf = +1

Systematic Errors of CPV in b →→→→ sqqSystematic Errors of CPV in b →→→→ sqq

S A S A S AWtag fractions

�� ��

0.018

�� ��

0.007

�� ��

0.005�� ��

0.006

�� ��

0.005

�� ��

0.007Physics parameters

�� ��

0.033

�� ��

0.002

�� ��

0.006�� ��

0.002

�� ��

0.003

�� ��

0.003Ver texing

�� ��

0.022

�� ��

0.046

�� ��

0.016�� ��

0.027

�� ��

0.044

�� ��

0.024Background fraction

�� ��

0.053

�� ��

0.035�� ��

0.045

�� ��

0.026

�� ��

0.029

�� ��

0.036Background ∆∆∆∆t

�� ��

0.015

�� ��

0.008�� ��

0.003

�� ��

0.003

�� ��

0.010

�� ��

0.006Resolution function

�� ��

0.013

�� ��

0.005�� ��

0.004

�� ��

0.003

�� ��

0.007

�� ��

0.004KKKs + f0Ks bkg. +0.001

�� ��

0.039-0.084

Sum +0.09 0.07 0.05 0.04 0.05 0.04-0.11

φφφφKS ηηηη'KS KKKS

Systematics are small and well understood from b → ccs studies.

Systematic Uncer taintySystematic Uncer tainty

+2.0%−2.0%MDLR selection

++++Eff−−−−EffSources

++++3.43−−−−3.34Total

−−−−9.09.09.09.0%

−0.5%

−7.0%

−5.3%

−0.99

−0.69

−0.04

−0.62

−0.03

−−−−∆∆∆∆NS

+0.5%Luminosity

++++9.5%Total

+7.0%π0 efficiency

+6.1%Fitting

+1.33Rare B (ρ+π0)

+0.67Mbc width

+0.04Mbc peak position

+0.45∆E width

+0.04∆E peak position

++++∆∆∆∆NSSources

M(ππππ++++ππππ−−−−) Distr ibutionM(ππππ++++ππππ−−−−) Distr ibution

M(π+π−) [GeV/c2]

Fit to ρρρρ-mass is pretty good

– M(π+π−) can be fitted by ρ-mass distribution well.

– 13D2 → ρJ/ψ is forbidden by isospin conservation rule.

Constraint on θθθθConstraint on θθθθ

0 0A A+ −= �

00A

1

2A+−

1

2A+−�

00A�2θ

Amp(B0 → π0π0)

Amp(B0 → π0π0)

Amp(B− → π−π0)

Amp(B+ → π+π0)

Amp(B0 → π+π−)

Amp(B0 → π+π−)

A+−�

A+−

0A−�

0A+

00A�

00A

0 00 2 012

0 2

( )cos2

1

B B B B B

B B Aππ

θ+− + +− +

+− +

+ + −≥

−

( )ij i jB Br B π π≡ →

• B++++0/B++++−−−− = 1.04• B00/B++++−−−− = 0.39• Aππππππππ = 0.57

Using Our Results

eff2 2| | | | 44.0 (90%C.L.)θ φ φ= − < �

Belle PreliminaryBelle Preliminary

M.Gronau et al., Phys. Lett. B 514, 315 (2001).