Oct 14, 2003;Pittsburgh, PA

Takeo Higuchi, KEKBEAUTY2003

Takeo HiguchiInstitute of Particle and Nuclear Studies, KEK

for the Belle collaboration

Hot Topicsfrom the Belle Experiment

Hot Topicsfrom the Belle Experiment

• Introduction to the Belle experiment• CP violation in B

0 KS

• Evidence of B

0 00• New resonance X(3872)• Summary

ContentsContents

Introduction to the Belle Experiment

Introduction to the Belle Experiment

e+e

3km circumferenceL = (1.06 1034)/cm2/sec L dt = 158 fb1

On-resonance 140 fb1

L = (1.06 1034)/cm2/sec L dt = 158 fb1

On-resonance 140 fb1

World Records

HistoryHistory

1999 Jun 2003 Jul

• 3.5 GeV e+ 8.0 GeV e

– e+e (4S) with = 0.425.– Crossing angle = ±11 mrad.

KEKB Accelerator KEKB Accelerator

Belle DetectorBelle Detector

KL detector14/15 layer RPC+Fe

Electromagnetic Calorimeter

CsI(Tl) 16X0

Aerogel Cherenkov Counter n = 1.015~1.030

Si Vertex Detector3 layer DSSD

TOF counter

8.0 GeV e

3.5 GeV e+

Central Drift ChamberTracking + dE/dx50-layers + He/C2H5

PeoplePeople

274 authors, 45 institutions274 authors, 45 institutions many nationsmany nations274 authors, 45 institutions274 authors, 45 institutions many nationsmany nations

CP Violation in B

0 KSCP Violation in B

0 KS

CP Violation by Kobayashi-MaskawaCP Violation by Kobayashi-Maskawa

2

2

)1(

2/

)(2/

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(1, 2, 3) = (, , )

CP violation parameters(1, 2, 3) = (, , )

O

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

Inputs: f = 1, S = 0.6A = 0.0

0d CPB f0

d CPB f

2

2 2

: eigenvalue

2 Im( ) | | 1,

| | 1 | | 1

f

AS

CP

A = 0 or || = 1 No direct CPV

S = fsin21: SM prediction

New Physics Hunting in b sqqNew Physics Hunting in b sqq

+

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 sqq

New physics may deviate CPV in b ccs from sqq

b ccs Reconstructionb ccs Reconstruction

5417 events are used in the fit.

140 fb1, 152M BB pairs

J/ KL signal

B 0 J/KL

b ccs w/o J/KL

pB* (cms)

Beam-energy constrained mass (GeV/c2)

Detail by K.MiyabayashiDetail by K.Miyabayashi

CP Violation in b ccs CP Violation in b ccs

5417 events @ 152M BB

1sin 2

0.733 0.057 0.028

1sin 2

0.733 0.057 0.028

1.007 0.041 (stat)ccs 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 KS: K+K, KS – Minimal kaon-identification requirements.– Belle standard KS selection.– | M(KK) M(| < 10MeV/c2

(mass resolution = 3.6 MeV/c2).– | p| 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:

– KKKS: (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:

– KKKS: (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 KS– More stringent kaon-identification requirements.– Particle veto for ,D0, c0, and J/ KK and D+ KKS.– Belle standard continuum suppression.– | E | < 40 MeV, 5.27 < Mbc < 5.29 GeV/c2.

• B0 ´KS: 1) ´ , +2) ´ +,

– Belle standard continuum suppression.– |E| < 60MeV (´ ; 100 < E < +80 MeV (´ )

5.27 < Mbc < 5.29 GeV/c2

B 0 KS

B 0 KKKS

B 0 KS

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

Beam-Energy Constrained MassBeam-Energy Constrained Mass

6811 signals106 candidates for S and A fitpurity = 0.640.10efficiency = 27.3%

24421 signals421 candidates for S and A fitpurity = 0.580.05efficiency = 17.7% (´ ) 15.7% (´ )

19918 signals361 candidates for S and A fitpurity = 0.550.05efficiency = 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

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

B0 KS B0 KKKS B0 ’KS

fS

A

09.011.050.096.0

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 -track pair.

Fit sin21

@ 152M BB

Consistency ChecksConsistency Checks

• CP violation parameters with A = 0– B0 KS: fS = 0.99 ± 0.50

– B0 KKKS: fS = 0.54 ± 0.24

– B0 KS: fS = 0.43 ± 0.27

• Null asymmetry tests for S term– B K: fS = 0.09 ± 0.26

– B K: fS = 0.10 ± 0.14

Less correlationbtw S and A

Less correlationbtw S and A

26.009.0 S

Consistent with S = 0Consistent with S = 0

Statistical SignificanceStatistical Significance

sin21

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

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

• B0 KKKS, ´KS

– Consistent with sin21.

• B0 KS

– 3.5 deviation (Feldman-Cousins).– S(KS) = sin21: 0.05% probability.

0( )SS K

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

Evidence of B

0 0 0Evidence of B

0 0 0

Two possible diagrams require measured 2 disentangledTwo possible diagrams require measured 2 disentangled

Disentangling 2Disentangling 2

b u

d

u

W

W

d

u

u

bt

B0 is one of promising decays to measure 2B0 is one of promising decays to measure 2

TT PP

22, 1 sin 2( )A S A 22, 1 sin 2( )A S A

Penguin-polluted CP violation

Br(B0 0 0) measurement gives constraint on .

eff2

B0 00 ReconstructionB0 00 Reconstruction

• B0 reconstruction– 2 0’s with 115 < M() < 152 MeV/c2.– Efficiency = 9.90 ± 0.03%.

– Those MC-determined distributions are used in extraction of signal yield with calibration using B D0 decays in data.

Signal MC Signal MC

E [GeV]Mbc [GeV/c2]

Continuum SuppressionContinuum Suppression

Fisher

|cosB|

|r|

Multi-dimensionallikelihood ratio

Continuum

Signal MC

e+e BB eeqq

• 1cos2 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 0 ContaminationB 0 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 0 are negligible.

According to MC study, other charmless decays than B 0 are negligible.

Br(B 0) measurement: B. Aubert et al. [BaBar collaboration], hep-ex/0307087, submitted to PRL.

B 0

0

B 0

E [GeV] Mbc [GeV/c2]

charmless background incl. 0

Signal ExtractionSignal Extraction

Mbc [GeV/c2] E [GeV]

@ 152 M BB

B 0 (modeled by MC)

Signal

Continuum

Signal yield: Signal yield: 9.78.425.6SN

Unbinned maximum likelihood fit

Branching fraction Branching fraction0 0 0

6

( )

(1.7 0.6 0.2) 10

Br B

Signal shape is modeled by MC, and is calibrated using B D0 decays in data.

Significance incl. systematic error = 3.4S.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 J/New Narrow Resonance: X J/

• Mass distribution:

Data MC

( / ) ( / )M J M J

(2S) (2S)

X

New resonance X is found.

[GeV/c2][GeV/c2]

Eve

nts

/ 0.0

10 G

eV/c

2

•

• conversion elimination

2

( ) ( / )

20MeV/

M M J

c

2( ) 400MeV/M c

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]

MbcMJ/ 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 c meas meas PDG 2(2 ) (2 ) 3872.0 0.6 0.5 MeV/X X S SM M M M c

2

( / )2.3 MeV/

M Jc

2

( / )2.3 MeV/

M Jc

sig 35.7 6.8N 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

( ) ( / )

0.063 0.012 0.007( (2 )) ( (2 ) / )

Br B K X Br X J

Br B K S Br S J

@ 152M BB

What is X?What is X?

• Hypothesis I: 13D2

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

– (13D2 c1)/(13D2 J) ~ 5, while (X c1)/(X J) < 1

Mbc

M(c1)

No clear signal

1( ) / ( / ) 0.89 @ 90% CLcX X J 1( ) / ( / ) 0.89 @ 90% CLcX X J

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 II: “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

• 3.5 deviation is observed with Feldman-Cousins in CP violation in B

0 KS from the SM. Hint of new physics?

• Br(B 0 00) = (1.7±0.6±0.2)×106 is measured, wh

ich gives constraint on penguin uncertainty in 2.

• New resonance of X J/ is observed at M(X) =

3872.0±0.6±0.5 MeV/c2 that does not look like cc state.

Backup SlidesBackup Slides

Mixing-Induced CP ViolationMixing-Induced CP Violation

B0

B0 B0

VtbV*

V*Vtb

KStd

td

Sanda, Bigi & Carter

1

2

2

( )td

i

V

e

b

d

b

d

t

t

W W

b

d

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 distributions

e e+e: 8.0 GeVe: 3.5 GeV

BCP

z

Btag

(4S) ~ 0.425

fCPfCP

( )

z

ct

( )

z

ct

z cB ~ 200 m

flavor tagflavor tag

Detail by K.MiyabayashiDetail by K.Miyabayashi

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

Sources Error

Flavor tag 0.014

Vertex reconstruction 0.013

Signal fraction (J/KL) 0.012

Signal fraction (other) 0.007

t resolution function 0.008

Fit bias 0.008

Btag decay interference 0.008

t background distribution < 0.005

mB, B < 0.005

Total 0.028

Small uncertainty inanalysis procedure

Small uncertainty inanalysis procedure

stat err. = 0.057

B0 KKKS: CP = 1 MixtureB0 KKKS: 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 KKKS 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

CP = 1 = odd = even

Using isospin symmetry,

　　　　　　　 CP even　　　　　　　 CP even%015

100

B0 KKKS: CP = 1 Mixture Cont’dB0 KKKS: CP = 1 Mixture Cont’d

t Distributionst Distributions

t [ps] t [ps]t [ps]

B0 KSB0 KS B0 KKKSB0 KKKS B0 ’KSB0 ’KS

qf = 1

qf = 1

qf = 1

qf = 1

qf = 1

qf = 1

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

S A S A S A Wtag fractions ±0.018 ±0.007 ±0.005 ±0.006 ±0.005 ±0.007 Physics parameters ±0.033 ±0.002 ±0.006 ±0.002 ±0.003 ±0.003 Vertexing ±0.022 ±0.046 ±0.016 ±0.027 ±0.044 ±0.024 Background fraction ±0.053 ±0.035 ±0.045 ±0.026 ±0.029

±0.036 Background t ±0.015 ±0.008 ±0.003 ±0.003 ±0.010 ±0.006 Resolution function ±0.013 ±0.005 ±0.004 ±0.003 ±0.007 ±0.004 KKKs + f

0Ks bkg. +0.001 ±0.039

-0.084 Sum +0.09 ±0.07 ±0.05 ±0.04 ±0.05 ±0.04 -0.11

KS 'KS KKK

S

Systematics are small and well understood from b ccs studies.

Systematic UncertaintySystematic Uncertainty

Sources NS NS

E peak position 0.03 0.04

E width 0.62 0.45

Mbc peak position 0.04 0.04

Mbc width 0.69 0.67

Rare B (+0) 0.99 1.33

Total 3.34 3.43

Sources Eff Eff

Fitting 5.3% 6.1%

0 efficiency 7.0% 7.0%

MDLR selection 2.0% 2.0%

Luminosity 0.5% 0.5%

Total % 9.5%

M() DistributionM() Distribution

M() [GeV/c2]

Fit to -mass is pretty good

– M() can be fitted by -mass distribution well.– 13D2 J/ is forbidden by isospin conservation rule.

Constraint on Constraint on

0 0A A

00A

1

2A

1

2A

00A2

Amp(B )Amp(B )Amp(B )Amp(B )Amp(B )Amp(B )

AA

0A

0A

00A

00A

0 00 2 012

0 2

( )cos 2

1

B B B B B

B B A

0 00 2 012

0 2

( )cos 2

1

B B B B B

B B A

( )ij i jB Br B

• B0/B = 1.04• B00/B = 0.39• A = 0.57

Using Our Results

eff2 2| | | | 44.0 (90%C.L.) eff2 2| | | | 44.0 (90%C.L.)

Belle PreliminaryBelle Preliminary

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