1

CP violation and the Belle Experiment

Jin Li

USTC

2010

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What is a symmetry?• Invariants of the system. (Space, time, rotation)

Momentum, Energy, Angular Momentum.

• Discrete symmetry.

3

Parity violation

C.S.Wu et. al., Phys. Rev. 105,

1413 (1957)

Observed Not observed

Experiment Parity inversion

4

Pion decay

Weak interaction: C and P are violated maximally.

5

1964: Discovery of CP violation

1999: Direct CP violation in kaon decay (KTeV and NA48)2001: CP violation in B meson (Belle and Babar)

Phys. Rev. Lett. 13, 138 (1964)

32( ) (2.0 0.4) 10B K

0 02 2 1

1( ) ( )

2

0 ( ) ( 1) 1L

K K K CP K

L CP

6

Matter and Antimatter in 1st 10−3s10−35 second#quark=#anti-quark

10−32-10−4 secondSlight excess of quark

10−3 second - NOW~109 photons per quark

Sakhalov’s 3 conditions (1967):1. Both C and CP violation 2. baryon number violating process3. existence of non-equiblium

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Quark mixingFlavor is not conserved in the weak interaction.

The weak eigenstates are not flavor eigenstates:

u c t

d s b

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CKM matrix

'

'

'

ud us ub

cd cs cb

td ts tb

CKM

d V V V d

s V V V s

b V V V b

V

1 0 0†

0 1 0

0 0 1

V V

# free parameters = 18 − 9 − 5 = 4

3x3 complex matrix

6 quark phases − 1 overall phase

+1 complexphase

3 Euler angles (3-D rotation)

9

Unitary TriangleWolfenstein’s parameterization ie

ie

Vcd Vcb*

1

2

3

3 A(1 i)3 A( i)

()

()

()

Vtd Vtb*Vud Vub

*

3A

Vud Vub* +Vcd Vcb

*+Vtd Vtb* = 0

2 4

2

/ 2 ( )

/ 2 ( )

(1 )CKM

A i

V A O

A i A

d b

(1,0)

()

()

()

()

_ __

_

= (12/2)

= (12/2)

_

_

Normalized

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Feynman diagrams

CP

*ij ijV V necessary for CP violation

Two amplitudes needed to account for phase redefinition.Direct CP violation as an example.

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Direct CP violationAmplitudes for CP conjugate

( )

( )s

f

f

A P f

A P f

A

A

Define

2 2

2 2

( ) ( )

( ) ( )

ffCPf

ff

A AP f P fa

P f P f A A

j j

j j

i if j

j

i ijf

j

A a e e

A a e e

j

j

Changes sign under CP“weak” phase

Does not change sign under CP“strong” phase

CP

2 2

,

2 sin( )sin( )f j k j k j kfj k

A A a a

CP conservation: ffA A

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CP violation mechanism

•At least two interfering amplitudes with comparable size•Different weak phases.•Different strong phases.

1 2 2 1 2 12 21 2 1 2 2 1 2 1

2 sin( )sin( )

cos( )cos( )CPf

a aa

a a a a

Two contributions to the amplitude

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An excellent example of direct CPV

3* iubV e

(World Average)

Interference between T & P

Tree Penguin

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The B mesonB0=d b , B0= b d, B+=u b, B−=b u ¯ ¯ ¯ ¯ ¯Heaviest quark with bound states.Long lifetime because of must decay outside of third family.Decay through “b→c” dominant, |b→c|2/|b→u|2 ≈100 .“penguin” in “b→s” transition.Flavor oscillation through “b↔t” box diagram.

In e+e− collider, can be produced by (4S) resonance.

•σ(e+e− →BB) ≈1nb

•B0B0/B+B− = 50/50

•Coherent 1− − P-wave

¯

¯

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Flavor Oscillation

0 0

0 02

( ) ( )

( ) ( )

B t B tdi

dt B tM

B

i

t

0 0

0 0

L

H

B p B q B

B p B q B

mass eigenstates:

2 22 212 12

*12 12

1( ) ( ) 4

4

4Re( )

m M

m M

H L H Lm m m

11 12 11 12* *12 22 12 222

M M i

M M

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Parameters in B0 mixing

12 12M

m

122m M

1

* * **12 12 22 12

*122

2i

itd tbi

td tb

M V VMqe

p M V Vm

12f if f

f

qAe

pA

0 ( /2) 0 0( ) cos sin2 2

i m i m mB t e t B i

pB

qt

0 ( /2) 0 0( ) cos sin2 2

i m i m mB t e t B i

qB

pt

Define

if final state f = CP eigenstate

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B0

B0

B0

B0

Time-dependent CP violation

fcpB0

B0

2cos m t

fA

2sin mq

i tp

fA

fcp

2cos m t

fA

2sin mp

i tq

fA

Same “strong” phase12f i

f ff

qAe

pA

2cos m t

2sin m t

2

0 ( )A B t f

0 ( )A B t f

Arg( )f

0 0

0 0

( ( ) ) ( ( ) )( )

( ( ) ) ( ( ) )

Im( )sin( )

CP

f

B t f B t fA t

B t f B t f

mt

Case |λf| = 1

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B0→J/Ψ KS

,

0

0

0 mixing mix

*

*/

* * *

* * *

c ingDe ay

S L

B

cb csJ K

cb csd K

tb td cb cs cs cd

tb td c

K

b cs cs cd

V Vq q

p V V p

V V V V V V

V V V V V V

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,

2

/ S L

i

J Ke

Theoretically cleanClear experimental signaturesRelatively large BF

0 0, ,

1/ /( ) Im( )sin( ) sin 2 sin( )

S L S L

CP

J K J KA t mt mt

12f if f

f

qAe

pA

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Now: Precise measurementNow: Precise measurement

19191919

B0 tag_B0 tag

_465M BB535M BB

BJ/Ks

BJ/KL

_(cc)K(*)0

[PRD 79,072009(2009)]

CP-odd

CP-even

0.687 0.028 0.012sin2= 0.650 0.029 0.018

[PRL 98,031802(07)+PRD77 091103(08)]

Av. 0.670 0.023: 3.4% error !+(2S)KS

14000signals

12000signals

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Comparison to Kaon system0

, 0 0

( , 0) 11 2

( , 0) 1K

I

qA K I

pA K I

3, 0Im( ) 2 Im( ) ( 3.14 0.04) 10I

3, 0Re( ) 1 2Re( ) ( 3.31 0.04) 10I

/ 1Im( ) sin 2 0.670 0.023SJ K

CP violation in B0 system far greater than in K0 system.

•In B physics, the physical states cannot be isolated. One startes with pure B0 or B0 initial states. Parameter λf is natural.•In K physics, the physical states are well-isolated, thanks to very different lifeimes. Parameter ε is natural.

0

0

( , 0)

( , 0)L

S

A K I

A K I

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CPV meas. at B-factories

2121

Flavor-tag (B0 or B0 ?)

J/

KS

e

e

zt=0fCP

Vertexing

Reconstruction

ExtractCPV

fitB0B0

B0-tag B0-tag

t z/c

eff ~30%

t~1.4ps

=0.425 (KEKB)0.56 (PEP-II)

Inclusive info.(lepton, K etc.)

Pro

b.

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e+ source

Ares RF cavity

Belle detector

World record: L = 1.7 x

1034/cm2/sec

SCC RF(HER)

ARES(LER)

The KEKB Collider (Tsukuba, Japan)

8 x 3.5 GeV 22 mrad crossing angle

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The Belle Detector

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Belle uses double-sided silicon strip detectors to measure Δz.

KEKB/Belle: βγ = 0.425

Beam spot: 110 μm x 5 μm x 0.35 cm

Vertex resolutions(Belle): (σ(zcp) = 75μm; σ(ztag) =140μm)

4 layers, radiation hard readout, r = 1.5 cm

Decay distance increased by x 10

50m

Measuring the sub-picosecond time dependence of CPV

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New Physics in CP violation

Selected topics:

•Direct CP violation in B0 system.•The penguin b→sss process.•CP violation in exclusive b →sγ process.

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Revisit Direct CP violation in B→K

Belle Results: Nature 452, 332 (2008)

Acp(K) = { Belle

BaBar

CDF CLEO

Acp(K) = { BaBar

Belle CLEO

@2.0 AVG

@ AVG

AK = cp(K-

Acp(K) = @ 5.3

Recent Update

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The Kπ “puzzle”

Enhancement of C ?

C ＞ T is needed (C/T = 0.3–0.6 in SM)

breakdown of theoretical understanding

Enhancement of PEW ?

Would indicate new physics.

Due to poor understanding of strong interactions?

C.-W.Chaing, et al., PRD 70, 034020

H.-n.Li,et al., PRD 72, 114005

Y.-Y.Charng, et al., PRD 71, 014036

W.-S.Hou, et al., PRL 95, 141601

S.Baek, et al., PRD 71, 057502

Baek & London PLB 653, 249

Feldmann, Jung & Mannel, JHEP 0808,066

C.-W.Chaing, et al., PRD 70, 034020

H.-n.Li,et al., PRD 72, 114005

Y.-Y.Charng, et al., PRD 71, 014036

W.-S.Hou, et al., PRL 95, 141601

S.Baek, et al., PRD 71, 057502

Baek & London PLB 653, 249

Feldmann, Jung & Mannel, JHEP 0808,066

Expectation from current theory

T & P are dominant AK ~ 0

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Isospin sum rule for ACP in BKM. Gronau, PLB 627, 82 (2005); D. Atwood & A. Soni, Phys. Rev. D 58, 036005(1998).

B →K A(K0+)=0.009 ±0.025 A(K+0)=0.050 ±0.025 A(K+-)=-0.098 ±0.012 A(K00)=-0.01 ±0.10

HFAG, ICHEP08 A(K00)

A(K0+)

sum rule

measured (HFAG)

expected (sum rule)

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Non-KM CP violation in penguins : no KM phasetsV

Decay amplitude does not bringnew phase.

In SM: sin2Φ1eff=sin2Φ1 in B0→ J/ΨKS

12 holdsif

qe

p

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New Physics may enter b→s loops

0SK

0B

b

s

s

sd d

0SK

0B

b

s

s

sd d

Many new phases are possible in SUSY

O(1) effect allowedeven if SUSY scale is above 2TeV.

Large effects, O(0.1-0.2), are also possible in extra dimensional models e.g.with a 3 TeV Kaluza-Klein (K.K) particle.

e.g. K. Agashe, G. Perez, A. Soni,

PRD 71, 016002 (2005)

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Summary of sin2Φ1eff measurements

0.44± 0.170.18

0.59±0.07

0.74±0.17

sin2Φ1=0.67±0.02

Need more data to clarifyIf there’s deviation.

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Right-handed currents in exclusive bsγ processes

• Time dependent CPV in B0 (KS0)K*γ

– SM: γis polarized, the final state almost flavor-specific.

S(KS0γ) ~ -2ms/mbsin21

– mheavy/mb enhancement for right-handed currents in many new

physics models (left-right symmetric, extra dimensions etc)

– No need for a new CPV phase (right handed currents

suffice)

b

b

Ls

Rs

mb

mb

msms

D.Atwood, M.Gronau, A.Soni, PRL79, 185 (1997)D.Atwood, T.Gershon, M.Hazumi, A.Soni, PRD71, 076003 (2005)

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Right handed currents ? e.g. new mode BKS 0 γ

BKS+- γ

Require M() consistent with a 0 meson

Use the 0+ - decay for the

vertex in the silicon. Does not require KS vertexing in the silicon c.f BKS0 γ

Effective CP parameters in the 0 region

Good tags:

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SCP mesurement in exclusive b→sγ

Opposite C

353535

Crab cavities installed and undergoing testing in beam

The superconducting cavities will be upgraded to absorb more higher-order mode power up to 50 kW.

The beam pipes and all vacuum components will be replaced with higher-current design.

The state-of-art ARES copper cavities will be upgraded with higher energy storage ratio to support higher current.

SuperKEKB

e- 4.1 A

e+ 9.4 A

Aiming 8 × 1035 cm-2s-1

L 2ere

1 y

*

x*

Iy

y*

RL

Ry

Damping ring

3535

New IR*y = σz = 3 mm

Higher currentMore RFNew vacuum system

Crab crossing

+ Linac upgrade

8 GeV

3.5 GeV

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New Physics in Super B factory

50ab-1

CKM UT triangle Now NP effect

sin2φ1 = 0.87+-.09{Lunghi+Soni,hep-ph/08034340}

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Summary

• CP violation is caused by two amplitudes and a common phase.

• Mixing-induced CP violation in B0 system is much larger than in K0 system.

• New Physics in CP violation will be probed by Belle-II.

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BACKUP

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Flavor Oscillations

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Δm and ΔΓ

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D0 mixing

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NP in D0 mixing

1, 2, 3@ 50 ab-1

D0-mixing

LFV, CPV in D/ : Clear Indication of New Physics !

)10(~2

~ 352

OA

0;0)2

1(Im iM

f

f eA

A

A

p

q

CPV in D system negligible in SM

CPV in interf. mix./decay:

Currently ~±200

50 ab-1 go below 20