• Introduction : CP violation in the SM, constraints/consistency• Asymmetric B factories : KEKB/BELLE , PEPII/BABAR

• The experimental path to CP violation • First results• Prospects

Roy ALEKSANCEA Saclay, DAPNIA/SPPaleksan@hep.saclay.cea.fr

CMS Workshop on B and Physics Helsinki, Finland

May 30-June 1 , 2002

CP Violation at Asymmetric e+e- collidersA new era has started ...

As far as one looks, the univers seems to be made of matter (NB/N10-10)

What is the mechanism that lead to this situation ?

In 1967 Sakharov Suggested that theorigin might be due to• B • CPin a universe in thermal non-equilibrium

Is there any interaction distinguishing matter from antimatter ?

Is it a fundamental property ?

?

Why do we care about CP Violation ?

XB1

B2

f

1-f

XB1

B2

f

1-f

])1([])1([ 2121 BBBBXX ffff

B1 = - B1 B2 = - B2

Since antiparticles have opposite quantum numbers

)BB()( 21 ffIf XTo get NB 0

B1-B2 0 and f-f 0B CP

Unitarity Triangle Determination

C(0,0) B(1,0)

A()

cb

udub

V

VV

cb

tdtb

V

VV

*

0

)(0

)( sdsd BB Bd0 , ,

,,/ )()(0 DDKJB sd B D K

B D K

s s0

0

( ) ( )

( )

,

,

B c D

B D D

, ,

,

( )

( ) ( )

B u

B

, ,

,

0VVVVVV tdtbcdcbudub

4

23

22

32

112

1

21

O

AiA

A

iA

tbtstd

cbcscd

ubusud

CKM

VVV

VVV

VVV

V

B physics0

V

VV1

V

VV

cb

tdtb

cb

udub

from K decays

If is removed, triangle could be flat or upside down !!!

Most of the uncertaintiesare due to theoreticaluncertainties

Note

Present knowledge on the Unitarity Triangle

Without using CPViolation measurements

in B physics

8234γ

5.01α2sin

89.047.0β2sin

The comprehensive study of CP violation requires the angle measurements

3 ways to produce CP violation in the SM

Interference of 2 direct decay amplitudes DIRECT CP VIOLATION

Interference of 2 mixing amplitude T violation

Interference of a direct decay and a mixing induced decay amplitude

W

B+

K+

0b

us

uuu

gt,c,u

B+

b

u

W

0uu

K+su

00 :ex KBKB

Asym M1 M2 sin(s) sin(W)No major exp. difficulties … but ratesDifficult to extract CKM Phase ... except for some cases

Bd0

W+

-b

u

ddu

d

Bd0

b

d

b

t,c,u tc,u, +u

d

-du

b

d

b

t xd

-

c

Bd0

b

d

b

xd

-

c

t c ,u c u,

)BBBB( 0000

NN:ex2

B

B

1

)(4

Asym

Very small Asymmetry (<1%)Rates OK … but experimentaldifficulty to control systematics

0d

0d BB :ex

At (4S) Asym(t) sin(W)sin(mBt)Clean extraction of CKM phase … but penguin pollution in some cases Need tagging of initial B flavorat (4S) need Dt time measurement

Bd0

Mixing + decay

Mixing Direct CP

***Clean

*Limited by

syst. and theory

*Limited by stat.

and theory

**Limited by stat.

or theory

*Limited by stat.

and theory

**Clean but stat. very limited

**Clean but stat. very limited

Qualitative quideline for measuring the angles of the Unitarity Triangle

ATLAS

2006

BTEVBTEV

CLEO 3BBAABBARAR

2005

1999 2000

2001

BELLE1999

2000

The World Quest for CP Violation in the B SystemThe World Quest for CP Violation in the B System

Primary Goal :Primary Goal :Primary Goal :Primary Goal :1) Carry a comprehensive study of CP violation in the b quark system2) Test the consistency of the Standard Model in the CKM sector and probe the origin of CP violation

Main Parameters of the asymmetric e+e- colliders

Achieving the nominal parameters is one of the challenge !!!… but full success of the physics program requires

Factory Operation

PEPII KEKB

HER LER HER LER

Ebeam (GeV) 9.0 (9.0) 3.1 (3.1) 8.0 (8.0) 3.5 (3.5)

Ibeam (A) 0.75 (0.92) 2.1 (1.7) 1.1 (0.9) 2.6 (1.4)

Nbunch 1658 (830) 2700 (1224)

Lifetime (mn) 600 250 300 200

Luminosity (cm-2 s-1) 3x1033 (4.3x1033) 1034 (7.2x1033)

Nominal values(present achievements)

L=76.0fb-1

KEKBPEPII

Operation and Luminosity of KEKB and PEPII

Both KEKB and PEPII are working very well in factory mode

KEKB and PEPII will run at least until next summer

Samples ofFully-Reconstructed B Decays

Cabbibo-favored hadronic decays “Open Charm” decays e.g.

Charmonium Decays

e.g.

Semileptonic decays

e.g.

ducb

s)cc(b

1)(0 /a/ρπDB

K/JB

DB0

Flavor eigenstates for mixing and lifetime measurements

)(cb

Reconstruction of B final states

2

,1

2

2

nii

cmB p

Em

2,1

cm

nii

EEE

2 main variables to identify B

~21000 signalPurity: 85%

Neutral Neutral BB Mesons Mesons

BBAABBARARBBAABBARAR

Charged Charged BB Mesons Mesons

~20000 signalPurity: 85%

Measurements of

B0

J/KS

B0 K-

D

General requirements for studying CP violation

also jet charge, partial D ’s, ...

d

z

Needed information to measure CP violation

1) Identify a reconstructed B0 (ex: J/KS

2) Measure t12 z

3) Identify the flavor of B0 at t0 using 2nd B

(i.e. tagging)

t0 t1 t2

tmef dt sin2sin1

)(/

)(

CPCP0BP

or ,

with

149.0 psmd

S0 KB :ex J

<z>=260m at PEPII<z>=200m at KEKB

Start the clockAt (4S) Factories

Btag=B000tag BB

)7.02(sin

CP Violation in mixingDileptons allow to test whether

)Prob()Prob( 0000 BBBB

24

4

1

e4

/1

/1

)()(

)()()(

B

BTA

pq

pq

NN

NNt

AT = (0.5 1.2 1.4)%

*tdVtbV

*tdV tbV

b

b

t

t

d

d

0B0B

CKM3-

tdtb

tdtbcbcd

m

mG

2t

2c

12

10-1

VV

VVVV1mm

M2W

2t

sin

Im21Im

21

1 212

qp

43 101101 TA

CL%90at005.01e2

BB

BABAR : Measurement of sin2

CP-1

sin2=0.76±0.10 ±0.04 sin2=0.73±0.19 ±0.07

BBAABBARARBBAABBARAR

raw asymmetry

sin2=0.75±0.09 (stat) ±0.04 (syst))

NBN

B

NB+

NB

NBN

B

NB+

NB

sin21 = 0.82 0.12 (stat) 0.05 (sys)

BELLE : Measurement of sin2 (=sin2

1

1

sin2=0.78±0.08

Where do we stand ?

CP Violation established in the B sector

Measurements compatible with SM

H.Lacker et al.

At present, B Physics alone allows to establish a non flat UT and its orientation

With all available information,

8234

5012sin

8905902sin

γ

.α

..β

Essentially no change on the constraints for sin2 and

These measurements are nowof prime importance to probe the

CKM sector of the SM

CP asymmetry in D*+D*- and D*+D-

D*D*

Ntag = 76Purity = 80%

D*DNtag = 85Purity = 52%

BBAABBARARBBAABBARAR

56 fb-1

)]tmcos(C)tmsin(S1[4

e)t(f dfdf

)/t(

b d

d

Wu,c,t

B0

g c

gluonic penguins

b cd d

W

B0

tree diagram c

dc

d

D(*)+

D(*)-

D(*)+

D(*)-

Less clean than “golden modes”as penguins may interfere witha new weak phase

Further complications:

In D* D* , final states has in principle both CP+ and CP- contentSf is dilutedIn D* D , 2 interfering amplitudes AD*D and ADD* may have different magnitudes(note: if one uses HQET+factorization AD*D ADD* and SD*D = SDD* sin2)

Direct CP violation sinsins

Decay x mixing “sin2”

no s quarkinvolves

D*+D-

S+- = -0.43 1.41 0.20 C+- = 0.53 0.74 0.13 D*-D+

S-+ = 0.38 0.88 0.05 C-+ = 0.30 0.50 0.08

… Expect 10-fold increase in statistics over the next 4 years

BABAR : RBABAR : Rtt = 0.22 = 0.22 0.18 0.18 0.03 0.03 S S 0.56 x “sin2 0.56 x “sin2” ” ((neglecting penguins)

An angular analysis allows one to measures the CP odd width in D*D*

D*D*

S = -0.05 0.45 0.05 C = 0.12 0.30 0.05 BABARBABAR

No sensitivity yet for observing CP violation but …

Measurements of

C 0 Direct CP violationS = sin2eff sin2

need to relateasymmetry to

via model

Decay distributions f+(f-) when tag = B0(B0)

1

||1

||1

||1

)Im(2

22

2

2

2

ff

f

f

CS

C

S

For additional weak phase

Measurement of “sin2”

b d

d

Wu,c,t

B0

g u

gluonic penguins

b ud d

W

B0

tree diagram

u

du

d

+

-

+

-

)]tmcos(C)tmsin(S1[4

e)t(f dfdf

)/t(

i2f

)(i2f

f

f eeAA

pq

C 0, S = sin2

12

icb

iub

icb

iubi

eAeA

eAeAe

For single weak phase

BBNS

Charmless B decays needed

Results from B0 (with 55fb-1)

“sin2”= -0.01 ±0.37(stat) ±0.07 (syst))Other modes studiedas well e.g. B->

CL%90

0.480.54,- 0.07(syst) 0.29(stat)0.02- )C(

0.620.66,- 0.07(syst) 0.37(stat)0.01- )S(-

-

ππB0

~83 B+-

πKB0

~356 BK+-

Preliminary Results

(~83 candidates) before tag

“sin2”= -0.01 ±0.37(stat) ±0.07 (syst))

S = [-0.63,+0.60]

coscos

sinsin222

cbubcbub

cbub

AAAA

AAC

)22sin( penguinS

BBNS

To extract sin2 either :

Isospin analysis using B 0 and B0 00

or

requires using theory

CL%95

1.0.30, 0.09(syst) (stat)0.94 )C(

0.391.,- (syst) (stat)1.21- )S(0.25

0.31--

0.160.13-

0.380.27-

-

“sin2”= -1.21 +0.38-0.27

(stat) +0.16-0.13

(syst))

BELLE results on B0 (with

41.8fb-1)

Observe large difference in B0 and B0 ratesand times dependence

(73.513.8 candidates) before tag

Direct and mixing induced CP

Comments on B0

BABAR results compatible with factorization (BBNS …)

BELLE at ~1.4 from S2+C2 < 1 bound C large (may be first evidence of Direct CP violation in B system but requires - very large penguins P/T 1 ( should be seen soon) - large strong phase (not so compatible with BBNS)

Both results marginally compatible (C and S each at ~2

… definitely more statistics is needed, first Rendez Vous this summer

Direct CP Violation ?

sinsin

sinsin

No Evidence forDirect CP violation … yet!

~pure penguinmodes

Summary

The B factories KEKB and PEPII have started remarkably well with luminosity surpassing design values

The detector BABAR and BELLE are working well and have established CPviolation the the B meson sector

sin2=0.78±0.08BABAR + BELLE

not enough statistics to do the comprehensive study of CP violation yet… but near future prospects looks very promising

However, a lot remains to do : Measuring the other angles of the UT Direct CP violation still to be seen errors on T violation need to be reduced

Many other measurements on Vcb, Vub, Vtd to come as well as searching for supersymmetry in rare B decays (e.g. b->s …)

What ’s next ?

BABAR has already ~85 fb-1 (i.e. x1.3 the statistics presented this winter)and will continue until end June 2002 ( ~100 fb-1 on+off resonance).BELLE has very similar plans and goals (i.e ~ 100 fb-1 on+off this summer)

0S

0 KB

sssb DDB0

dccb

Increase statistics in Golden modes 12sin fb10008.0 for

12sin fb10008.0 for

Many other CP modes can potentially provide independent measurement of sin2

different quark processes various penguin contributions angular analyses for VV modes

New charmonium modes will added (e.g. cKs …)

*0 DD,DDB 0S

0S

0 K,KB

Perspectives for sin2 ?

Perspectives for sin2 ?

with increased statistics onlywith10025.0 1"2sin" for fba onlywith10025.0 1"2sin" for fba

should be observed and isospin analysis may start to be possible

Other modes such as should come into the game with similar sensitivities as

Perspectives for measuring D* decays to extract sin(2)

CPV in mixing/decay clean theoretically,

pure tree amplitudes – no penguin pollution …but time-dependent CP asymmetries at the few % level

D*K decays to extract interference with

(DCS) πDBπDB ** 00

Original construction by Gronau & Wiler +

Dunietz

CP00 fD,D

Both methods are Extremely challenging

experimentally!

22s

07.008.000

00

24.016.0)()(

)()(

KDBBrKDBBr

KDBBrKDBBrA

CPCP

CPCPCP

04.024.022.0

05.026.029.0

)()(

)()(00

00

KDBBrKDBBr

KDBBrKDBBrA

KDB 0 KDB 0

BABARBABAR

BELLEBELLE

BELLE (29 fb-1)

Mode B(x10-5)

GeVρ γ ρ

GeVπ γ(892)π

(1430)γ

(892)γ

(892)γ

inclusive γ

0.2)(7.15.6

0.2)(9.01.16.5

10.066.026.1

46.083.3

36.043.4

2.43.56.33

1.12.1

**

*2

0

*

0*0

0.54.5

KmKB

KmKB

KB

KB

KB

XB S

Radiative B decays Penguin loop for non-SM

particles Probe for new physics BELLEBELLE

<BaBar+Belle+PDG>

BELLEBELLE

Inclusive B Xs one energetic photon E> 2 GeV

Xs : one K or KS plus 1 to 4 pions

BABARBABAR

Electroweak Penguin decays

Very interesting to search for new physics possibly leading to large CP violation effect

In SM, Br is expectedin the (0.2-0.5)x10-6 range for Kllin the (0.8-2.2)x10-6 range for K*ll

New Ali et al. predictions are lower!

BELLE (29.1 fb-

1)BELLE (29.1 fb-

1)

Mode Yield Signif. B(x10-6) Theory

6.7-5.7μμ

2.38.4ee

1.9-1.0μμ

0.6-0.3μμ

2.3-1.4ee

0.6-0.3ee

9.197.24.11

2.100.3

0.38.2

99.08.45.9

1.51.25.5

2.16.2

1.58.4

9.43.4

9.21.2

*

13.039.015.032.0

7.31.3

7.30.3

*

7.20.2

S

S

XB

XB

KB

KB

KB

KB

CL%90at108.3)(B

10)26.094.1()(B

10)08.084.0()(B

6

611.174.0

631.025.0

K

K

K

B i.e.BB

625.021.0 10)09.075.0()(B

KB

B+ K+ +–

B0 KS +–

Combined

Electroweak Penguin decays (cont’d)

619.016.0 10)09.079.0(

)(B

BELLEBABAR

KBBABAR (54.6 fb-1)BABAR (54.6 fb-1)

CL)%90(101.2)(B

CL)%90(101.2)(B

CL)%90(103.3)(B

7

7

7

e

ee

BBB

NoteAlso :

Luminosity projections and prospects for KEKB and PEPII

Luminosity projection (baseline)

0

200

400

600

800

1000

1200

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Year

Inte

gra

ted

Lu

min

os

ity

(/f

b)

Luminosity

PEPIIPEPII

Upgrade toward 1035 under consideration

KEKBKEKB

KEKBKEKB

650 fb-1 in 2007

Similar studies going on for PEPII

CP Reach extrapolations at BABAR

Conclusion

CP Violation is now established in the B sector and sin2= 0.78 0.08… it is consistent so far with the prediction of the SM

The Challenge of the Asymmetric B Factories has been met.Both machines and detectors are operating beautifully, surpassingthe anticipated performance

Most results on B physics are more precise than the world averagei.e. the comprehensive study of the CKM sector has started

Still a lot of work ahead of us but very exciting time both for experimentalists and theorists for getting new ideas as it becomes possible to probe them now

with the hope that it will unravel inconsistencies of the SM andpoint toward new physics as CP in the SM is unable to account quantitatively for Baryon Asymmetry of the Universe