sin2: Status & Perspectives

Gerhard RavenNIKHEF & VU Amsterdam

sin 2 0.731 0.055WA

12 , sin20.790.11 S BJKBX

BaBar

CP from Interference of Mixing and Decay

0 0

0 0

( ( ) ) ( ( ) )( )

( ( ) ) ( ( ) )

cos( ) sin( )

CP

CP CP

CP CPphys physf

CP CPphys phys

f d f d

B t f B t fa t

B t f B t f

C m t S m t

Time-dependent CP asymmetry:

CP violation results from interference between decays with and without mixing

CP violation results from interference between decays with and without mixing

2= | |

CP

CP

CP

CP

CP

ff

f

i

f

Aqλ

p A

λ e

decaymixing

2f

2f

f||1

||1C

CP

CPCP

2f

ff

||1

Im2S

CP

CPCP

0B

0B

CPf

mixin

g

decay

CPfA

CPfA

decay

0 0 0 0

* * *

* * *

decay mixing mixing

S

S

S

J K tb td cb cs cs cdJ K

J K tb td cb cs cs cd

B B K K

V V V V V Vq A

p A V V V V V V

Theoretically clean way (~1%) to measure sin2

0 0, ,

0,

/ /

/

sin2

0S L S L

S L

J K J K

J K

S

C

BJ/KS,L: dominated by single decay amplitude

Ingredients of the Measurements

B-Flavor Tagging

Exclusive B Meson

Reconstruction

PEP-2 (SLAC)

Vertexing &Time DifferenceDetermination

fflav: determine t resolution, mistag rates w, (md, B, …) fCP: measure CP asymmetries

Available Samplesbefore tagging and vertexing cuts

B decays to flavor-specific final states

B decays to CP-eigenstates with charmonium

angular analysis (not shown)

Add Belle D*lnu here 0B D

2 222

,2 cos

CMS CMS CMS CMSCMS CMSB B D B DD B D

M E E p p p p

99999999999999999999999999999999999999999999999999999999

Belle

21

BaBar

Flavour TaggingMistag rates measuredusing control samples

Babar:– D(*)//a1

– Simultaneous fit with CP sample

• Errors due to finite control sample size automatically included in statistical error

Belle:– D*lv– Separate fit,

propagate numbers to CP fit

Belle: rank individual tags based onexpected performance in 6 groups

BaBar: rank according to ‘physics process’(eg. Lepton tags, Kaon tags,…) withperformance cuts (eg. Kaon I and Kaon II)Drop low performance tags, end up with 4 groups

sin 2 1 Q 2 28.1 0.7%1 2

28.6 0.6%

(BaBar)

(Belle) i iiQ w

Doubly CKM suppressed decays on tag side1. Many BDX modes have, at O(10-4), intrinsic “mistagging” due to bu

transitions. Effect usually assumed to be • Small• Accounted for by measured mistag rates

2. On reco-side this bu interference can be used for sin(2 + ) measurement. Induces time-dependent effects of order |VubVcd/VcbVud|= 0.02

Lepton tags unaffected, but eg. Kaon based tags are

•For BaBar: Qlep ~0.1, Qnonlep ~0.2

Small effect on sin(2), larger on ||; last BaBar result:

DCSD(sin2)= 0.008 (cmp to total syst: 0.034)

DCSD(||) = 0.024 (cmp to total syst: 0.030)

0 2 sin sin

sin 2 1 cos cos 2 cos(2 ) sin(2 )sin(2 )sin 2

S

S

J K

J K

C r

rS

bu interference for tag-side B induces time-dependent effect, just like reco-side and thus not fully accounted for in measured mistag rates

Long, Baak, Cahn, Kirkby

hep-ex/0303030, submitted to PRD

B0

B0

3. (4s) B0 B0 system is antisymmetric in two B mesons

4. System evolves coherently in time

Results

BelleBaBar

1

sin 2 0.741 0.067 0.033

sin 2 0.719 0.074 0.035

(BaBar)

(Belle)

sin 2 0.755 0.074 sin 2 0.723 0.158

1sin 2 0.78 0.17

1sin 2 0.71 0.09

PRL 89 (2002) 201802PRD 66 (2002) 071102

sin 2 0.731 0.055 (CL = 0.84)WA

Note that the experiments also agree on color codes for B and B tags

N(BB)= 88 106N(BB)= 85 106

Belle/KEK-B

Extrapolation: Luminosity

SVD2 installation

Belle/KEK-BBoth experiments expect ~500/fb by 2006

BaBar/PEP II

Extrapolation: Some History…a) “Osaka 2000” measurement. (hep-ex/0008048).

• Only J/KS and (2s) KS.

b) 1st Paper (PRL 86 (2001) 2515).• Added J/KL.• Simultaneous sin2 and mixing

fit.

c) 2nd Paper (PRL 87 (2001) 091801).• Added J/K*0 and c KS. • Better vertexing.• Better SVT alignment and

higher KS efficiency for new data.

d) Winter 2002 (hep-ex/0203007).• Improved event selection.• Reprocessed 1st 20 fb-1.

e) 3rd Paper (PRL 89 (2002) 201802 )• Improved flavor tagging.• One more CP mode: cKS.

a

b

c

de

So far seem to do better than extrapolations predict

Systematic

Statistical

sin

2

un

cert

ain

ties BaBar

Extrapolation: BelleExpected errors in ACP’s

KEKB

PEPII

Next B factory

Goals for July 2005:315 /fbStat. error ~0.04Syst. error ~0.02

Goals for July 2007:1000 /fbStat. error ~0.02Syst. error ~0.01

Will require a lot of hard workto get there!

Extrapolation: BaBar

Currentanalysis

Clean modesOnly lepton tags

Current analysis Clean modes, Lep. tag

Integrated L (fb-1) 81 500 2000 81 500 2000

Statistical error 0.067 0.028 0.013 0.113 0.047 0.022

Systematic error 0.034 0.024 0.022 0.025 0.015 0.012

Total error 0.075 0.037 0.026 0.116 0.049 0.025

“Probably somewhat conservative…”

The assumptions…

•Mixing

•Decay

Back to basics: Flavour Mixing

12

2

212arg arg c

b

m

mM

O

2 2

2 22 20

2

12

1 3 1

2 /b b

W tt W

m

m S m mM

m

m

O

121

12 121

2

22 12

2

1 sin arg argMM M

q

p

O

Eigenstates:

With mass & lifetime differences:

0 0,H LB p B q B 12

1

* *12

212

2

2

iq

ip

M

M

, with

12

122

12

1

2 0

2

H L

H L

M

MM

m m m

Assumptions made:1. CPT conserved

2. no CP in mixing

3. =0

2

1 0CP

qa

p

11 11* *

22 2

12

12

2

2

1

122 2

M

M

Mi iM

H M Γ

Effective Hamiltonian:

Note: if CPT and DG=0 => q/p is pure phase

2

12 12 12 122 2 2

02i i i

M M M

iMz

11 22

11 22

M M M

CP in mixing: experiment

sgn / 0.08 0.037 0.018

1.029 0.035 0.034

0.014 0.035 0.034

0.038 0.029 0.025

CP

CP CP

q p

z

z

•Measure aSL using dileptons aSL=0.51.2(stat)1.4(syst)

•New analysis:•Simultaneous fit to time-dependence of both fully reconstructed CP and flavour eigenstates, tagged and untagged•Include

•Detector charge asymmetries•Doubly-CKM suppressed decays

Started testing the assumptions that1. CPT is conserved2. is negligible3. q/p is a pure phase

Nothing unexpected seen, will need MUCHmore data to approach SM prediction

preliminary

PRL 88 (2002) 231808

* * * *t c ucb cs tb ts cb cs ub usB J K V V T V V P V V P V V P A

Back to basics: CP in decayb

d

d

W cc

s

0B /J

0K

0K0Bb

dW

s

d

c

cg

u,c,t

/J

* *

2 small

c t u tcb cs ub usB J K V V T P P V V P P

A Leading penguin contribution has same weak phase as treeExpect very little direct CP

Phys. Rev. D-RC 65 (2001) (20/fb)0.003 0.030 0.004 BaBar

0.042 0.020 0.017 Belle

J K

J K

A

A KEK Preprint 2002-9 (29/fb))

• Experiment: Look for direct CP in J/K+

J K

N J K N J K

N J K N J K

A

BaBar

*04

*04

cos , e 1 +

, e 1 s o- c

tunmixed

tmixe

d

dd

m t

m

f J K t

f t tJ K

Are (sin2)J/Ks and (sin2)J/KL the same?

Need K0—K0 bar mixing for interference in J/ KS and J/ KL

CP violation in K0—K0 bar mixing: negligible

0 *0 0 *0

*0 *00 0

0.22 0.028 0.016

0.017 0.026 0.016

B J K B J K

B J K B J K

b

d

d

W cc

s

0B /J

u,c,t0K 0Ksds

d

Following Grossman, Kagan & LigetiPhys. Lett. B538 (2002) 327

Very much consistent with SM expectation of 0

BaBar

Measure “wrong flavour” amplitude in BJ/ K*0(K+-)

?d

cc

s 00 K,K

/Jb

d0B

*04

*04

cos

c

, e 1 + +

, e 1 - -

s

os sin

indt

unmixed

tmix d

d

ded

S m tCf J K t

f J K t

m t

tt mm SC

0 *

0 *

/

/

A B J Kqλ

p A B J K

2

2

1 | λ |

1 | λ |C

2

2Im λ

1 | λ |S

For B J/K*0(K-+) : CC, S S,

Other Modes

* 0SB J K K

SB KSB K

0B J

B D D

B D D B D D

Angular analysis, cos(2)

Color+Cabibbo suppressed tree + penguin

b s penguinb s penguin + CKM suppressed tree

bd Cabibbo suppressed tree + penguin, angular analysis

Cabibbo suppressed tree + non-CP eigenstate

O 1D: Treat R as dilution

2D: Use tr

4D: Full angular analysis

J/K*(KS0) and cos(2)Vector-Vector mode; Angular components:

• A|| ,A0 : CP = +1

• A : CP = -1 (define R = |A|2 ) Simplest method:

CP asymmetry diluted by D = (1 - 2R)

R = (16.0 ± 3.2 ± 1.4) % BaBar, PRL87 (2001) 241801 R = (19 ± 2 ± 3) % Belle, PLB538 (2002) 11-20

, , cos 2 cos 2

0 0

sin

0, , 0

0, , cos

, ,

0

4

, ,

cos1

2 sin(2 ) cos(2 ) si, n

, ,

,BB t

A q m tde

d td q A

A

m tA

99999999999999

99999999999999

99999999999999

99999999999999 J C

S S

Full angular distribution is given by:

So at first sight should be able to determine cos(2) and resolve someof the ambiguities in Unfortunately there is an ambiguity:

sin 2

cos 2

cos 2cos 2±0.7 (syst)±0.7 (syst)

BaBarBelle

BJ/0

In the absence of penguins, S=-sin(2) and C=0

b

d

d

W cc

d

0B /J

00B

b

dW

d

d

c

cg

u,c,t

/J

0

penguin: competing weak phase? tree: color- and Cabibbo-suppressed

hep-ex/0207058

hep-ex/0207098

Nsig=407

Penguin Modes: B KS

• Same CKM factors enter as J/KS.– u-penguin CKM suppressed by

~0.02.

• Unlike J/KS, the leading and u-penguin amplitudes are both penguins.

• Can use SU(3) related modes + and K*K+ to experimentally bound u-penguin amplitude.

– Grossman et al, hep-ph/9708305.

• Current estimate of SM “pollution” on the assumption

sin 2SKS is <5 %

Bb

d,u

W

ss

sg

Kd,u

bW

s

s

sg

u,c,t

Kd,u d,u

Binternal penguin

flavor-singlet penguin

BaBar

Belle

PRD 67, 031102(R) (2003)

Penguin Modes: B’KS

• Very similar to KS except for one additional complication – a tree-level bu contribution.

• London and Soni estimate the relative size of the bu tree to be |T/P|<0.02 (hep-ph/9704277)

• Beneke and Neubert estimate |T/P| (8 3)%

(hep-ph/0210085) • Rough estimate for SM pollution

is same as KS although this is probably somewhat less conservative.

PRD 67, 031102(R) (2003)

Belle

Belle BaBar

Penguin Modes: -CPS=sin(2) ?

’Ks

BaBar 0.02 0.34 0.03Belle 0.71 0.37 (+0.05)Ave 0.34 0.25

Ks

BaBar –0.19 (+0.52) 0.09Belle –0.73 0.64 0.22Ave –0.39 0.41

K+K-Ks non-resonantBelle 0.49 0.43 0.11 (+0.33)

’

–0.00

–0.06

–0.50

“bs penguin” average

Babar and Belle 0.18 0.20

About 2.5 below golden modes!

2/Ndof = 4.8 / 4 Caveat: averaging KS and ’KS assumes the b->u tree contribution in ’KS is negligible

Penguin Modes: C = 0 ?

’Ks

BaBar 0.10 0.22 0.03Belle –0.26 0.22 0.03Ave –0.08 0.16

Ks

BaBar –0.80 0.38 0.12Belle 0.56 0.41 0.16Ave –0.19 0.30

K+K-Ks non-resonantBelle 0.40 0.33 0.10 (+0.26)

“bs penguin” average “C”

Babar and Belle –0.03 0.13

Tree vs. Penguin: B D*+D-

b

d d

Wccd )(D

)(D0B0B

t,c,ub

dd

W

d

)(D

c

cg

)(D

Cabibbo-suppressed tree b d penguin

Gronau PRL 63, 1451 (’89) PLB 233, 479 (’89)

0.03 0.11 0.05D D D D

D D D D

N N

N N

A

0.24 0.69 0.12

0.22 0.37 0.10

0.82 0.75 0.14

0.47 0.40 0.12

S

C

S

C

PRL 89, 122001 (2002)

If penguins negligible, C=0, S=-sin(2)

BaBar

Note: not a CP eigenstate

D D

D D

Belle

BaBar

B D*D*

* *

* *

0.31 0.43 0.13

0.98 0.25 0.13

D D

D D

Mostly CP-even

Belle Belle

0.07 0.06 0.03 (BaBar)

close to zero (Belle)

R

R

BaBar

SummarySee also http://www.slac.stanford.edu/xorg/hfag/triangle/winter2003/index.shtml

Thanks to: Riccardo Faccini Yoshi Sakai Owen Long Gautier Hamel de Monchenault Andreas Hoecker

•Time dependent CP fits @ B factories have reached maturity•sin(2) measurement with charmonium KS,L well established,•Starting to explore other (rare) modes, but

…need more data!

sin 2 effS 2 21 1C

Summary

See also http://www.slac.stanford.edu/xorg/hfag/triangle/winter2003/index.shtml

Thanks to: Riccardo FacciniYoshi SakaiOwen LongGautier Hamel de MonchenaultAndreas Hoecker

•Time dependent CP fits @ B factories have reached maturity

•sin(2) measurement with charmonium well established,

•Consistent with constraint from indirect measurement•no longer limiting factor on CKM analysis

•Starting to explore other (rare) modes, but

•…need more data!

BACKUP SLIDES

Details: from z to ttagrec

rec tag,rec ,tag

rec tagwhere and are in diff erent f rames

Bz z

zzt t t m

p p

t t

Proper time difference:

* * * *rec rec tag rec rec rec rec tag

Since one is f ully reconstructed and two mesons are correlated:( ) cos ( )

B Bz c t t c t t

Boost Approximation *,rec ,tag (4 ),Neglect , take : B z z S zp p p

zp t

c

rec tag

rec tag

Do not know ( ), but can compute average event-by-event:

Bt

t t t

t t t

Improved Boost Approximation *r

*rec

ec

Since cos 0, z

tc

0.2% effect

Average B Approximation 0* * * *rec rec rec reccos ( | |)

Bz c t c t

1. Improves resolution by 5% in quadrature2. If not used, resolution depends on |t|

Penguin Modes: the data…

BaBarhep-ex/0207070

Bellehep-ex/0212062Submitted to PRD

Yields (BaBar)BaBar

Tagging Performance1

(sin 2 )Q

0 0l B l B 0 0K B K B

Tagging PerformanceCategory Efficiency () Mistag Fr. () Mistag Q=(1-2)2

Lepton 9.1 0.2 3.3 0.6 -1.4 1.1 7.9 0.3

Kaon I 16.7 0.2 9.9 0.7 -1.1 1.1 10.7 0.4

Kaon II 19.8 0.3 20.9 0.8 -4.2 1.1 6.7 0.4

Inclusive 20.0 0.3 31.6 0.9 -2.0 1.2 2.7 0.3

Total 65.6 0.5 28.1 0.7

Control Samples

No asymmetry observed as expected

Systematic Errors for sin(2b)

Source sin2

CP and Mix BG 0.017

Klong BG 0.015

t meas. and RF 0.017

Signal Dilutions 0.012

Fit bias correction 0.010

B lifetime 0.004

md 0.003

Total 0.033

Total from winter 2002 result (56 fb-1) was 0.035

Largest source comes from backgrounds• CP of Argus BG is zero in default fit. Attempt

to fit for it in SB. Difference is systematic (very conservative).

• Klong BG contributions• Composition of J/X BG : 0.007• Shape/reslution of E : 0.007

Some improvements over last iteration• Switched from PDG 2000 to PDG 2002 for B

lifetime and md. PDG uncertainties down by x2 (thanks to us). Both were 0.010 last time.

• Peaking BG now split by mode. J/Ks has the lowest (0.3%, others >1.2%). Was 0.013, now 0.007.

• MC bias correction (or MC statistics). Used x7 more MC this time. We understand part of the bias. Was 0.014, now 0.010.

t reconstruction Reconstruct Brec vertex from

charged Brec daughters

Determine BTag vertex from All charged tracks

not in Brec

Constrain with Brec vertex, beam spot, and (4S) momentum

Remove high 2 tracks (to reject charm decays)

High efficiency: 95% Average z resolution ~ 180 m (dominated

by BTag) (<|z|> ~ 260 m)

t resolution function measured from data

Beam spot

Interaction Point

BREC Vertex

BREC daughters

BREC direction

BTAG direction

TAG Vertex

TAG tracks, V0s

z

Lepton tag only

(cc)KS with lepton tag

Ntagged = 220

Purity = 98%

Mistag fraction 3.3%

t 20% better than other tag categories

sin2 = 0.79 0.11

Belle b->s penguin