Andreas Höcker Laboratoire de l’Accélérateur Linéaire, Orsay

ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 1

The Measurement of sin2β(eff) in Loop-Dominated B

Decays with BABAR Andreas Höcker

Laboratoire de l’Accélérateur Linéaire, Orsay

ICHEP 2004

August 16 - 22, 2004, Beijing, China

For the BABAR Collaboration

Preliminary analyses documented in upcoming BABAR-CONF-04/33, 04/25, 04/40, 04/19, 04/30

[email protected]


The Quest for New Physics in B Decays

Since the successful and precise measurement of sin2β in decays (in perfect agreement with the SM), considerable effort at B Factories towards the search for specific signs of New Physics (NP)…. WHY ?

b ccs

The gauge hierarchy Problem (Higgs sector, scale ~ 1 TeV)

Baryogenesis (CKM CPV too small)

The strong CP Problem (why is ~ 0 ?)

Grand Unification of the gauge couplings

... many more

Note that: if NP contributes significantly to CPV in loop decays, we naturally expect it to be different among the modes averaging only useful in case of SM

see, e.g., the instructive talk by Y. Grossman at LP’03: hep-ph/0310229

Conflict between limits from flavor physics 1 TeV (e.g., K0, D0, B0 mixing), and NP scale (1 TeV) NP cannot have a generic flavor structure

Requires flavor suppression and/or generic suppression and/or alignment


Confronting Loop Decays with Tree Dominance

High virtual mass scales involved: believed to be sensitive to New Physics

decays are tree and penguin diagrams, with equal dominant weak phases

decays are pure “internal” and “flavor-singlet” penguin diagrams

Both decays dominated by single weak phaseBoth decays dominated by single weak phase

b s

, ,u c t, ,g Z

tb tsV V

Penguin:

s

dd

s

Tree:

b

dd

W cbV

csV

0K

c /J

s0K

New Physics? 3

0 0 0, , ,

2

/ / /S L S L S L

icb csJ K J K J K

cb csB K

V Vq qe

p V V p

c

0 0 0, , ,

2~S L S L S L

itb tsK K K

tb tsB K

V Vq qe

p V V p

b ccs

b sss

b ccs

b sss

?[charmonium]sin2 [ -penguin]sin2 s


Bro

nze

Sil

ver

Go

ld b

dg

u0B

d

ss

[ ],

CPK K

W

Penguin Olympia

One may identify golden, silver and bronze-plated s-penguin modes:

4~ iub us uV V R e

b

dg

t0B

d

ss

s

W 4~ i

ub us uV V R e2~tb tsV V

W b

d

0B

d

uu

0', f

s 0K

0K 0K

0', f

0K

Color-suppressed tree

s

b

dg

t

d

ss

s

W

0B

2~tb tsV V

b

dg

t0B

d

ds

d

W 4~ i

ub us uV V R e2~tb tsV V

W b

d

0B

d

uu 0 0, ,

s 0K0 0, ,

0K

Naive (dimensional) uncertainties on sin2

2( )

~ 5%

~ 10%

2( / )

~ 20%

Note that within QCD Factorization these uncertainties are much smaller !

[ ],

CPK K

2( (1 / ))qqf

Color-suppressed tree


All Results areAll Results are

PRELIMINARYPRELIMINARY !

Definition of Time-dependent CP asymmetry observables:

0 0

0 0

( ( ) ) ( ( ) )( )

( ( ) ) ( ( ) )

sin( ) cos( )CP

P

C

C

P

CP CPf

CP P

d df

C

f

B t f B t fA t

B t f B t f

m t C m tS

~ 0~ –CPsin(2 ) for b ccs, sssandwith:

2

2

2

2Im

1

1

1

CP

CP

CP

CP

CP

CP

f

f

f

f

f

f

S

C

CP

obs

erva

bles


Highlights on Common Analysis Techniques

Strong DIRC Particle ID to separate pions from kaons

Event shape monomials (L0,L2), and B kinematics optimally combined in Multivariate Analyzer [MVA] (Neural Network (NN) or Fisher Discriminant)

New NN-based B-flavor tagging with “Q” up to 30.6 %

Unbinned maximum-likelihood fit using beam-energy-substituted B mass (mES), B-energy difference (E), the resonance mass and decay angle, the MVA, and t

Likelihood components are signal (correctly and misreconstructed), continuum background, charmed and charmless B-related backgrounds; as many likelihood-model parameters as possible are determined simultaneously from the fit to reduce systematic errors

Tagging-performance parameters and t resolution parameters determined simultaneously from fit to fully reconstructed B decays to charm

BABAR - DIRC


Analysis of B 0 K

0

0 0LB K0 0

SB K K K

ML fit finds 114 ± 12 signal events

227106 B pairs

98 ± 18 signal events

full backgroundcontinuum bkg

0 0L SK K

com

bine

d fit

:

0

0

0.07 0.040.50 0.25

0.00 0.23 0.05

K

K

S

C

Systematic errors dominated by

opposite-CP background

PDF modeling

Tag-side CP violationsin2 [cc] @ 0.9


Analysis of B 0/+ K

0/+

B0KSB0KS

B0KLB0KL 0 1.05 0.51

LKS

0 0.29 0.31SK

S

0tagB

0tagB

0tagB

0tagB

(statistical errors only)

B K K K K

Complementary penguin mode:

Fit finds 400 ± 23 signal events

0.054 0.056 0.012K

A

Significant direct CP violation would be hint for New Physics

227106 B pairs

0 1LK

0 1SK


Analysis of B 0 K+K–K S (I) 227 106 B pairs

Excluding : dominant contribution (85%) of inclusive BR much more statistics than KS

Unknown a priori CP content: CP-even fraction must be determined experimentally

Angular moments analysis (main result):

0 0

-even 0 0

2 ( )0.75 0.11

( )S S

CP

B K K Kf

B K K K

(statistical error only)

0 0

2

0,1,2

| (cos ) | (cos )SB K K K

A PP

20 22 5 / 2sA P P and:

Study [K+K–] helicity angle distribution

Average moments computed from sum of background-corrected signal weights, returned by ML fit (“sPlot” technique [Pivk-Le Diberder, physics/0402083])

Isospin analysis (cross check) [Belle, PRD 69, 012001 (2004)]

2

-even 2 20.89 0.08 0.06s

CPs p

Af

A A

225 / 2pA P


Analysis of B 0 K+K–K S (II)

Fit finds 452 ± 28 signal events (excluding KS events)

Results from CP fit

ML

fit:

0

0

0.42 0.17 0.04

0.10 0.14 0.06S

S

K K K

K K K

S

C


Fit bias

Tag-side CP Violation

0 -even~ /(2 1s ) 0.55 0.22 0.04 0.1in2 1S

CK PK KfS

CP content

0tagB

0tagB

Asymmetry

sin2 [cc] @ 0.7

use

C=

0:


No CPV found in

control sample

Analysis of B 0 ’ K S

Large statistics mode: , we exploit: 0 0 6BR( ) ~ 65.2 10B K

Reconstruct in multiple final states: ’ +

–, 0

and , +

– 0 and KS

+ – ,

0 0

0 0 6recBR( ) ~ 14.9 10SB K

0tagB

0tagB

Asymmetry

B K

0 0SB K

Fit finds 819 ± 38 events

ML

fit :

0

0

0.10.27 0.034

0.100.21 0.03S

S

K

K

S

C

Systematic errors dominated by: Fit bias (MC statistics)

227106 B pairs

sin2 [cc] @ 3.0

0SK

S

3.0


Analysis of B 0 f0 K S

New, silver-plated s-penguin mode with 0 0 60BR( (980) ) ~ 6.0 10SB f K

209 106 B pairs

[BABAR, hep-ex/0406040]

Requires thorough estimate of CP dilution due to interference in B0 +

– KS Dalitz plot

ML

fit :

00

00

0.32 0.230.95 0.10

0.24 0.31 0.15S

S

f K

f K

S

C


Fit bias & interference with other modes

CPV @ 2.3


0tagB

0tagB

Asymmetry

sin2 [cc] @ 0.6


Analysis of B 0 0 K S (I)

Challenging vertexing (t ) due to lifetime of KS :

require at least 4 SVT hits (~60% of events) for t measurement

determine t from global fit to entire decay tree (use Ebeam, IP (+2B)-constraint)

keep remaining “no-t ”events for direct CPV measurement

227 106 B pairs

0 0(4 )S B B

Replace E and mES by: and

reduced correlation, improved resolution (mmiss)

0 0

PDGEmi s Ss | | 2ˆ

SB K Be eqqm m m

mass-constrained

0 0

Drec

P G| |S

BB Km q E m



Analysis of B 0 0 K S (II)

0tagB

0tagB

Asymmetry

sPlot

ML

fit :

0 0

0 0

0.30 0.330.35 0.04

0.06 0.18 0.06S

S

K

K

S

C


Background tagging asymmetry

SVT alignment, vertexing

No bias in control sample decays without using J / -decay tracks for vertexing0 0/ SB J K

0 0( )SK

C

0 0( )SK

S

~ SM

physical limit

12

3

0 0SK

C

0 0SK

S

sin2 [cc] @ 1.3


sin2 (and related direct-CP ) Results from BABAR

s-penguin average at 2.7 from sin2[cc] (BABAR only)

no indication for direct CP violation


Conclusion

BABAR has new sin2(eff) results for all s-penguin analyses, most using 227 106 B pairs

The significant decrease in the statistical errors begins to provide precision measurements of CP violation in loop processes

The “Stamodometer” indicates for the different modes:

0 0B K0 0B K 0 0B K K K 0 00B f K 0 0 0B K

s-penguins

Introduced and observed new silver-plated s-penguin mode 0 00(980) SB f K

Sophisticated vertexing allows time-dependent measurement of CPV in 0 0 0SB K

... and overall:

Documents

Andreas Höcker Laboratoire de l’Accélérateur Linéaire, Orsay