1. The Measurement of sin2β(eff) in Loop-Dominated B Decays with BABAR
Andreas Höcker
Laboratoire de l’Accélérateur Linéaire, Orsay
For the BABAR Collaboration
ICHEP 2004
August , 2004, Beijing, China
Preliminary analyses documented in BABAR-CONF-04/33, 04/25, 04/40, 04/19, 04/30
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

2. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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 ?
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
see, e.g., the instructive talk by Y. Grossman at LP’03: hep-ph/
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
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
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

3. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Confronting Loop Decays with Tree Dominance
decays are tree and penguin diagrams, with equal dominant weak phases
decays are pure “internal” and “flavor-singlet” penguin diagrams
High virtual mass scales involved: believed to be sensitive to New Physics
Both decays dominated by single weak phase
Tree:
Penguin:
New Physics? 3 ?
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

4. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Penguin Olympia
Naive (dimensional) uncertainties on sin2
One may identify golden, silver and bronze-plated s-penguin modes:
Gold
Color-suppressed tree
Silver
Color-suppressed tree
Bronze
Note that within QCD Factorization these uncertainties turn out to be much smaller !
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

5. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
All Results are
PRELIMINARY !
Definition of Time-dependent CP asymmetry observables:
CP observables
with:
~ –CPsin(2 )
and
~ 0
for b  ccs, sss
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

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

7. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Analysis of B 0   K 0
227106 B pairs
full background
continuum bkg
ML fit finds 114 ± 12 signal events
98 ± 18 signal events
Systematic errors dominated by
opposite-CP background
PDF modeling
Tag-side CP violation
combined fit :
sin2 0.9
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

8. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Analysis of B 0/+   K 0/+
227106 B pairs
B0KS
(statistical errors only)
Complementary penguin mode:
Significant direct CP violation would be hint for New Physics
B0KL
Fit finds 400 ± 23 signal events
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

9. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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):
Study  [K+K–] helicity angle distribution
and:
Average moments computed from sum of background-corrected signal weights, returned by ML fit (“sPlot” technique [Pivk-Le Diberder, physics/ ])
Isospin analysis (cross check) [Belle, PRD 69, (2004)]
(statistical error only)
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

10. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Analysis of B 0  K+K–K S (II)
Results from CP fit
Fit finds 452 ± 28 signal events (excluding  KS events)
Systematic errors dominated by
Fit bias
Tag-side CP Violation
ML fit:
use C=0:
sin2 0.7
CP content
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

11. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Analysis of B 0  ’ K S
227106 B pairs
Large statistics mode: , we exploit:
Reconstruct in multiple final states: ’   + –,  0  and     ,  + – 0 and KS  + – , 0 0
3.0
Fit finds 819 ± 38 events
No CPV found in control sample
ML fit :
sin2 3.0
Systematic errors dominated by: Fit bias (MC statistics)
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

12. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Analysis of B 0  f0 K S
209 106 B pairs
New, silver-plated s-penguin mode with
[BABAR, hep-ex/ ]
Requires thorough estimate of CP dilution due to interference in B0   + – KS Dalitz plot
Fit finds 152 ± 19 events
2.3
ML fit :
Systematic errors dominated by
Fit bias & interference with other modes
sin2 0.6
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

13. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Analysis of B 0   0 K S (I)
227 106 B pairs
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 (+2B)-constraint)
keep remaining “no-t ”events for direct CPV measurement
mass-constrained
Replace E and mES by: and
 reduced correlation, improved resolution (mmiss)
Fit finds 300 ± 23 events
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

14. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Analysis of B 0   0 K S (II)
~ SM
sPlot 1 2 3
physical limit
Systematic errors dominated by
Background tagging asymmetry
SVT alignment, vertexing
ML fit :
sin2 1.3
No bias in control sample decays without using J / -decay tracks for vertexing
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR

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

16. A. Höcker – sin2 in Loop-Dominated Decays with BABAR
Conclusion
BABAR has new sin2(eff) results for all s-penguin analyses, most using 227 106 B pairs
Introduced and observed new silver-plated s-penguin mode
Sophisticated vertexing allows time-dependent measurement of CPV in
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:
... and overall:
s-penguins
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR