Transcript 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 16 -

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 16 - 22, 2004, Beijing, China
[email protected]
ICHEP’04, Beijing, Aug 16-22, 2004
Preliminary analyses documented in BABAR-CONF-04/33,
A. Höcker – sin2 in Loop-Dominated Decays with BABAR
04/25, 04/40, 04/19, 04/30
1
The Quest for New Physics in B Decays
Since the successful and precise measurement of sin2β in b  ccs 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/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
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
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A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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Confronting Loop Decays with Tree Dominance
b  ccs decays are tree and penguin diagrams, with equal dominant weak phases
b  sss 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:
c
b

cb
V
W

Vcs
d
c J /
s
b  ccs
J / K
0
S ,L
b  sss
Penguin:
s
New Physics?
b
3
g, Z,

tb ts
VV
d
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 q
2 i 
     J / KS0,L e
  p K
K0
d
u, c , t
 q   VcbVcs
 J /  K 0     
S ,L
 p B  VcbVcs
s

K
0
S ,L
 q   VtbVts   q 
 K 0          ~ K 0 e 2i 
S ,L
S ,L
 p B  VtbVts   p K
s
K0
d
?
sin2 [charmonium]  sin2 [s-penguin]
A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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Penguin Olympia
Naive (dimensional)
uncertainties on sin2
One may identify golden, silver and bronze-plated s-penguin modes:
Gold
W
B
0
 VubVus ~  4Ruei

u
b
g
d
Silver
Color-suppressed tree
B
0
Bronze
B
K0
W
u

s
d
u
W

[CP ]
B
0
b
 ', f0

u
s
d
g
s
B
0
b
W
0
B
0
b
d
, K  K 
( 2 )
K0
~ 5%
[CP ]
 VtbVts ~  2

t
s
g
s
 ', f0
s
d
K0
d
 ,  ,
K0
s
s
d
W
K0
0
t
d
 VubVus ~  4Ruei
b
d
s
d
u
Color-suppressed tree
0
, K K

 VubVus ~  4Ruei
b
d
s
s
W
 VtbVts ~  2

( 2 (1 fqq /  ))
 VtbVts ~  2

t
g
s
d
K0
d
d
 0 ,  0 ,
Note that within QCD Factorization these uncertainties turn out to be much smaller !
ICHEP’04, Beijing, Aug 16-22, 2004
~ 10%
A. Höcker – sin2 in Loop-Dominated Decays with BABAR
( 2 /  )
~ 20%
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All Results are
PRELIMINARY !
(B (t )  fCP )  (B (t )  fCP )
AfCP (t ) 
(B 0 (t )  fCP )  (B 0 (t )  fCP )
0
0
 SfCP sin( md t )  CfCP cos( md t )
with:
~ –CPsin(2 )
ICHEP’04, Beijing, Aug 16-22, 2004
and
~0
CP observables
Definition of Time-dependent CP asymmetry observables:
SfCP 
CfCP 
2Im  fCP 
2
1  fCP
1  fCP
2
1  fCP
2
for b  ccs, sss
A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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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
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A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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Analysis of B 0   K 0
B0  KS0  K K   
B0  KL0
227106 B pairs

 KL0
 K 0
S

full background
continuum bkg
combined fit :
ML fit finds 114 ± 12 signal events
98 ± 18 signal events
Systematic errors dominated by
SK 0  0.50  0.25
 0.07
 0.04
CK 0  0.00  0.23  0.05
sin2 [cc] @ 0.9
ICHEP’04, Beijing, Aug 16-22, 2004
opposite-CP background
PDF modeling
Tag-side CP violation
A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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Analysis of B 0/+   K 0/+
B0KS
SK 0  0.29  0.31
S
0
Btag
K  1
0
Btag
0
S
B0KL
(statistical
errors only)
227106 B pairs
Complementary penguin mode:
B  K   K K K 
Significant direct CP violation would
be hint for New Physics
SK 0  1.05  0.51
L
0
Btag
K  1
0
L
0
Btag
Fit finds 400 ± 23 signal events
AK   0.054  0.056  0.012
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A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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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
| AB0 K K K 0 (cos ) |2 
S
and:

P  P (cos )
0,1,2
As2  2 P0  5 / 2 P2
Ap2  5 / 2 P2
Average moments computed from sum of
background-corrected signal weights, returned by
ML fit (“sPlot” technique [Pivk-Le Diberder, physics/0402083])
As2
fCP -even  2
 0.89  0.08  0.06
As  Ap2
Isospin analysis (cross check) [Belle, PRD 69, 012001 (2004)]
fCP -even
2(B   K KS0KS0 )

 0.75  0.11
(B0  K K K 0 )
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(statistical error only)
A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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Analysis of B 0  K+K–K S (II)
Results from CP fit
0
Btag
0
Btag
Asymmetry
Fit finds 452 ± 28 signal events
ML fit:
(excluding  KS events)
SK K K 0  0.42  0.17  0.04
S
CK K K 0  0.10  0.14  0.06
use C=0:
S
Systematic errors dominated by
Fit bias
Tag-side CP Violation
sin2 ~ SK K K 0 /(2fCP -even  1)  0.55  0.22  0.04  0.11
S


CP content
ICHEP’04, Beijing, Aug 16-22, 2004
A. Höcker – sin2 in Loop-Dominated Decays with BABAR
sin2 [cc] @ 0.7
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Analysis of B 0  ’ K S
227106 B pairs
 KS0 ) ~ 14.9  106
Large statistics mode: BR(B0  K 0 ) ~ 65.2 106, we exploit: BR(B0  rec
Reconstruct in multiple final states: ’   + –,  0  and     ,  + – 0 and KS  + – , 0 0
B0  KS0
0
Btag
3.0
0
Btag
Fit finds 819 ± 38 events
S K 0
ML fit :
S
S K 0  0.27  0.14  0.03
S
C K 0  0.21  0.10  0.03
S
No CPV
found in
B   K 
control
sample
Asymmetry
sin2 [cc] @ 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
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Analysis of B 0  f0 K S
209 106 B pairs
New, silver-plated s-penguin mode with BR(B0  f0 (980)KS0 ) ~ 6.0 106
[BABAR, hep-ex/0406040]
Requires thorough estimate of CP dilution due to interference in B0   + – KS Dalitz plot
0
Btag
0
Btag
ML fit :
Fit finds 152 ± 19 events
Sf K 0  0.95
0 S
 0.32
 0.23
 0.10
Cf K 0  0.24  0.31  0.15
0 S
sin2 [cc] @ 0.6
ICHEP’04, Beijing, Aug 16-22, 2004
Asymmetry
CPV @ 2.3
Systematic errors dominated by
Fit bias & interference with other modes
A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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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 (4S)  B0B0 decay tree (use Ebeam, IP (+2B)-constraint)
keep remaining “no-t ”events for direct CPV measurement
mass-constrained
Replace E and mES by: mmiss  |qee  qˆB K 0 0 |  2mES  mBPDG and mrec  |qB K 0 0 |  E  mBPDG
S
S
 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
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Analysis of B 0   0 K S (II)
0
Btag
S 0K 0
~ SM
S
sPlot

1
0
tag
B
2
3
Asymmetry
physical limit
C 0K 0
ML fit :
S
S 0K 0  0.35
S
 0.30
 0.33
 0.04
C 0K 0  0.06  0.18  0.06
S
sin2 [cc] @ 1.3
Systematic errors dominated by
Background tagging asymmetry (C 0K 0 )
S
SVT alignment, vertexing (S 0K 0 )
S
No bias in B0  J / KS0 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
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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
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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 B0  f0 (980)KS0
Sophisticated vertexing allows time-dependent measurement of CPV in B0   0KS0
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:
B0  K 0
B 0  K  K K 0
... and overall:
ICHEP’04, Beijing, Aug 16-22, 2004
B0  K 0
B0  f0K 0
B0   0K 0
s-penguins
A. Höcker – sin2 in Loop-Dominated Decays with BABAR
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