Andreas Höcker Laboratoire de l’Accélérateur Linéaire, Orsay
description
Transcript of 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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 2
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 3
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 4
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 5
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 6
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 7
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 8
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 9
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 10
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
Systematic errors dominated by
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:
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 11
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 12
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
Systematic errors dominated by
Fit bias & interference with other modes
CPV @ 2.3
Fit finds 152 ± 19 events
0tagB
0tagB
Asymmetry
sin2 [cc] @ 0.6
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 13
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
Fit finds 300 ± 23 events
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 14
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
Systematic errors dominated by
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
ICHEP’04, Beijing, Aug 16-22, 2004 A. Höcker – sin2 in Loop-Dominated Decays with BABAR 15
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
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: