1. Measurements of g and sin(2b+g ) in BaBar
BaBar (pictures) and title
Gianluca Cavoto
Princeton University
Università di Roma ‘La Sapienza’
On behalf of the
BaBar Collaboration
ICHEP'04
32nd International Conference on High Energy Physics
Gianluca Cavoto

2. Angle g of the Unitarity Triangle
Measure relative phase between Vub and Vcb
Process mediated by both b  c and b  u amplitudes
Results (all preliminary)
g from direct CP asymmetry
sin(2b+g) time dependent CP asymmetry
Updated and new results
Gianluca Cavoto

3. g from direct CP violation
Interference when D final state common to both D0 and D0
Relative size (rB) of B decay amplitudes
Not well constrained by theory.
Larger rB, larger interference, better g experimental precision
BaBar hep-ex/
Belle hep-ex/
Relative strong phase (dB) unknown
Different incarnations…
Gianluca Cavoto

4. Gronau London Wyler method
Theoretically
clean, but with 8-fold
ambiguity
Gronau London Wyler method
D decays into CP eigenstate
Select CP-even and CP-odd final states
3 observables, 3 unknowns
Normalize to D0 decay into flavour state (K-p+)
Experimentally
CP modes: small D0 branching ratio
Gianluca Cavoto

5. Analysis techniques High reconstruction efficiency Cerenkov angle data
No charge confusion.
Clear separation Dp/DK
Reject
events
topological variables in
Neural Network or Fisher discriminant
data MC
BF(B  DK) ~ 10 -4, BF(D f) ~ reconstruct as many f final states as possible
Gianluca Cavoto

6. B-D0CPK(*)- yields Combine several final states D0CP K -
CP+ (p+p-,K+K-)
NBB=
CP- (KSp0)
D0p background
D0CP K* - (K* -  KSp -)
Adding KSf, KSw
B- CP+
B- CP-
B+ CP+
B+ CP-
NBB=
Gianluca Cavoto

7. GLW B-D(*)0CPK(*)- results
D0CP K* - (K*-  KSp -)
NBB=
NBB=
D*0 (D0CPp0)K -
Additional systematic error
on ACP- ( CP even background)
NBB= \
Loose bound on rB
From DCPK*
More CP eigenstate final
states still to be added…
More statistics needed to constrain g
Gianluca Cavoto

8. Atwood Dunietz Soni method
D decay into flavor state dB dD
Count B candidates with opposite sign kaons
Input:
Phys.Rev.Lett.91:171801,2003
D decay strong phase dD unknown
Gianluca Cavoto

9. ADS results No signal in current dataset NBB=227 106 D0K D*0(D0p0)K
D*0(D0g)K
NBB=
No signal in current dataset
Gianluca Cavoto

10. rB from ADS method Sensitive to rB (RADS~r2B) RADS R*ADS
D*0(D0p0)K
D*0(D0g)K
D0K
RADS
R*ADS
No AADS measurement
Not easy to determine g
Gianluca Cavoto

11. B- D(*)0 K- D0(KSpp) Dalitz analysis
If we knew the charm phase shift dD?
B- D(*)0 K- D0(KSpp) Dalitz analysis
Amplitude for B-/B+  “D0”K-/K+
Sensitivity to g
Isobar model for f(m2+ ,m2- )
can fix phase variation dD across Dalitz plot.
Only two-fold ambiguity
in g extraction
r(770)
DCS K*(892)
g=75,d=180,rB=0.125
Gianluca Cavoto

12. D0(KSp+p-) Dalitz model
Determined on D* D0p sample
D0(KSp+p-) Dalitz model
CA K*(892)
Plot of mpipi
r(770)
DCS
K*(892)
No D-mixing, No CP violation in D decays
Gianluca Cavoto

13. B-D0K-, B-D*0K- B+ 261 19 B- 83 11 40 8 NBB=211 106
DCS K*(892)
261 19
D0K
83 11
D*0(D0p0)K
40 8
DCS K*(892)
D*0(D0g)K
Dalitz projection for
mES >5.272 GeV/c2
Signal plus background
PDF superimposed
Gianluca Cavoto

14. g from B-D(*)0[KSp+p-]K-
With current statistics, no rB sensitivity for rB<0.10
180
A posteriori rB(rB*) with uniform a priori g
D0K-
-180 rB
0.3
D0K-
D*0K-
180
68% g
D*0K-
95% 0.
0.3 0.
0.3
-180
r*B
0.3
Bayesian
confidence regions
Dalitz model syst
Gianluca Cavoto

15. Critical rB… GLW ADS D0 Dalitz rB g g measurement from
g sensitivity projection for 500 fb-1
rB =0.1
D0 Dalitz
s(g)
rB =0.2
GLW only
ADS only
(dD and dB
unknown)
GLW+ADS
rB =0.3
g = 62o rB g
g measurement from
combination of many modes
(multiple constraints on rB) 90
180
From ADS
Gianluca Cavoto

16. sin(2b+g) with B0 D(*)-p+/r+
Time dependent CP analysis
sin(2b+g) with B0 D(*)-p+/r+
The final state is accessible from both B0 and B0
~l2
~l4
favored bc amplitude
suppressed bu amplitude
 time-dependent CP violation arises from
interference of mixing and decay:
Asymmetry
parameters
Lepton tag
Exclusive reconstruction of D-p+, D*-p+,D-r+
D*r
Combinatoric BB
Peaking BB
Continuum
Partial reconstruction of D*-p+
Gianluca Cavoto

17. B0  D(*)0 K(*)0 Search for b  u transition (self tagging mode)
NBB=
B0  D(*)0 K(*)0
Sensitivity given by
Search for b  u transition
(self tagging mode)
Eventually TD analysis…
No signal…
Gianluca Cavoto

18. Unitarity triangle constraints
Confidence regions in r-h plane
hep-ph/ .
Combination of BaBar a and c results with uniform
prior in r
68% C.L.
95% C.L.
Improve bound using SU(3)
r from
Search for B0 Dsr
B0D+sp -
overlay the best fit for UT
NBB=90 106
Not encouraging for Dr…
Phys.Rev.Lett.90:181803,2003
Gianluca Cavoto

19. Conclusion More modes and techniques added to measure g
GLW, ADS, D0K Dalitz, time-dep. sin(2b+g)
No single golden technique
Constraints on b u amplitude in B DK
Evidence for small rB
Sensitivity to g relies heavily on rB
g from combination of many modes
Add rb again
Combination of BaBar
GLW+ADS+D0K Dalitz
68 %C.L.
95 % C.L.
Gianluca Cavoto

20. Backup slides
Gianluca Cavoto

21. sin(2b+g): results NBB=110 106
Exclusive reconstruction of D-p+, D*-p+,D-r+
- higher signal purity, lower efficiency
Higher pp resonance
Included in syst.error
Partial reconstruction of D*-p+
- high efficiency, more background
NBB=
Gianluca Cavoto