1. Constraints on α from B Decays at BaBar
32nd International Conference on High Energy Physics
Beijing, China
Constraints on α from B Decays at BaBar
Carlo Dallapiccola
University of Massachusetts, Amherst
For the BaBar Collaboration
17 August, 2004
C. Dallapiccola, ICHEP 2004

2. Outline Introduction and Motivation History of Measurements
Time dependent CP Asymmetry in
Update of
Constraint on Unitarity Triangle angle a
NEW!
17 August, 2004
C. Dallapiccola, ICHEP 2004

3. Motivation: Measuring a
ACP(t) in decay to CP eigenstate:
Measure
Tree If
dominates
17 August, 2004
C. Dallapiccola, ICHEP 2004

4. Motivation: Measuring a
Penguin
But...contribution from
Interferes with Tree:
ACP(t)  sin(2aeff)
aeff = a+dapeng
direct ACP ≠ 0
But can measure dapeng using isospin relations…
17 August, 2004
C. Dallapiccola, ICHEP 2004

5. Motivation: Isospin and rr
Gronau&London,
PRL 65, 3381 (1990)
3 such relations (one for each polarization)
Relative to experimentally simpler B  pp:
Much smaller in rr system
dapeng much smaller!!
17 August, 2004
C. Dallapiccola, ICHEP 2004

6. History: r+r- Observation
But r is a vector r+r- not a CP eigenstate?
Transverse (h=±1) and longitudinal (h=0) helicity states
Non-CP eigenstates
CP eigenstate
* Observation of PRD 69, (2004) *
Run1-2 data (89M )
Measure BF:  5 times larger than p+p-
Measure Polarization
It is almost a pure CP eigenstate (CP =+1)
17 August, 2004
C. Dallapiccola, ICHEP 2004

7. History: r+r0 and r0r0 and measurements: Update of in this talk Mode
BF (10-6) fL
* B+r+r0
* B0r0r0
 B0r+r-
* PRL 91, (2003)
 hep-ex/ , submitted to PRL
89M
17 August, 2004
C. Dallapiccola, ICHEP 2004

8. ACP(t) in B0r+r- Decays
Reconstruct candidates  combine 
Find vertex positions of and other B meson 
Tag flavor of
Compute Dt=tCP-ttag
Fit params
Set to 0 since fL1
17 August, 2004
C. Dallapiccola, ICHEP 2004

9. ACP(t) in B0r+r- Decays
Run1-3 data (122M )
Max. Likelihood fit in 8 dimensional space
mES DE NN MV1, cos(qH)1, Dt
B kinematics
Event shape
r masses
r helicities
Fit for signal yield, polarization, Slong and Clong
Model: true signal, misreco. signal, continuum and
backgrounds
32133 events in fit sample:
87% of background is continuum, 13% B backgrounds
17 August, 2004
C. Dallapiccola, ICHEP 2004

10. ACP(t) in B0r+r- Decays
Run1-3 data (122M )  Preliminary
314±34 Signal Events (205 tagged) fL=1.00±0.02
Events with cleanest tags
mES DE
Fit: total
Fit: bkgd
After cuts on likelihood ratio
BaBar prelim
BaBar prelim
17 August, 2004
C. Dallapiccola, ICHEP 2004

11. ACP(t) in B0r+r- Decays
Run1-3 data (122M )
ACP
BaBar prelim
BaBar Run1-2 (89M )
Hep-ex/ , to PRL
Dt (ps)
17 August, 2004
C. Dallapiccola, ICHEP 2004

12. ACP(t) in B0r+r- Decays: Run4
Run1-4 data (226.6M )  Analysis in progress!
Add 86% more statistics
Comprehensive study of systematics due to interference of signal mode with other decays to p+p-p0p0 final states
Prelim studies show it’s not large
17 August, 2004
C. Dallapiccola, ICHEP 2004

13. Search for B0r0r0 Analysis description similar to that of B0r+r-
First result from Run1-2 (89M )
Updated with Run1-4 data (226.6M )
signal observed
PRL 91, (2003)
NEW!
mES DE
Dominant Syst
a1p interfer: ±7.5 events
PDF variations: ±6 events
B bkgd: ±5.8 events
BaBar prelim
BaBar prelim
17 August, 2004
C. Dallapiccola, ICHEP 2004

14. Constraint on a a Preliminary update on a constraint:
BaBar BF(r+r-), BF(r0r0) and Slong and Clong
World average BF(r+r0)= (HFAG)
prelim
From r0r0 measurement
Run1-2 result: a
17 August, 2004
C. Dallapiccola, ICHEP 2004

15. Constraints on a Using BaBar rr, rp, and pp Measurements
a from rr, rp, pp only
from full CKM fit
(eK, Vub, Dmd,s, sin(2b))
Mirror solutions being disfavored!
From full CKM fit:
17 August, 2004
C. Dallapiccola, ICHEP 2004

16. Conclusion First measurement of ACP(t) in B0r+r- decays Limit on
Updated (2004) with Run1-3 data (122M )
Limit on
Updated with full Run1-4 sample (226.6M )
Low BF allows for relatively clean measurement of a via isospin relations!
Important milestone for B-Factories!
Coming soon  update of ACP(t) in B0r+r- with full Run1-4 data sample and improved analysis
17 August, 2004
C. Dallapiccola, ICHEP 2004

17. Backup Slide
A00 small  Grossman-Quinn bound PRD 58, (1998). Gives same bound on dapeng
Use
17 August, 2004
C. Dallapiccola, ICHEP 2004

18. Backup Slide Distribution of r± helicity distributions for data
Clear demonstration of strong longitudinal polarization
17 August, 2004
C. Dallapiccola, ICHEP 2004

19. Backup Slide Constraints in the r-h plane: 17 August, 2004
C. Dallapiccola, ICHEP 2004