1. Charmless Quasi-two-Body Modes at BaBar
Fernando Palombo
Dipartimento di Fisica and INFN, Milan
for The BaBar Collaboration
ICHEP’04 August 16 – 22 , 2004 Beijing, China
18/08/04
Fernando Palombo , ICHEP 2004

2. Fernando Palombo , ICHEP 2004
Outline
Motivation
Analysis Technique : Overview
B0 →  
B+ →  +, B+ →  +
B0 → 
B0 → a1(1260) -
B0 →ρ0 KS
B0 → KS KS KS
Conclusion +
18/08/04
Fernando Palombo , ICHEP 2004

3. Fernando Palombo , ICHEP 2004
Motivation
We look to processes dominated by penguin loops or CKM-suppressed decay
(Rare Decays)
An optimal place for measurements sensitive to new physics ( new contributions to the penguin amplitude beyond the SM)
Check of QCD Factorization, Perturbative QCD, Flavour SU(3)
18/08/04
Fernando Palombo , ICHEP 2004

4. Analysis Technique : Overview
Unbinned Maximum Likelihood (ML) Fit
Kinematic and event shape variables
Apply loose cuts to keep side-bands for background fitting
Main background : e+e- → q q continuum (q = u,d,s,c)
fit accounts also for B B background
Extract from ML fits:
yields, charge asymmetries, efficiencies, PDF parameters
Several Crosschecks
“Toy MC” experiments, control samples
Analyses presented in this talk done in Q2B approximation
18/08/04
Fernando Palombo , ICHEP 2004

5. Fernando Palombo , ICHEP 2004
Expected dominated by b → s loop amplitudes
K+ K, *+,  sK* enhanced
+ K K*+ * suppressed
(Lipkin,199)
Interference
Ali et al., PRD59, (1999), M. Z. Yang et al., NPB609,469 (2001)
M. Beneke et al., NP B651,225(2003), H.K. Fu et al., PRD69, (2004)
Chiang et al., PRD69, (2004)
ICHEP/ BaBar-Conf-04/023
18/08/04
Fernando Palombo , ICHEP 2004

6. New Measurement of B0 →
New measurement with
BB pairs .
ηK0
Now observed by BaBar
PRL 92, (2004)
Predicted large charge asymmetry
Chiang et al., PRD69,034001(2004)
18/08/04
Fernando Palombo , ICHEP 2004

7. Fernando Palombo , ICHEP 2004
B+→ + and B+→ +
Expected dominated by a CKM-suppressed tree diagram
Vub
ICHEP / BaBar-Conf-04/023
18/08/04
Fernando Palombo , ICHEP 2004

8. New Measurements of B+→ + and B+→ +_ _
BB pairs used in this analysis
+
+
18/08/04
Fernando Palombo , ICHEP 2004

9. New Measurement of B0 →
Subm.
to PRL _
Measurements done with BB pairs _
Remeasurement done with BB pairs
As expected we improve upper limits.
Very interesting for calculation of upper bound on ΔS in
B0 decay modes dominated by penguins
18/08/04
Fernando Palombo , ICHEP 2004

10. Fernando Palombo , ICHEP 2004
Isoscalars ULs and ΔS
With new ULs in B decays to isoscalar pairs measured by BaBar
great improvement in the bounds of ΔS = S – sin 2 β
S is the coefficient of sin term in time evolution of the system
sin 2 β is S measured in B0 decays to charmonium K0
Previous bound
New bounds
Gronau, Rosner,Zupan hep-ph/
2003 BaBar + Belle average η'K0
BaBar new measurement in η'K0 :
S=0.27 ±0.14 ±0.03 ( see Hoecker
C=-0.21± 0.10 ±0.03 talk, this conf )
see also :Grossman et al.
PRD68 , (2003)
18/08/04
Fernando Palombo , ICHEP 2004

11. Fernando Palombo , ICHEP 2004
B0→ a1+- (a1→++-)
Rare decay with a BF not yet measured.
These decays can be used to study CP asymmetry
for an independent measurement of sin 2α
But first we have to measure the BF to see if there
is any signal.
Analysis done with a statistics of BB pairs.
Simple analysis done in Quasi-2-Body approximation.
Dalitz plot analysis is in progress _
ICHEP/ BaBar-Conf-04/002
18/08/04
Fernando Palombo , ICHEP 2004

12. Measurement B0→ a1- ( a1→++- )
Yield 472 ±46
Br(B0→a1+ -) = (42.6 ± 4.2stat ± 4.1syst ) 10-6
3 
m = 1.19 ± 0.02 GeV/c Γ = 312 ± 55 MeV/c2 a1 a1
Observation of this decay stat. sign. > 10 σ
18/08/04
Fernando Palombo , ICHEP 2004

13. Fernando Palombo , ICHEP 2004
B0→ρ0K0S
Penguin dominated mode :
Another candidate for measuring CP-violating asymmetries (sin 2 β ) in penguin-dominated modes
Analysis done using BB pairs
Several classes of Charmless and Charm backgrounds described by PDFs in ML fit
ICHEP/11/ BaBar-Conf-04/046
18/08/04
Fernando Palombo , ICHEP 2004

14. Fernando Palombo , ICHEP 2004
B0→ρ0K0S
Yield : 99 ± 19
Br(B0→ρ0KS ) = (5.1 ± 1.0 ± 1.2) 10-6
Evidence of this mode at 3.5 σ
(ρ0KS + σ KS ) signal at 6.1 σ
18/08/04
Fernando Palombo , ICHEP 2004

15. Fernando Palombo , ICHEP 2004
B →KS KS KS
Penguin dominated mode :
This decay is not Cabibbo-suppressed
Already measured by Belle with 78 fb-1
Br(B0→KS KS KS ) = ( ± 0.8) 10-6
This measurement done with BB pairs
+1.6
-1.3 _
18/08/04
Fernando Palombo , ICHEP 2004

16. Fernando Palombo , ICHEP 2004
B0→K0S K0S K0S
Yield 71 ± ε = 5.2 % syst. err = 13 %
Br(B0→ KS KS KS ) = (6.5 ± 0.8 ± 0.8) 10-6
Significance > 10 σ
ICHEP/ BaBa-Conf-04/032
18/08/04
Fernando Palombo , ICHEP 2004

17. Fernando Palombo , ICHEP 2004
Conclusion
Observations of B0 → ηK0 , ηρ+, η'+ , a1+ -
Evidence for B0 → ρ at 3.5 σ
B0 → seen with stat. sign. > 10 σ
No evidence in these decay modes for direct
CPV
Severe tests of factorizion models (predictions
of BF, charge asymmetry, etc) KS KS
all new results are preliminary
18/08/04
Fernando Palombo , ICHEP 2004