1. B  at B-factories Guglielmo De Nardo Universita’ and INFN Napoli
(on behalf of the BaBar collaboration)

2. Motivation Leptonic B decays in SM allow measurement of fB|Vub|
Helicity suppressed, rare decay.
SM prediction: (0.8  1.4)10-4 using exclusive or inclusive |Vub| values and fB=189 MeV
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

3. New Physics probe
Additional tree level contribution from a charged Higgs
It is not helicity suppressed . Then it may be competitive
For example, in a MSSM model with 2 Higgs doublets
From G.Isidori
hep-ph/
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

4. Tag side reconstructionp e+
Breco
Brecoil
e,,,,a1  
1 or 2 
Full reconstruction of a tag B
 hadronic D(*) X
 semileptonic D(*) l 
Search for evidence of 
In the rest of the event (recoil B) 20 4o 60 80
100
Branching Fraction ( % )
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

5. Signal side selection
Signal kinematics and topology exploited with requirements on
Particle identification, missing momentum, intermediate resonance mass ( 0, a1 )
The most discriminating variable is the remaining energy of what is left un-assigned.
For signal events extra energy is expected to be zero
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

6. Belle analysis ( 447 106 B pairs )

7. Hadronic tags 180 hadronic decay channels for tag B
From known beam energies
Constraint on the energy of the B
The energy constrained mass fitted to get the number of tag B.
N=680 K
Eff=0.29%
Purity =55%
defines a signal region for the tag B
-0.08 GeV < DE < 0.06 GeV, Mbc > 5.27 GeV/c2
~10% systematic uncertainty in ntag
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

8. Extra energy simulation
The simulation has been check on a control sample of “double tag” events
Btag  hadronic, Bsig  D(*) l 
B+B-
494  18
B0B0
7.9  2.2
Total
502  18
Data
458
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

9. Fitted signal yield Fit model parameters determined from MC simulation
Background model
2nd order polynomial
Gaussian peaking bg
Signal model
Gaussian with zero mean
exponential
signal events on a sample of 54 events ( 3.5  )
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

10. Detailed break-down and result
Including the efficiencies in table and tag = 0.136%
hep-ex/ to appear in PRL
using HFAG
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

11. mH vs tan  limits
Assuming the SM contributions to the BR from fB and |Vub|.
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

12. BaBar analysis ( 324106 B pairs )

13. Semileptonic tag B Reconstruct one tag B using semileptonic decays
(B momentum from the beam)
tag = (6.77  0.05  0.10) 10-3
Higher yields but less clean than hadronic tags
2% systematic uncertainty on tag B yield
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

14. Extra energy simulation
Simulation of the extra energy validated with a “double tag” control sample
Fully reconstruct two semileptonic events and look at what is left unassigned
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

15. Signal yield Background shape from MC simulation.
sideband
Events/0.1 GeV
Background shape from MC simulation.
Background yield in the signal region projected from the data sideband
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

16. Results Cut and count method to extract the signal
Likelihood composing poissonian probabilities
Result consistent with no signal at 1.3
hep-ex/
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

17. Results
Calculated the upper limit at 90%CL using a modified frequentist method
A. L. Read, J. Phys. G28, 2693 (2002)
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

18. mH vs tan exclusion plot
BaBar+Belle
(excluded at 95%CL)
LEP, Direct Search
(excluded at 95%CL)
S.Sekula
Assuming UT-fit value for BFSM ( B    ) = (0.85  0.13)10-4
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

19. Conclusions Belle finds a signal of B  decays at 3.5  level
with a sample of 447  106 B pairs.
analysis on the recoil of a fully reconstructed B in hadronic decay modes
BaBar signal less strong. Lower central value
With a sample of 324  106 B pairs
Analysis on the recoil of a B  D(*)l  X decays
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov

20. Conclusions
Belle central value is almost excluded by BaBar upper limit, but two results still consistent.
In medio stat virtus. With more data the two results have to regress to the mean.
Will we be able to see signal of NP in B   ?
The task is hard because we’d like be sensitive to a small deviation (downward) of a small signal
BaBar is currently up-dating both the semileptonic tag and the hadronic tag analyses to the full data set
An analysis with semileptonic tag from Belle would also help to compare results / increase the statistics
Guglielmo De Nardo, CKM Workshop, Nagoya, Nov