Meeting BaBar Italia, Capri 10/04/03 Alfio Lazzaro1 Branching Fraction and Direct CP Violation in B 0 K 0 and B h B 0 K 0 and B h Branching Fraction and.

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 1

Branching Fraction and Direct CPBranching Fraction and Direct CPViolation in Violation in

BB00KK 00 and and BB

hh

Branching Fraction and Direct CPBranching Fraction and Direct CPViolation in Violation in

BB00KK 00 and and BB

hh

Alfio LazzaroAlfio LazzaroDipartimento di Fisica and INFN, MilanDipartimento di Fisica and INFN, Milan

on behalf of the BaBar Collaborationon behalf of the BaBar Collaboration

American Physical Society 2003, PhiladelphiaAmerican Physical Society 2003, Philadelphia

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 2

Physics Motivation

Analysis Strategy: Samples, Event Selection, ML fits

Results on Branching Fractions and Charge asymmetries

Conclusion

OverviewOverviewOverviewOverview

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 3

• Measurements of Branching Fractions allow constraints on phenomenological models

• Charge asymmetries (Ach) expected large (>20%) in BK (Soni, PRL 43, 242 (1979)) and B (Gronau, PRL 79, 4333 (1997))

Physics MotivationPhysics MotivationPhysics MotivationPhysics Motivation

Need precise measurements

Previous Measured Branching Fractions (106):Previous Measured Branching Fractions (106):

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 4

Data Samples and Sub-channelsData Samples and Sub-channelsData Samples and Sub-channelsData Samples and Sub-channels

We considered 3 channels:We considered 3 channels:

Reconstructed inReconstructed in

We have used 81.9 fbon-resonance (88.9 millions of BB pairs)

We have used 81.9 fbon-resonance (88.9 millions of BB pairs)

_

(23%) (39%)

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 5

Event selectionEvent selectionEvent selectionEvent selection • Beam energy to constraint B mass and energy:

• Event shapes to distinguish B events from continuum udsc:Fisher discriminant combining 4 variables:

•direction of B thrust axis wrt beam direction•direction of B momentum wrt beam direction•2 Legendre moments of the energy flow of rest of event wrt B thrust axis

|cos (thrust)| < 0.9

• Loose cuts based on shapes variables, PID and kinematical quantities of secondary daughters, Cherenkov angle cut for h selection.

We prepare the input toWe prepare the input to Maximum Likelihood Fit Maximum Likelihood Fit

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 6

• Two types of background:

qq (continuum ) dominant

bb (non continuum ) ~ 1% – 2%

•Observables: E, mES , Fisher, mass

ObservablesObservables ObservablesObservables

_

_

We useWe use Unbinned Extended Maximum Unbinned Extended Maximum Likelihood (ML) Fit Likelihood (ML) Fit to extract signal to extract signal

yields and charge asymmetriesyields and charge asymmetries

We useWe use Unbinned Extended Maximum Unbinned Extended Maximum Likelihood (ML) Fit Likelihood (ML) Fit to extract signal to extract signal

yields and charge asymmetriesyields and charge asymmetries

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 7

Results for Results for KK00 and and hhResults for Results for KK00 and and hh

First observationFirst observationPreliminary

Meeting BaBar Italia, Capri 10/04/03

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Negative logLikelihoodNegative logLikelihoodNegative logLikelihoodNegative logLikelihood

Dashed blue line:

Dotted red line:

Solid black line:

Meeting BaBar Italia, Capri 10/04/03

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mmESES and and EE projections projections mmESES and and EE projections projections

Shaded histograms represent

Meeting BaBar Italia, Capri 10/04/03

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Systematics on BF and ASystematics on BF and AchchSystematics on BF and ASystematics on BF and Achch

Sources Error on yields • Systematics due to ML fit efficiency and bias

• Daughter Branching fractions

• Reconstruction efficiencies (, 0, KS, charged tracks)

• Other sources: BB Number, MC statistics,

PID, …

0.3 - 0.5

0.03 - 0.4

0.3 - 2.0

0.03 - 0.6

Total systematic error on BF:

Charge AsymmetriesSystematic on charge dependence bias

7.1% (h +) 7.7% ()

1.1%

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 11

KK00, , KKKK00, , KK

• Branching Fraction for BK larger than initially expected

by theory

• Tree diagrams are Cabibbo suppressed:

• Interference between two penguin diagrams and the known – mixing angle conspire to greatly enhance BK

and suppress BK (Lipkin, Phys. Lett. B 254, 247 (1991))

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 12

Results for Results for KK00 and and KKResults for Results for KK00 and and KK

BFBF

AAchch

Preliminary

See also talk by Fred Blanc, Session T11

See also talk by Fred Blanc, Session T11

Meeting BaBar Italia, Capri 10/04/03

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mmESES and and E ProjectionsE Projections mmESES and and E ProjectionsE Projections

Shaded histograms represent

Meeting BaBar Italia, Capri 10/04/03

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ConclusionConclusionConclusionConclusion

We have presented the following preliminary results:

First observation

First observation

2.52.5

Suppressed BKEnhanced BK

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 15

Altre Analisi in CorsoAltre Analisi in CorsoAltre Analisi in CorsoAltre Analisi in Corso

B–>B–> ''• BAD-462 Supporting Document

BAD-605 Physics Note

Risultati di CLEO

B0

d

b_

W+

t_

d

d_

gs

s_

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 16

B–>B–> ''B–>B–> ''

• Analisi finita da tempo

• Yields negativi

• Quindi abbiamo fatto una analisi

di tipo Bayesiano

• Si sta ancora discutendo con

i referee (Bob Cahn) ed altri

esperti sul modo piu’ appropriato

di presentare i risultati

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 17

B–>B–> ’K’KLLB–>B–> ’K’KLL

• Supporting document : BAD-591

• Scopo : Misura di BR e Time-Dependent CP-Violating

Asymmetries ( analogo a quanto abbiamo fatto con S)

•Attualmente usiamo il sotto-decadimento ma in

un prossimo futuro verra’ aggiunto °

•Statistica usata : RUN 1 + RUN 2

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 18

B–>B–> ’K’KLLB–>B–> ’K’KLL

• Funzioni di likelihood per la identificazione delle KL ntimo

• Constraint su MB e sulle direzioni per la ricostruzione cinematica

• Analisi ML con le variabili:

Mse , M , M , Fisher

• Forte presenza di fondo comporta

tagli su cos T bassa ( 6 % )

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 19

B–>B–> ’K’KLLB–>B–> ’K’KLL

• Ora stiamo cercando di aumentare l’efficienza di ricostruzione sostituendo alcuni tagli e il discriminante di Fisher con una rete neurale (NN). Uscita della rete usata come taglio per input ML

E , M , M• Analisi ML utilizzando le variabili :

• Analisi cut & count nel piano : ( NN , )

• Control Sample : e+e- ( S L )

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 20

B–>B–> ’K’KSSB–>B–> ’K’KSS

• Stiamo misurando il BR di questo canale nel sottodecadimento

e S + -

• Stiamo aggiornando l’analisi a tutta la statistica (Run1 + Run2)

• Useremo questi dati nella prossima analisi CP-time dependent

• Supporting Document : BAD-488

Meeting BaBar Italia, Capri 10/04/03

Alfio Lazzaro 21

B–>B–>

B–>B–>

• Stiamo misurando il BR di B nei sottodecadimenti

con e (

• Per i canali stiamo usando le varie combinazioni dei sottodecadimenti con e 3, e In queste analisi siamo ancora agli inizi!