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B Decays to Open Charm (an experimental overview) Yury Kolomensky LBNL/UC Berkeley Flavor Physics and CP Violation Philadelphia, May 18, 2002.

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Presentation on theme: "B Decays to Open Charm (an experimental overview) Yury Kolomensky LBNL/UC Berkeley Flavor Physics and CP Violation Philadelphia, May 18, 2002."— Presentation transcript:

1 B Decays to Open Charm (an experimental overview) Yury Kolomensky LBNL/UC Berkeley Flavor Physics and CP Violation Philadelphia, May 18, 2002

2 05/18/2002 Yury Kolomensky, Open Charm Decays Contents of This Talk  Focus on recent results, in particular “rare” modes, accessible with high statistics samples at CLEO, Belle, and BaBar  Due to time constraints, can’t cover the plethora of modes and measurements shown on the front page Topics:  B  D (*) D (*) : Cabibbo-suppressed: BF, Angular analysis, CPV  B  D (*) K : Cabibbo-suppressed: potential for   Color-suppressed open charm decays B 0  D 0(*) X 0  B 0  D S +(*)   : V ub -suppressed

3 05/18/2002 Yury Kolomensky, Open Charm Decays b  ccd decays: B  D (*) D (*) mixing decay CP B0B0 D ( * )- D(*)+D(*)+ ( ) B0B0 D ( * )- D(*)+D(*)+ ( )  -η eff sin2βsin(ΔmΔt)  Complementary to J/  K S (b  ccs)  Potential sensitivity to New Physics  But: Cabibbo-suppression, penguin pollution, angular structure _

4 05/18/2002 Yury Kolomensky, Open Charm Decays First Things First: Observation of B  D (*) D (*) First observation: CLEO, PRD 62, 032005 (2000)  9.7M B decays  8 signal events  6  observation

5 05/18/2002 Yury Kolomensky, Open Charm Decays Summary of BF Measurements Significance BF (  10  ) CLEO (9 fb -1 ) BaBar (20 fb -1 ) Belle (20 fb -1 )    CLEO (10 fb -1 ) BaBar (20 fb -1 ) Belle (30 fb -1, new) Belle (partial reco)    CLEO (9 fb -1 )  BaBar Belle

6 05/18/2002 Yury Kolomensky, Open Charm Decays  D*D final states are not CP eigenstates: B0B0 D*+D*+ B0B0 D _ D*+D*+ D+D+ D* _D* _ D+D+ D* _D* _ CP conjugation strong phase  D *+ D *- is not an eigenstate either: it is a combination of CP-odd and CP-even amplitudes.  Measure CP content through angular (transversity) analysis for decay products Difficulties for CP Analysis

7 05/18/2002 Yury Kolomensky, Open Charm Decays The angular distribution as a function of one angle,  tr : Where R t is a fraction of P-wave (CP-odd) component Transversity Analysis for B 0  D *+ D *- R t = 0.22  0.18  0.03 signal fit background fit BaBar Results:

8 05/18/2002 Yury Kolomensky, Open Charm Decays CP asymmetry in D *+ D *- and D *+ D - D * N tag = 76 Purity = 80% D * D N tag = 85 Purity = 52% BaBar 1999-2001 data sample: 56fb  on  (4S) Fit for S f and C f Separate S f and C f for D *+ D - and D *- D +. D * D * S = -0.05  0.45  0.05 C = 0.12  0.30  0.05 D * D S +- = -0.43  1.41  0.20 C +- = 0.53  0.74  0.13 S -+ = 0.38  0.88  0.05 C -+ = 0.30  0.50  0.08 Expect 10-fold increase in statistics over the next 4 years

9 05/18/2002 Yury Kolomensky, Open Charm Decays B   D (*)0 K  Decays: Motivation  Determine  through amplitude relationships (up to discrete ambiguities) Gronau &Wiler; Dunietz (1991) Potential for measuring CKM angle 

10 05/18/2002 Yury Kolomensky, Open Charm Decays Experimental Challenges Rate suppressed by about factor of 10 compared to favored mode B   D 0    Small BF  Need to reconstruct D 0 into a CP eigenstate (another Cabibbo penalty)  Particle identification crucial B  Dh  D  KK B  Dh  D  K  h=  h=  (BaBar preliminary)

11 05/18/2002 Yury Kolomensky, Open Charm Decays BF Results CLEO (3 fb -1 ) BaBar (55 fb -1, non-CP modes, new) BaBar (55 fb -1, CP modes, new) Belle (10 fb -1 ) (5.5±1.4±0.5)% (8.31±0.35±0.13)% (8.4±2.0±0.8)% (7.9±0.9±0.6)% Belle (10 fb -1 )(6.8±1.5±0.7)% Belle (10 fb -1 )(7.8±1.9±0.9)% Belle (10 fb -1 ) BaBar (20 fb-1, partial reco) (7.4±1.5±0.6)% (6.6±1.3±0.6)% CLEO (9 fb -1 )(6.1±1.6±1.7)*10 -4 CLEO (9 fb -1 )(3.7±1.5±1.0)*10 -4 CLEO (9 fb -1 )(7.7±2.2±2.6)*10 -4 CLEO (9 fb -1 )(3.8±1.3±0.8)*10 -4

12 05/18/2002 Yury Kolomensky, Open Charm Decays Decays into D 0 CP Belle: 29.1fb -1 sample (preliminary, 2002) Measure amplitude asymmetries for 3 samples: D f : flavor eigenstate D 0  K   + (control sample) D 1 (D CP=+1 ): CP eigenstates D 0  K   + and D 0     + D 2 (D CP=-1 ): CP eigenstates D 0  K S  0, K S  K S  ’, K S  K S  BaBar: 55 fb -1 sample (preliminary, 2002) D f : flavor eigenstate D 0  K   + (control sample) D + (D CP=+1 ): CP eigenstate D 0  K   + Strong phase difference Measure

13 05/18/2002 Yury Kolomensky, Open Charm Decays Direct CP Asymmetry in B  DK ModeExptA CP B ±  D f K ± Belle (new) BaBar (new) B ±  D 1 K ± Belle (new) BaBar (new) B ±  D 2 K ± Belle (new) Belle B ±  D 1 K ± EE Belle B ±  D 2 K ± EE Belle B ±  D f K ± EE

14 05/18/2002 Yury Kolomensky, Open Charm Decays Color-Suppressed Open Charm Decays Test of factorization in Class II B  M c L 0 decays Class I (color-allowed) Class II (color-suppressed) “Naïve” Factorization: a 1 and a 2 two phenomenological (but mode-independent) real parameters that can be determined from data (e.g. Neubert & Stech, hep-ph/9705292)

15 05/18/2002 Yury Kolomensky, Open Charm Decays Color-Suppressed Modes: the Data Recent measurements of color- suppressed and color-favored B  DX light modes  CLEO observation of B 0  D (*)0  0 (2001)  Belle observation of B 0  D (*)0  0, B 0  D (*)0  B 0  D (*)0  (2001)  CLEO new measurements of color-allowed B  D   BaBar new measurement of B 0  D (*)  a   B0D0B0D0 B0D00B0D00

16 05/18/2002 Yury Kolomensky, Open Charm Decays Color-Suppressed Modes: Results ModeExperimentSignificance BF (  10 -4 ) Prediction (*) (  10 -4 ) B0D00B0D00 CLEO (9 fb -1 ) Belle (21 fb -1 ) 12.1 7.9 0.7 B 0  D *0  0 CLEO (9 fb -1 ) Belle (21 fb -1 ) 5.9 3.2 1.0 B0D0B0D0 Belle (21 fb -1 )4.70.7 B 0  D *0  Belle (21 fb -1 )4.31.7 B0D0B0D0 Belle (21 fb -1 )3.80.5 B 0  D *0  Belle (21 fb -1 )3.60.6 BD0BD0 CLEO (9 fb -1 )48 B0DB0D CLEO(9 fb -1 )30 B 0  D (*)  a   BaBar (21 fb -1 ), partial reco 116

17 05/18/2002 Yury Kolomensky, Open Charm Decays Interpretations 2 independent isospin amplitudes: and with non –zero phase difference CLEO analysis (2002, preliminary): (CLEO data) (CLEO and Belle data) » Non-zero strong phase differences: violates the basic assumption of naïve factorization. Sizable final-state rescattering effects in Class II processes (similar analysis: Neubert & Petrov, hep-ph/0108103)

18 05/18/2002 Yury Kolomensky, Open Charm Decays  Motivation: measurement of sin(2  +  ) using B 0  D (*)   Requires amplitude decomposition B 0  D (*)+   and B 0  D (*)     Need to measure Cabibbo-allowed BR=0.0030±0.0004 Cabibbo-suppressed BR not known A(B 0  D (*-)  + ) A(B 0  D (*+)  - ) D(*)  = ~0.02 A(B 0  D s (*-)  + ) SU(3) A(B 0  D (*-)  + ) V ub -suppressed Decay B 0  D S +(*)  

19 05/18/2002 Yury Kolomensky, Open Charm Decays Evidence for B   D s (*)      D  cos 2  C BF (B   D    ) BF (B   D s    )  fD2fD2 f Ds 2 Measurement of the parameter D  d c d BB DsDs  b u s Reconstructed D s  modes  D S      , K *0 K +, K S K +, D S *+  D S +           K *0        K S       Background rejection  helicity angle (for D s      , K *0 K + modes)  Fisher discriminant  cos  thrust  D s  vertex probability (  E, m ES ) of the reconstructed B Also: potential for measuring V ub /V cb through ratios Kim et al, PRD 63, 094506 (2001) (shaky theoretical grounds ?) BaBar, 2002, 56 fb -1

20 05/18/2002 Yury Kolomensky, Open Charm Decays Evidence for B   D s    14.9  4.1 events D    D    BF( B   D s    ) = ( 3.1  1.0  1.0 )  10  5 BF( B   D s    )  BF(D s      ) = ( 1.11  0.37  0.24 )  10  6 BF(B   D s *     10 -5 @ 90% CL BF( B   D s    ) = ( 3.1  1.0  1.0 )  10  5 BF( B   D s    )  BF(D s      ) = ( 1.11  0.37  0.24 )  10  6 BF(B   D s *     10 -5 @ 90% CL B   D s    : significance of the signal = 3.5  BaBar Preliminary B 0  D S +*   B   D s *    : significance of the signal = 2.2  Belle (21.3 fb  ): BF( B   D s    ) <  10 -5, BF( B   D s  K  ) < 7  10 -5

21 05/18/2002 Yury Kolomensky, Open Charm Decays B   D s    : Unofficial (*) Interpretation (*) Riccardo Faccini, private communication Assuming SU(3) symmetry:  What is SU(3) uncertainty ? Assuming naïve factorization (a la Kim et al) and using PDG value for BF(B 0  D S D * ): Experimental error 0.023: but is 15% theoretical uncertainty reliable ?  Need theoretical guidance

22 05/18/2002 Yury Kolomensky, Open Charm Decays Outlook Interesting new data coming from (old and new) B factories  Helicity structure and first CP asymmetries in B  D (*) D (*)  First measurements of direct CP asymmetries in B  DK  First observations of color-suppressed decays open charm decays  First evidence for B   D s     More on the way: ten times more data at both BaBar and Belle by 2005


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