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B Decays to Open Charm (an experimental overview)

B Decays to Open Charm (an experimental overview). Yury Kolomensky LBNL/UC Berkeley Flavor Physics and CP Violation Philadelphia, May 18, 2002. Contents of This Talk. Focus on recent results, in particular “rare” modes, accessible with high statistics samples at CLEO, Belle, and BaBar

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B Decays to Open Charm (an experimental overview)

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

  2. 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: • BgD(*)D(*) : Cabibbo-suppressed: BF, Angular analysis, CPV • BgD(*)K : Cabibbo-suppressed: potential for g • Color-suppressed open charm decays B0gD0(*)X0 • B0gDS+(*)p- : Vub-suppressed Yury Kolomensky, Open Charm Decays

  3. D(*)- D(*)- ( ) B0 B0 D(*)+ D(*)+ _ CP • Complementary to J/Y KS (bgccs) • Potential sensitivity to New Physics • But: Cabibbo-suppression, penguin • pollution, angular structure mixing decay bccd decays: BgD(*)D(*) ( ) -ηeff sin2βsin(ΔmΔt) Yury Kolomensky, Open Charm Decays

  4. First Things First: Observation of BgD(*)D(*) • First observation: CLEO, PRD 62, 032005 (2000) • 9.7M B decays • 8 signal events • 6s observation Yury Kolomensky, Open Charm Decays

  5. Summary of BF Measurements BaBar Belle Yury Kolomensky, Open Charm Decays

  6. Difficulties for CP Analysis • D*D final states are not CP eigenstates: D+ D*+ B0 D _ D*_ strong phase CP conjugation D*_ D _ B0 D+ D*+ • 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 Yury Kolomensky, Open Charm Decays

  7. Transversity Analysis for B0gD*+D*- The angular distribution as a function of one angle,qtr: Where Rt is a fraction of P-wave (CP-odd) component BaBar Results: Rt = 0.22  0.18  0.03 signal fit background fit Yury Kolomensky, Open Charm Decays

  8. CP asymmetry in D*+D*- and D*+D- • BaBar 1999-2001 data sample: 56fb-1 on U(4S) • Fit forSfandCf • SeparateSfandCfforD*+D-andD*-D+. D*D* Ntag = 76 Purity = 80% D*D Ntag = 85 Purity = 52% 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 Yury Kolomensky, Open Charm Decays

  9. B-gD(*)0K(*)- Decays: Motivation Potential for measuring CKM angle g: • Determine g through amplitude relationships (up to discrete ambiguities) Gronau &Wiler; Dunietz (1991) Yury Kolomensky, Open Charm Decays

  10. Experimental Challenges • Rate suppressed by about factor of 10 compared to favored mode B-gD0p- • Small BF • Need to reconstruct D0 into a CP eigenstate (another Cabibbo penalty) • Particle identification crucial (BaBar preliminary) BgDh, DgKK BgDh, DgKp h=p h=K Yury Kolomensky, Open Charm Decays

  11. BF Results Yury Kolomensky, Open Charm Decays

  12. Decays into D0CP • Belle: 29.1fb-1 sample (preliminary, 2002) • Measure amplitude asymmetries for 3 samples: • Df : flavor eigenstate D0gK-p+ (control sample) • D1(DCP=+1): CP eigenstates D0gK-K+ andD0gp-p+ • D2(DCP=-1): CP eigenstates D0gKSp0,KSh, KSh’, • KSf, KSw • BaBar: 55 fb-1 sample (preliminary, 2002) • Df : flavor eigenstate D0gK-p+ (control sample) • D+(DCP=+1): CP eigenstate D0gK-K+ Strong phase difference Measure Yury Kolomensky, Open Charm Decays

  13. Direct CP Asymmetry in BgDK Belle Belle Belle B±gD1 K± B±gD2 K± B±gDf K± Yury Kolomensky, Open Charm Decays DE DE DE

  14. Color-Suppressed Open Charm Decays Test of factorization in Class II BgMcL0 decays “Naïve” Factorization: Class I (color-allowed) a1 and a2 two phenomenological (but mode-independent) real parameters that can be determined from data (e.g. Neubert & Stech, hep-ph/9705292) Class II (color-suppressed) Yury Kolomensky, Open Charm Decays

  15. Color-Suppressed Modes: the Data B0gD0p0 • Recent measurements of color-suppressed and color-favored BgDXlight modes • CLEO observation of B0gD(*)0p0 (2001) • Belle observation of B0gD(*)0p0, B0gD(*)0w, B0gD(*)0h (2001) • CLEO new measurements of color-allowed BgDp • BaBar new measurement of B0gD(*)-a1+ B0gD0w Yury Kolomensky, Open Charm Decays

  16. Color-Suppressed Modes: Results Yury Kolomensky, Open Charm Decays

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

  18. A(B0D(*-) +) D(*) = A(B0 D(*+) -) ~0.02 SU(3) A(B0D(*-)+) A(B0Ds(*-)+) Vub-suppressed Decay B0gDS+(*)p- • Motivation: measurement of sin(2+) usingB0 D(*) • Requires amplitude decomposition B0 D(*)+-andB0 D(*)-+ • Need to measure Cabibbo-suppressed BR not known Cabibbo-allowed BR=0.0030±0.0004 Yury Kolomensky, Open Charm Decays

  19. Measurement of the parameterlDp s BF (B0 D- p+) fDs2 BF (B0 Ds+ p-)  l2Dp u cos2qC fD2 b • Reconstructed Ds+ modes • DS+  fp+ , K*0K+ , KSK+, DS*+gDS+g • f K+K-, K*0 K-p+ , KS p+p- • Background rejection • helicity angle (for Ds+  fp+ , K*0 K+ modes) • Fisher discriminant • cosqthrust • Dsp vertex probability • (DE , mES) of the reconstructed B Evidence for B0 Ds(*)+ p- BaBar, 2002, 56 fb-1 Ds+ c p- B0 d d Also: potential for measuring Vub/Vcb through ratios Kim et al, PRD 63, 094506 (2001) (shaky theoretical grounds ?) Yury Kolomensky, Open Charm Decays

  20. 14.9  4.1 events D- r+ D- p+ Evidence for B0 Ds+ p- B0DS+*- B0 Ds+p-: significance of the signal = 3.5 s B0 Ds*+p-: significance of the signal = 2.2 s BaBar Preliminary BF( B0 Ds+p-) = ( 3.1  1.0  1.0 )  10-5 BF( B0 Ds+p-)  BF(Ds+ fp+ ) = ( 1.11  0.37  0.24 )  10-6 BF(B0 Ds*+p- ) < 4.3  10-5 @ 90% CL Belle (21.3 fb-1):BF( B0 Ds+p-) < 11  10-5, BF( B0 Ds+K-) < 7 10-5 Yury Kolomensky, Open Charm Decays

  21. B0 Ds+ p- : 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(B0gDSD*): • Experimental error 0.023: but is 15%theoretical uncertainty reliable ? • Need theoretical guidance Yury Kolomensky, Open Charm Decays

  22. Outlook • Interesting new data coming from (old and new) B factories • Helicity structure and first CP asymmetries in BgD(*)D(*) • First measurements of direct CP asymmetries in BgDK • First observations of color-suppressed decays open charm decays • First evidence for B0 Ds+ p- • More on the way: ten times more data at both BaBar and Belle by 2005 Yury Kolomensky, Open Charm Decays

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