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B Decays to Measure g

Stephen Bailey Harvard University for the BaBar Collaboration PASCOS 2003 Mumbai, India. B Decays to Measure g. Background. CP violation with B 0 -> y K S (sin2 b ) is well established Agrees with Standard Model Now we need to overconstrain the unitarity triangle to check consistency

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B Decays to Measure g

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  1. Stephen Bailey Harvard University for the BaBar Collaboration PASCOS 2003 Mumbai, India B Decays to Measure g S. Bailey / BaBar : B decays to Measure gamma

  2. Background • CP violation with B0 -> yKS (sin2b) is well established • Agrees with Standard Model • Now we need to overconstrain the unitarity triangle to check consistency • g = arg(VudVub* / Vcd Vcb*) • g = -arg(Vub)in standard phase convention • Results from BaBar at PEP-II: e+e- -> U(4S) -> BBbar • ~88 million BBbar pairs h g r S. Bailey / BaBar : B decays to Measure gamma

  3. Many Methods – none are easy • Amplitude relationships with B- -> D0CP K- and friends • “Squashed” amplitude triangles: BR(B- D0bar K-) << BR(B- D0 K-) • Interference involving doubly Cabibbo suppressed D0 decays • sin(2b+g) with B0 -> D(*)-p+, r+, a1+, … • Cabibbo suppressed B0 -> D(*)+ p- • Use B0 -> Ds(*)p and SU(3) to estimate B0 -> D(*)+ p- • Progress on both full and partial reconstruction techniques • B -> pp, Kp, KK • Several options with various theoretical trade-offs S. Bailey / BaBar : B decays to Measure gamma

  4. B D0CP K and friends • D0CP= (D0± D0bar) / Ö2 : CP even or odd decays, e.g. K+K- • Measure sides of amplitude triangles to determine g • Ö2 A(B- -> D0CPK-) = A(B- -> D0K-)±A(B- -> D0barK-) • Ö2 A(B- -> D0CPK-) = A(B- -> D0K-)± |A(B- -> D0barK-)| e-igeid • Sensitivity to g depends on r = |A(B- -> D0barK-)| / |A(B- -> D0K-)| strong phase weak phase S. Bailey / BaBar : B decays to Measure gamma

  5. B- D0 K- hep-ex/0207087 D0 -> Kp only • Use D0 -> K-p+, K-p+p-p+, K-p+p0 B -> D0p B -> D0K (81M BBbar pairs; 75 fb-1) PDG: BF(B- -> D0p-) = (5.3±0.5)x10-3 D0 -> Kp only with kaon ID cut and 3s mES cut S. Bailey / BaBar : B decays to Measure gamma

  6. B D0[K+K-] K 36.8 ± 8.4 ± 4.0 signal events B D0[p+p-] K Upcoming backgrounds from B -> ppK B D0CP K hep-ex/0207087 S. Bailey / BaBar : B decays to Measure gamma

  7. strong phase weak phase B D0CP K and friends hep-ex/0207087 • Direct CP asymmetry from D0CP states: ACP = 0.17 ± 0.23 +0.09/-0.07 (81M BBbar pairs; 75 fb-1) S. Bailey / BaBar : B decays to Measure gamma

  8. B- D0bar K- • Hard: BR(B- D0bar K-) << BR(B- D0 K-) • Interference from doubly Cabibbo suppressed D0 decays: • B- -> D0barK- (small) --> K+p- (big) • B- -> D0 K- (big) --> K+p- (small) • Plan: • Measure B- -> D0(bar) K-w/ D0bar -> K+p-, K+p-p+p-, K+p-p0 • Measure Multiple D0CP modes • See Gronau, hep-ph/0211282 S. Bailey / BaBar : B decays to Measure gamma

  9. B D0CP K Summary hep-ex/0207087 • B- -> D0 K- measured • R(B -> D0K/D0p) = (8.31 ± 0.35 ± 0.20)% • D0CP -> K+K- : initial results available • Direct Asymmetry: ACP = 0.17 ± 0.23 +0.09/-0.07 • More modes (e.g. D0CP -> pp) in progress • More data coming too… • Cabibbo suppressed modesin progress… (81M BBbar pairs; 75 fb-1) S. Bailey / BaBar : B decays to Measure gamma

  10. Both D(*)+p- and D(*)-p+ from B0 and B0bar Interference -> CP violation B0 B0bar mixing : e-i2b b -> u : Vub ~ e-ig Large difference in branching fractions: BFfavored(B0 -> D(*)-p+) ~ 3x10-3 BFsuppressed(B0 -> D(*)+p-) ~ 10-6 Small CP violating effect expected (2%) Measure one weak phase (2b+g) anda strong phase (d) for each mode in standard phase convention sin(2b + g) with B0 D(*)p S. Bailey / BaBar : B decays to Measure gamma

  11. |A(B0bar -> D(*)-p+)| |A(B0 -> D(*)-p+)| sin(2b + g) : B0 Ds(*)p hep-ex/0207053 too small to measure w/ current data • |l(*)| = ~ 0.02 • Use B0 -> Ds(*)+p- to estimate|A(B0 -> D(*)+p-)| via SU(3) symmetry • Introduces theoretical uncertainty • B0 -> Ds+p- • Use Ds+ -> fp+, KsK+, K*barK+ • 21.4 ± 5.1 signal events • BF(B0 -> Ds+p-) = (3.2 ± 0.9 ± 1.0) x 10-5 • 84M BBbar pairs; 78 fb-1 • BF(B0 -> Ds*+p-) < 4.1 x 10-5 [90% CL] S. Bailey / BaBar : B decays to Measure gamma

  12. sin(2b + g) : Fully reconstructed B0 D(*)p • Fully reconstruct both Dp and D*p • Time evolution for each state f • Four l’s include one weak phase (2b+g) and two strong phases (d(*)) arg(lD+p-) = -(2b+g+d) arg(lD-p+) = -(2b+g-d) arg(lD*+p-) = -(2b+g+d*) arg(lD*-p+) = -(2b+g-d*) S. Bailey / BaBar : B decays to Measure gamma

  13. sin(2b + g) : Fully reconstructed B0 D(*)p • We have thousands of fully reconstructed B0 -> Dp andB0 -> D*p • The sin(2b+g) fitter is being studied • The results aren’t unblinded yet • mES from B0 -> D-p+ with 5.2 fb-1 • very clean signal • now we have almost 20x more data 5.2 fb-1 B0D-p+ S. Bailey / BaBar : B decays to Measure gamma

  14. sin(2b + g) : Partially reconstructed B0 D*p • Another method: Partial D* reconstruction • Reconstruct low momentum p in D* -> Dp, but not rest of D • More signal events,but also more background • N(tagged) > 40 000 eventsin full dataset 20.3 fb-1 : only a fraction of the current data, but shows approximate S/B S. Bailey / BaBar : B decays to Measure gamma

  15. sin(2b + g) : Partially reconstructed B0 D*p • Unreconstructed D daughters could affect tag sidevertex position measurement • Validate partial reco. method with a lifetime measurement • t(B0) = (1.510 ± 0.040 ± 0.041) ps(with 20.7 fb-1) • cf PDG t(B0) = (1.548 + 0.032) ps • hep-ex/0212012 submitted to PRD • Proceeding with sin(2b+g) fit, results not unblinded yet… S. Bailey / BaBar : B decays to Measure gamma

  16. B0pp, Kp, KK • Amplitude relationships with B -> pp, Kp, KKmay also measure or constrain g • Theoretical interpretation is complicated: • Penguins • Rescattering contributions • SU(3) symmetry breaking • etc. • For a recent brief review, see Fleischer, hep-ph/0207324 • For now we’ll quote branching fractions (BF) and Asymmetries (A) and let you plug the numbers into your favorite theory… S. Bailey / BaBar : B decays to Measure gamma

  17. hep-ex/0207055 hex-ex/0207065 hex-ex/0207063 hep-ex/0206053 B0pp, Kp, KK (81 fb-1 except K0p+, K+K0bar: 54 fb-1) S. Bailey / BaBar : B decays to Measure gamma

  18. Many More Modes • Exploring many other modes which could measure g or 2b+g: • B -> D(*)K(*) • B -> D(*)KS • B -> D KSp • B -> D(*) K(*)p • Dalitz analysis of B -> ppp • etc. S. Bailey / BaBar : B decays to Measure gamma

  19. Outlook • The Good News: We’re making progress • B- -> D0CP K- • Several sides of amplitude triangles measured • ACP = 0.17 ± 0.23 +0.09/-0.07 • sin(2b+g) with B0 -> D(*)p • Decay modes reconstructed • Lifetime measurement checks method • sin(2b+g) fit results in progress • B0 -> pp, Kp, KK • Many branching fractions measured • Need theoretical input for interpretation • Final story will likely involve: • B factory measurements of many decay modes • Hadronic accelerator results with Bs decays • Theoretical input S. Bailey / BaBar : B decays to Measure gamma

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