1 / 21

Constraints on g from Charmless Two-Body B Decays: Status and Perspectives

Constraints on g from Charmless Two-Body B Decays: Status and Perspectives. Workshop on the CKM Unitarity Triangle Second Meeting, IPPP Durham April 5-9, 2003. James D. Olsen Princeton University. Overview.

Download Presentation

Constraints on g from Charmless Two-Body B Decays: Status and Perspectives

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Constraints on g from Charmless Two-Body B Decays: Status and Perspectives Workshop on the CKM Unitarity Triangle Second Meeting, IPPP Durham April 5-9, 2003 James D. OlsenPrinceton University

  2. Overview • g is the weak phase difference between b → u tree and b → s penguin amplitudes • Large penguin contributions facilitate sensitivity to g • One physicist’s garbage (penguin pollution) is another’s gold! • Challenges • Strong phase difficult to calculate • Electroweak penguins (EWP) • Rescattering • All two-body modes are useful • Kp – sensitivity to g • pp – A(p+p0) ~ T, cross-check kinematic assumptions (ACP in p+p0) • KK – constraints on rescattering J. Olsen

  3. General Strategies • Use SU(2) symmetry • Relate decay rates for all Kp modes (use R ≡ ratios of BFs) • Assuming negligible annihilation amplitudes, K0p+→ pure P • Use ACP to remove dependence on strong phase • Provides allowed regions in R vs. g • Use a model • QCD FA, PQCD, Charming Penguins, etc… • Pitfalls? • Electroweak penguins (EWP) • Can be included; constrained by asmmetry in p+p0 • Rescattering • Use decay rates for KK modes to constrain rescattering effects J. Olsen

  4. Experimental Considerations • Charmless decays are Cabibbo suppressed (|Vub|2) • BF(B → KK) ~ 10-8 - 10-6, BF(B → pp) ~ 10-6, BF(B →Kp) ~ 10-5 • Background dominated by • At the (4S) can use kinematics and topology to separate spherical B decays from jetty light-quark production • Particle ID is critical (p/K separation) • BaBar – Detector of Internally Reflected CherenkovLight • Belle – Aerogel • Dominant sources of systematic error (now) • BF: PDF shapes, efficiency • ACP: PDF shapes, possible detector charge bias J. Olsen

  5. BaBar Belle CLEO 81 78 15 Data: B → Kp BF(10-6) K0p+ K+p- BaBar BaBar p+p- J. Olsen

  6. BaBar Belle CLEO 81 78 15 Data: B → Kp Belle Belle K+p0 K0p0 J. Olsen

  7. BaBar Belle CLEO 81 78 15 Data: B → pp BaBar BaBar Fit region Belle p+p- p0p0 r+p- Br(B0→p0p0) ~ Br(B0→p+p-)? J. Olsen

  8. BaBar Belle CLEO 81 78 15 K+K0 Data: B → KK No sign of B → KK PID cross-feed BaBar Belle Belle K+K- K0K0 J. Olsen

  9. Summary of Branching Fractions * J. Olsen *weighted average (speaker’s calculation)

  10. The penguins are out there… • If trees dominate in pp we would have: • Data: first ratio is 0.25  0.08, second is 2.1  0.4 • Destructive P/T interference in p+p- • Color-suppressed tree in p+p0 ? • If penguins dominate in Kp we would have: • Data: J. Olsen

  11. Constraints on P/T BaBar • Use data • P from K0p+ • Two-body BFs • Spp and Cpp • CKM indirect constraint on a • BaBar prefers: • 0.1 < |P/T| < 0.4 • -170 < arg(P/T) < -40 • Belle prefers: • 0.5 < |P/T| < 1.1 • -70 < arg(P/T) < -30 Arg(P/T) P/T Belle Arg(P/T) J. Olsen P/T

  12. Is Rescattering Important? • Could modify branching fractions and CP asymmetries in pp and Kp decays, complicating extraction of a and g • KK decays are more sensitive to rescattering • Could have significant enhancement through (for example) DD or pp intermediate states BF(10-6) No sign of rescattering yet Error on g ~ 5o for g ~ 50o – 60o Lach and Zenczykowski, hep-ph/0206127 *Chen and Li, Phys. Rev D63, 014003 (2000) J. Olsen

  13. Direct CP Violation • Observable asymmetries require |T| ~ |P| and non-trivial weak- (f) and strong-phase (d) differences • For Kp: f = g and |T/P| ~ 0.2 • Presence of d → can’t extract g directly from ACP • Remove d dependence by combining ACP and branching ratios • New Physics could be lurking in the loops! J. Olsen

  14. Direct CP Violation: Results Largest deviations: 2s each in K+p-(BaBar), r+p-(BaBar), and K+p0(Belle) J. Olsen

  15. Model-Independent Constraints on g: Fleischer-Mannel Bound • Assuming SU(2): • If R < 1, leads to excluded regions near g = 90o • Current experimental value: R = 0.95  0.08 • For example, would exclude 13o region around 90o • But still consistent with R = 1 • Unfortunately, not useful… J. Olsen

  16. Model-Independent Constraints on g Buras and Fleischer, Eur. Phys. J. C16, 97 (2000) Combine BF and pseudo asymmetry A0 Neutral B: Charged B: Rn Rc g g

  17. A Specific Model: QCD Factorization Beneke et. al., Nucl. Phys. B606, 245 (2001) Data (2001) Data (2003) Inconsistent? J. Olsen

  18. B-Factory Status Current on-peak data sets ~ 110/fb Current data-taking rates: BaBar ~ 400/pb/dy Belle ~ 500/pb/dy Belle BaBar and Belle expect to integrate 500/fb by 2006 J. Olsen

  19. Projections for end of 2005 2003 2005 (WA) Systematic errors will be important in all observed modes J. Olsen

  20. Summary and Outlook • Experiment has come a long way in three years • 6 out of 10 charmless two-body modes have been observed • Errors are now ~ 5 – 15% • Searches for direct CP violation in ~20 decay modes • No evidence for CP violation • Smallest error = 5% (K+p-) • Penguins are here to stay • Penguin dominance in Kp is now an experimental fact • Destructive P/T interference in pp is evident • <BaBar + Belle> indicate (P/T)pp ~ 0.2 – 0.5 • Upper bounds on KK modes are starting to place non-negligible constraints on rescattering effects J. Olsen

  21. Summary and Outlook • For both model-independent and model-dependent bounds on g, the error depends strongly on the true value • Difficult to predict future errors • Data is useful for constraining current models: QCD FA, PQCD, Charming Penguins, etc… • If a consistent value of g emerges it gives more confidence in model-dependent extraction of a in B → pp • Future (2005) measurements of BFs will be limited by systematic errors: • Fundamental detector uncertainties (neutrals ID, PID, tracking) • ratio of B+/B0 • Chance of observing direct CP violation by 2005? • Error on asymmetries: s(K+p-) ~ 2%, s(K0p+) ~ 3% J. Olsen

More Related