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

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