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

2. CKM Workshop 2003 J. Olsen 2 Overview  is the weak phase difference between b → u tree and b → s penguin amplitudes Large penguin contributions facilitate sensitivity to   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  K  – sensitivity to    – A(    0 ) ~ T, cross-check kinematic assumptions (A CP in    0 )  KK – constraints on rescattering

3. CKM Workshop 2003 J. Olsen 3 General Strategies Use SU(2) symmetry  Relate decay rates for all K  modes (use R ≡ ratios of BFs)  Assuming negligible annihilation amplitudes, K 0    → pure P  Use A CP to remove dependence on strong phase  Provides allowed regions in R vs.  Use a model  QCD FA, PQCD, Charming Penguins, etc… Pitfalls?  Electroweak penguins (EWP) Can be included; constrained by asmmetry in      Rescattering Use decay rates for KK modes to constrain rescattering effects

4. CKM Workshop 2003 J. Olsen 4 Experimental Considerations Charmless decays are Cabibbo suppressed (  |V ub | 2 )  BF(B → KK) ~ 10 -8 - 10 -6, BF(B →  ) ~ 10 -6, BF(B →  K  ) ~ 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 (  /K separation)  BaBar – Detector of Internally Reflected Cherenkov Light  Belle – Aerogel Dominant sources of systematic error (now)  BF: PDF shapes, efficiency  A CP : PDF shapes, possible detector charge bias

5. CKM Workshop 2003 J. Olsen 5 Data: B → K  K+-K+- K0+K0+ BaBar BaBar Belle CLEO 81 78 15 BF(10 -6 ) 

6. CKM Workshop 2003 J. Olsen 6 Data: B → K  K+0K+0 K00K00 Belle BaBar Belle CLEO 81 78 15

7. CKM Workshop 2003 J. Olsen 7 Data: B →  Fit region  Belle +-+- 0000 BaBar BaBar Belle CLEO 81 78 15 Br(B 0 →      Br(B 0 →     )?

8. CKM Workshop 2003 J. Olsen 8 Data: B → KK K+K-K+K- K+K0K+K0 K0K0K0K0 Belle BaBar PID cross-feed BaBar Belle CLEO 81 78 15 No sign of B → KK

9. CKM Workshop 2003 J. Olsen 9 Summary of Branching Fractions * weighted average (speaker’s calculation) *

10. CKM Workshop 2003 J. Olsen 10 The penguins are out there… If trees dominate in  we would have:  Data: first ratio is 0.25  0.08, second is 2.1  0.4 Destructive P/T interference in     Color-suppressed tree in    0 ? If penguins dominate in K  we would have:  Data:

11. CKM Workshop 2003 J. Olsen 11 Constraints on P/T Use data  P from K 0  +  Two-body BFs  S  and C   CKM indirect constraint on  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 P/T Arg(P/T) Belle BaBar P/T

12. CKM Workshop 2003 J. Olsen 12 Is Rescattering Important? Could modify branching fractions and CP asymmetries in  and K  decays, complicating extraction of  and  KK decays are more sensitive to rescattering  Could have significant enhancement through (for example) DD or  intermediate states BaBarPQCD * K+K-K+K- <0.60.05 K+K0K+K0 <2.21.7 K0K0K0K0 <1.61.8 BF(10 -6 ) No sign of rescattering yet * Chen and Li, Phys. Rev D63, 014003 (2000) Error on  ~ 5 o for  ~ 50 o – 60 o Lach and Zenczykowski, hep-ph/0206127

13. CKM Workshop 2003 J. Olsen 13 Direct CP Violation Observable asymmetries require |T| ~ |P| and non-trivial weak- (  ) and strong-phase (  ) differences  For K  :  =  and |T/P| ~ 0.2 Presence of  → can’t extract  directly from A CP  Remove  dependence by combining A CP and branching ratios New Physics could be lurking in the loops!

14. CKM Workshop 2003 J. Olsen 14 Direct CP Violation: Results Largest deviations: 2  each in K +   (BaBar),      BaBar), and K +   (Belle)

15. CKM Workshop 2003 J. Olsen 15 Model-Independent Constraints on  : Fleischer-Mannel Bound Assuming SU(2):  If R < 1, leads to excluded regions near   Current experimental value: R = 0.95  0.08  For example, would exclude  13 o region around 90 o  But still consistent with R = 1 Unfortunately, not useful…

16. Model-Independent Constraints on  Neutral B:Charged B:  RnRn RcRc  Buras and Fleischer, Eur. Phys. J. C16, 97 (2000) Combine BF and pseudo asymmetry A 0

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

18. CKM Workshop 2003 J. Olsen 18 B-Factory Status Belle BaBar and Belle expect to integrate 500/fb by 2006 Current on-peak data sets ~ 110/fb Current data-taking rates: BaBar ~ 400/pb/dy Belle ~ 500/pb/dy

19. CKM Workshop 2003 J. Olsen 19 Projections for end of 2005 20032005 (WA)  B/B(stat) 1.6 2.4 2.7 4.5 3.7 6.1 Systematic errors will be important in all observed modes

20. CKM Workshop 2003 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 +  - ) Penguins are here to stay  Penguin dominance in K  is now an experimental fact  Destructive P/T interference in  is evident  indicate (P/T)  ~ 0.2 – 0.5 Upper bounds on KK modes are starting to place non- negligible constraints on rescattering effects

21. CKM Workshop 2003 J. Olsen 21 Summary and Outlook For both model-independent and model-dependent bounds on , 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  emerges it gives more confidence in model-dependent extraction of  in B →  Future (2005) measurements of BFs will be limited by systematic errors:  Fundamental detector uncertainties (neutrals ID, PID, tracking)  ratio of B + /B 0 Chance of observing direct CP violation by 2005?  Error on asymmetries:  (K +    (K 0   