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Rare B decays

Rare B decays. Youngjoon Kwon Yonsei University. Introduction Hadronic two-body states - non-factorizable processes Radiative & EW penguins Special subject: B  D sJ X. Overview. Physics Goals in B-factories. Establish CP violation in B decays

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Rare B decays

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  1. Rare B decays Youngjoon Kwon Yonsei University • Introduction • Hadronic two-body states - non-factorizable processes • Radiative & EW penguins • Special subject: B  DsJ X Overview Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  2. Physics Goals in B-factories • Establish CP violation in B decays and over-constrain the SM picture of CP violation • any inconsistency? • Measure fundamental parameters of SM • 10 (out of 18, not counting neutrino masses, yet) parameters are related with quark flavors • Belle, in particular, measures CKM triangle parameters; angles&sides • Search for rare/forbidden decays and explore new physics effects Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  3. The major players in B physics Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  4. Clean environment of B-factories Energy difference: Beam-constrained mass: Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  5. B-factory with a clean initial state • Kinematically clean environment of B production and decays • Provides an excellent laboratory to search for new particles & measure their properties • For example, B  K X(3872), K hc(2S) Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  6. W+ V*ub W+ g “Rare B decays” • b  c W* is the dominant B decay process • others are suppressed due to • CKM suppression: b  u • Loop effect (“penguin”): b  s, b  d Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  7. Motivation for Rare B decays • SM is a very good approximation to reality. i.e., for most processes • Need to consider processes where is small in order to be sensitive to new physics. • e.g. processes dominated by penguin loops • Compare Nature (exp.) with SM prediction for those sensitive processes • Find New Physics or learn new lessons Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  8. Where to look for – two starting points • CPV in f Ks • Do we understand penguins? • Radiative, EW • BF, ACP • p0 p0 as an ingredient for f2 (a) • Do we understand the strong-interaction part? • QCDF, pQCD • Color-suppressed modes Let’s start with charmless 2-meson modes and see what we can learn! Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  9. Charmless 2-meson final states • Observables • BF • ACP • polarization, etc. • Experimental concerns • continuum background • hadron ID: Cherenkov + dE/dx + TOF • on interpretation • isospin, SU(3) • Final state re-scattering Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  10. B produced (almost) at rest in Y(4S) frame Isotropic B Jetty Continuum Combine into a Fisher (or NN) Monte Carlo u,d,s,c background Signal Arbitrary Units Fisher Discriminant Discrimination of and Continuum Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  11. W s t W g Vub • cleanest modes • Both tree & penguin processes  can lead to direct CPV • may provide some info. on f2(a) & f3(g) but complicated, due to hadronic effects Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  12. ) Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  13. Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  14. W+ V*ub W+ g T/P ratio? p+p0 K0p+ Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  15. ACP in - Belle result (152 million BB) Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  16. Comparison w/ theory: BF & Acp Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  17. B0 +  - NS = 93 ±22±9 BaBar [> 5] Cos(1) MES   Longitudinal pol. in B → V V fL = L /  100% Pol  CP even Expect: fL ~ 1 – O(M2V/M2B) Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  18. B r+ r0 (Belle) Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  19. B → r r and r K*[BaBar &Belle] • CP asymmetries are consistent with zero • Longituidnal polarization is ~1 as expected  CP even Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  20. Grossman Quinn bound PRD 58 (1998) 017504 | - Eff| < 50o () and < 20o () at 90% CL + - is dominantly longitudinal polarised, CP-even final state Grossman-Quinn bound : BF give model-independent limits to the CP angle  Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  21. A concern on G-Q bound from modifications from final-state interactions non-resonant background Let’s consider a few decay modes potentially sensitive to FSI ! Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  22. Not directly accessible through the spectator process • Sensitive to W-exchange, or final state rescattering  potential for generating large theory uncertainty in extracting CKM angle f3from hadronic B decays • Wide range of predictions: (0.3 ~ 6)x10-5 Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  23. BF is consistent with p-QCD calculation, but in the upper edge of prediction Similar FSI amplitudes – enhanced by (uu)/(ss) – should exist for color-suppressed modes such as D0 p0, etc. 6.4ssignificance! Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  24. Color-suppressed B decays consistently larger than the factorization model FSI re-scattering / W-exchange? Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  25. Color-suppressed B decays Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  26. Where to look for – two starting points • CPV in f Ks • Do we understand penguins? • Radiative & EW • BF, ACP • p0 p0 as an ingredient for f2 (a) • Do we understand the strong-interaction part? • QCDF, pQCD • Color-suppressed modes Now, let’s move on to look at the situation in the penguin sector! Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  27. q s B+,0 q s K(*) u u B   K(*) • Dominated by a single process (penguin)  Expect similar BF for all modes • Note: BF(B+) < 4x10-7 [90% CL] If large, it might indicate a large FSI • Longitudinal polarisation (expected) ~1 Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  28. Belle Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  29. B   K*angular distributions Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  30. B   K*angular distributions Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  31. B   K(*) summary BaBarBelle New physics, in penguin? (Y. Grossman hep-ph/0310229) Or, something new to learn in phenomenology? Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  32. BF(B±fK±) at CDF powerful vertex trigger makes CDF a contender • BR(B±fK±) /BR(B±J/y K±) = 0.0068 ±0.0021 (stat.) ± 0.0007 (syst.) Using PDG 2002 for BR(B±J/y K±): • BR(B±fK±) = (6.9 ± 2.1 (stat.) ± 0.8 (syst.)) x 10-6 Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  33. Electroweak Penguins First penguin observation CLEO, PRL 1993

  34. Branching Fractions (x 10-6) Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  35. Eg spectrum in B  Xs g Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  36. Eg in B  Xs g (CLEO, 2001) Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  37. Eg in B  Xs g (Belle) Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  38. Eg in B  Xs g (Belle) Signal selection is optimized for max. significance in 1.8 ~ 1.9 GeV Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  39. CLEO Belle

  40. CP asymmetry in B  Xsg • CP asymmetry is expexted to be small (<1%) in SM • some non-SM models allow large (~10%) ACP without changing the BF • possible contamination from Xdg (ACP can be large)  but negligible in our measurement Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  41. CP asymmetry in B  Xsg Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  42. ACP(B  Xsg) Belle tagged as ambiguous Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  43. ACP(B  Xsg)BaBar Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  44. ACP(B  Xs g)Summary Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  45. Exclusive: B  K*g Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  46. B  K* g asymmetries Isospin asymmetrySM << (5~10)% CP asymmetry SM << 0.01 Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  47. Exclusive B  Xdg Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  48. Exclusive B  Xdg Standard Model predictions for BF’s Prior measurements (in 10-6) Ali & Parkhomenko (2001) Bosch & Buchalla (2001) CLEO Belle BaBar Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  49. Excl. B  Xdg unbinned 2D max. likelihood fit to DE and Mbc Fit region: |DE| < 0.3 GeV 5.2 < Mbc < 5.3 GeV Physics in Collision, June 27-29, 2004, Youngjoon Kwon

  50. B  Xdg fitting Physics in Collision, June 27-29, 2004, Youngjoon Kwon

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