1 / 72

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

phyliss
Télécharger la présentation

Rare B decays

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. 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

More Related