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Study of CP Violation in B 0   +  –  0 / K S Decays

Study of CP Violation in B 0   +  –  0 / K S Decays. Jinwei Wu Harvard University. Aug 21 st , 2006 . CP violation Extraction of α from B  ρ  decay Extraction of β from B  K S  decay Conclusion. Direct CP Asymmetry. . . . . no CPV.

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Study of CP Violation in B 0   +  –  0 / K S Decays

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  1. Study of CP Violation in B0+–0/KS Decays Jinwei Wu Harvard University Aug 21st, 2006 • CP violation • Extraction of α from B  ρ decay • Extraction of β from B  KS decay • Conclusion

  2. Direct CP Asymmetry     no CPV • Sources of direct CP asymmetries: Interference between two decay amplitudes (Ai) with different strong (i) and weak phases (i) CPV

  3. Time-dependent CP Asymmetry B0 fCP no oscillation oscillation B0 B0 fCP no oscillation B0 oscillation

  4. Mixing induced CPV in Charmless B Decay • Decay-amplitude weak-phase structure for b → uud : • Time dependent asymmetry probes eff:

  5. Quasi-two-body Analysis R. Aleksanet al, 1990 free Penguin scenario • Quasi-two-body approximation, ignore interference effect • 6 observables through a time-dependent fit: Measure CP violation, but not necessarily phase 

  6. A3 = f+A+ + fA+ + f0A00 A3 = f+A+ + fA+ + f0A00 00 +– + Snyder-Quinn Method Quinn, Snyder PRD 48, 2139, (1993) Idea: Extract  and the strong phases using the interference between B0  +0 amplitudes +0amplitude parameterization: m(0)2 (GeV2) • The f+, ,0 are relativistic Breit-Wigner form factors m(+0)2 (GeV2)

  7. The Square Dalitz Plot Toy MC det|J|

  8. Fit Projection Plots Strong signal with 347M BBbar ρ(770) dominate

  9. Extract physics parameters • Time-dependent Dalitz plot approach should supersede the previous quasi-two-body analysis, with interference among resonances taken into account. hep-ex/0608002 * Using a Q2B approach and 144fb-1 data, BELLE measured:

  10. ρ  =? B0 + ρ+ B0 ρ+ + =? B0  ρ B0 Probing Direct CP Violation Define physically more intuitive quantities: 3.0 Large Direct CPV not expected…

  11. Road to  Dalitz plot specific measurements: • What is the strong phase between B0ρ+ and B0ρ+? • What is ?

  12. Measuring sin2β with Charmless B decay decays are tree and penguin diagrams, with equal dominant weak phases decays are pure “internal” and “flavor-singlet” penguin diagrams High virtual mass scales involved: believed to be sensitive to New Physics Both decays dominated by single weak phase BR~ 10-3 B0J/yK0 Tree: sin2b=0.69±0.03 B0fK0 Penguin: BR~ 10-5 New Physics? 3 ?

  13. Sources of Standard Model Pollution There are many modes that dominantly decay via bs(qq)…but not all modes were created equal There are various estimates for the deviation from sin2β due to SM pollution…most of them expect a larger value! This is ok; still gives sin2b in SM. c,t b s K0 B0 d d d w,p0,r0,h’(?),f0(?)… d b u w,p0,r0,h’(?),f0(?)… B0 u s CKM and color suppressed.. but will lead to slight deviation. K0 d d

  14. sin2β from B0KS Final State • quite a few CP events in this decay including r0KS and f0KS • also a higher (f?) resonance ~1500 MeV • there is a possible tree diagram which contaminates the sin2b measurement • time-dependent CP has been measured for f0Ks and r0Ks Last summer, Belle presented a (time and tag independent) Dalitz Plot analysis of this mode…this approach will be important in the future!

  15. B0KS Final State • A Dalitz plot with rich structures, apart from CP eigenstates, there are also flavor eigenstates. • K*(890)π, K*0(1430)π are important for testing QCD factorization and other schemes. • Can look for direct CP violation and test SU(3) symmetry in the B→ PV decays • Interference with flavor eigenstates can help lift the degeneracy in the sin2β measurement K*(890) K*(1430)

  16. B0f0KS ML fit : • Systematic errors dominated by • Fit bias & interference with other modes

  17. B0ρ0 KS • Complications • high level of bkg • ρ is broad • Interference with ππ s-wave at both high mass and low mass BaBar: S=0.17±0.52±0.26 C=0.64±0.41±0.25

  18. Analysis of B0KS Dalitz Plot Similar analysis technique, need to handle additional flavor eigenstates f0 r0 f??? Strong signal with 347M BBbar

  19. Conclusion • Extraction of α from B ρπ • The isospin analysis appears hopeless for the near future • There is hope for the Dalitz plot analysis although it’s technically difficult. • Extract α with no ambiguities. Especially useful when combined with other experiments or other measurements of α. • Latest result in hep-ex/0608002 • Pioneered time-dependent Dalitz plot analysis for B decays. Framework setup to study other three-body B decays. • Already tested on B0→K+–0 • Close to finish CP measurement of B0→K0+–,where CP violation in s-penguin decay and direct CP violation will be tested • Foresee preliminary results in September.

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