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CP violation in B → pp , rp

CP violation in B → pp , rp. Hiro Sagawa (KEK) FLAVOR PHYSICS & CP VIOLATION, Ecole Polytechnique, Paris, France on June 3-6, 2003. Outline. CP asymmetries in B 0 → p + p - decay CP violating parameters : S pp and A pp (= - C pp )

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CP violation in B → pp , rp

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  1. CP violation in B→pp, rp Hiro Sagawa (KEK) FLAVOR PHYSICS & CP VIOLATION, Ecole Polytechnique, Paris, France on June 3-6, 2003

  2. Outline • CP asymmetries in B0→p+p-decay • CP violating parameters : Spp and App(= -Cpp) • Belle: hep-ex/0301032 ( to be appeared in PRD ) • BaBar: Phys. Rev. Lett. 281802 • Bound onPenguin Pollutionfromisospin relation (B→p+p-,p-p0 , andp0p0 decays ) • CPasymmetries in B0→rp decay (p+p-p0) • Quasi-two-body analysis • BaBar : update atRecontres de Moriond 2003 Belle BaBar

  3. Introduction

  4. Introduction Quark mixing is described by the 3x3 Cabibbo-Kobayashi-Maskawa (CKM) matrix. (Wolfenstein parametrization) One irreducible complex phase derives CP violation . B pp, rp f2(a) Unitarity triangle f3(g) f1(b)

  5. CP violation in mixing and decay CP violation in neutral B meson results from the interference between decays with and without mixing.

  6. q= +1 for B0 tag 1 for B0 tag Time evolution in B0 π+π– Dt=Dz/(bgc) (Belle)

  7. CP violation inB0 π+π– mixing b d B0 t t B0 d b decay Penguin(P) Tree(T) u B0 p+ d b p+ d W+ t u g b B0 u p- B0 u p- d d d d b

  8. Analysis Procedure

  9. Data sample Event Selection p+p-, rp(p+p-p0 ) : charmless B decays BR ~ 10-5-10-6 : rare decays world average (10-6) Need a lot of data Flavor tagging (HFAG table) Continuum suppression Data sample p+p- Belle 85million BB pairs BaBar 88million BB pairs rp BaBar 89million BB pairs Vertex and Dt

  10. Kinematics:Reconstruction of CP side Event Selection Flavor tagging Kinematics Continuum suppression Signal MC Signal MC Vertex and Dt DE(GeV) Mbc(GeV/c2)

  11. Good K/p separation Event Selection Belle ACC(Aerogel Cherenkov Counter) + CDC dE/dx For the tracks in the momentum range that covers the B0p+p- signal, p effciency = 91% 10.3% of kaons are misidentified as pions. 10.0 0.2% from K- 10.6 0.2% from K+ The effect of asymmetry of this misidentification is negligible for the measurement of App and Spp. Threshold type Flavor tagging Continuum suppression Vertex and Dt

  12. Good K/p separation Event Selection BaBarDIRC (Detector of Internally Reflected Cherenkov light) p/K separation Flavor tagging Continuum suppression Vertex and Dt Cherenkov angle ( , ) is used separately as PDF for maximum likelihood fit. Cherenkov angle for positively and negatively charged tracks

  13. Flavor tagging Event Selection Use flavor specific properties and correlations Flavor tagging Continuum suppression Vertex and Dt

  14. Continuum background Event Selection use kinematics and topology to separate sphericalB decays from jettyqq events Flavor tagging Continuum suppression Vertex and Dt

  15. Continuum suppression B0p+p-for the case of Belle Cut on a likelihood ratio (LR) that combines an event topology variable (SFW) and B flight direction (cosqB ) SFW: Super Fox Wolfram Fisher discriminant using modified Fox-Wolfram moments SFW cosqB LR

  16. Vertex reconstruction Event Selection Example vertices • The same algorithm as that used for sin2f1 meas. • Resolution mostly determined by the tag-side vtx. Flavor tagging Continuum suppression B0 lifetime of control sample 1.5510.018(stat) ps Vertex and Dt (PDG02: 1.542±0.016 ps) Time resolution (rms) 1.43ps

  17. CP asymmetries in B0p+p-

  18. Event reconstruction (Belle) Beam-constrained mass (Mbc) energy difference (DE) (in DE signal region) (in Mbc signal region) B-candidate energy – beam energy (CMS) p+p- Kp Kp p+p- qq continuum other rare B decays

  19. 0 0 -5 -5 5 5 -5 0 5 Large CP Violation is seen ! Fit results (Belle) B0 tag B0 tag LR>0.825 sin term cos term hep-ex/0301032 accepted for Phys. Rev. D sin term

  20. Confidence Regions (Belle) Feldman-Cousins frequentist approach 3.4s CL for CP conservation 1) Evidence for CP violation in B0 π+π– 2) “Indication” of direct CP Violation (App>0)

  21. Constraints on theCKM angle f2(a) f2 |P/T|0.15-0.45 (representative) Theory ~0.3 f123.5deg (=b) (Belle & BaBar combined) f2 (=a) d strong phase difference |P/T|=0.45 78o<f2<152o (95.5%C.L.) d<0 favored

  22. Constraint on r-h PDG2002 + ( Belle f1& f2 ) f2=78o f2=118o f2 f1 f3 f2=152o Belle’s results of f1 and f2 are consistent with other measurements.

  23. mESandDE (BaBar) Phys Rev Lett 89, 281802 (2002) pp-enhancedevents mES DE Kp-enhanced events DE mES

  24. CP asymmetry result (BaBar) Phys Rev Lett 89, 281802 (2002) Projection in signalpp-enhancedevents Asymmetry Events/1ps (App=+0.30)

  25. Fit results (Belle&BaBar) The difference is at 2.2s level. It’s early to say conclusively for the difference. &

  26. Comparison with predictions PQCD Purple regions : PQCD favored Region for each f2 (60o, 100o, 150o)

  27. A bound onq=|f2eff-f2|with an upper limit onp0p0 can constrain on f2 using isospin relation.

  28. A bound onq=|f2eff-f2| • Gronau/London/Sinha/Sinha bound(PL B514, 315 (2001)) q(deg) HFAV table

  29. CP asymmetries in B0rp

  30. CP-Violating Asymmetries in B0 →r+p-,r+K- • Principle: measure a directly, even with penguins using full Dalitz-plot analysis • difficulty • Combinatorics and lower efficiency in three-body topology with p0 • Large backgrounds from misreconstructed signal events and other B decays Need large statistics to extract a cleanly • “quasi-two-body” analysis: • Select the r-dominated region of the p+p-p0 /K+p-p0Dalitz plane (Rejected when .) • Suppression of qq backgrounds • Simultaneous fit for r+p- and r+K-

  31. CP Violation Study in B0 →rπ decay Final statep+p-p0: not a CP eigenstate Basically there are four tree amplitudes:  

  32. B0 →rπ Time-dependence Decay rate distribution

  33. Time-integrated asymmetry: Time evolution includes: direct CP violation → ACP and C = 0 indirect CP violation → S = 0 DC and DS are insensitive to CP violation Q is the r charge rKis self-tagging: Fit for:

  34. B0 →rπ/rK (BaBar)Yields and Charge Asymmetries The results with 89 million BB pairs @2003 Moriond EW Preliminary BR of rp and rK B0 →rπ B0 →rK Charge asymmetry of rp and rK

  35. B0 →rπ/rK (BaBar) : Dt distributions B+continuum background B-related background 2s (or more) from zero

  36. Direct CP violation in B0→rp (0,0)

  37. Comparison with predictions BaBar: Arp = -0.18  0.08  0.03 Crp = +0.36  0.15  0.04 DCrp = +0.28  0.19  0.04 QCDF: Arp = -0.015 Crp = 0.019 DCrp = 0.250 w/ Charming Penguin(CP): Srp = -0.015 Crp = 0.092 DCrp = 0.228 Phys. Rev. D67,094019, 2003

  38. Prospect (B0 →p+π-) dApp dSpp L(fb-1) L(fb-1)

  39. Prospect (B0 →rπ) dArp dCrp L(fb-1) L(fb-1) dSrp L(fb-1)

  40. Summary 2s lines • Measurement of CP asymmetries in B0→p+p- • Still early to say conclusively for the difference. • Measurement of CP asymmetries in B0→rp • Quasi-two-body analysis was performed by BaBar. • Hint of Direct CPV ? (0,0)

  41. end

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