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K. Honscheid Dept. of Physics Ohio State University

a. g. b. New Results from the BaBar Experiment. Part 1: Matter-Antimatter Asymmetry. Part 2: CP Violation and the SM. Part 3: Beyond the Standard Model. K. Honscheid Dept. of Physics Ohio State University. Matter, Energy and the Big Bang.

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K. Honscheid Dept. of Physics Ohio State University

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  1. a g b New Results from the BaBar Experiment Part 1: Matter-Antimatter Asymmetry Part 2: CP Violation and the SM Part 3: Beyond the Standard Model K. Honscheid Dept. of Physics Ohio State University K. Honscheid, WSU Apr. 15, 2005

  2. Matter, Energy and the Big Bang • Einstein showed us that matter and energy are equivalent • When matter and antimatter meet, they annihilate into energy • Energy can also materialize as particle-antiparticle pair Predict: nMatter/nPhoton~ 0 Exp: nb/ng~ (6.1 +/- 0.3) x 10-10 (WMAP) K. Honscheid, WSU Apr. 15, 2005

  3. So how can this happen? In 1967, A. Sakharov showed that the generation of the net baryon number in the universe requires: • Baryon number violation(Proton Decay) • Thermal non-equilibrium • C and CP violation(Asymmetry between particle and anti-particle) Transition to broken electroweak symmetry provides these conditions K. Honscheid, WSU Apr. 15, 2005

  4. Experimental Possibilities: • Get equal amounts ofmatter and anti-matter • Wait… • See what’s left(in anything) K. Honscheid, WSU Apr. 15, 2005

  5. PEP-II Asymmetric B Factory Stanford Linear Accelerator Center, Stanford, California K. Honscheid, WSU Apr. 15, 2005

  6. The BaBar Experiment K. Honscheid, WSU Apr. 15, 2005

  7. Preparing the Matter – Antimatter Sample B mesons contain a b quark and a light anti-quark. mB = 5.28 GeV (~5x mProton) The Upsilon(4S) - a copious, clean source of B meson pairs 1 of every 4 hadronic events is a BB pair No other particles produced in Y(4S) decay Equal amounts of matter and anti-matter BB Threshold Collect a few 108 B0 B0 pairs K. Honscheid, WSU Apr. 15, 2005

  8. Analysis techniques Threshold kinematics: we know the initial energy of the system Event topology Signal Signal (spherical) Background Background (jet-structure) K. Honscheid, WSU Apr. 15, 2005

  9. Searching for the Asymmetry 227 x 106 B0 Mesons CountB0K+Decays 227 x 106 B0 Mesons CountB0K-+Decays Is N(B0K+) equal to N(B0K-+)? K. Honscheid, WSU Apr. 15, 2005

  10. Quartz bar Active Detector Surface Particle Cherenkov light How to Tell a Pion from a Kaon Angle of Cherenkov light is related to particle velocity • Transmitted by internal reflection • Detected by~10,000 PMTs K. Honscheid, WSU Apr. 15, 2005

  11. B0K+ Searching for the Asymmetry 227 x 106 B0 Mesons CountB0K+Decays 227 x 106 B0 Mesons CountB0K-+Decays Is N(B0K+) equal to N(B0K-+)? B0K+ BABAR background subtracted BABAR K. Honscheid, WSU Apr. 15, 2005

  12. Direct CP Violation in B Decays Using We obtain First confirmed observation of direct CP violation in B decays K. Honscheid, WSU Apr. 15, 2005

  13. Part 2: CP Violation in the Standard Model CP Operator: coupling q’ q’ g g* CP( ) = q q J J Mirror To incorporate CP violation g ≠ g* (coupling has to be complex) K. Honscheid, WSU Apr. 15, 2005

  14. l3 l l l2 l3 l2 d s b l=cos(qc)=0.22 u c t The Kobayashi-Maskawa Matrix • The weak interaction can change the favor of quarks and lepton • Quarks couple across generation boundaries • Mass eigenstates are not the weak eigenstates • The CKM Matrix rotates the quarks from one basis to the other Vcb Vub K. Honscheid, WSU Apr. 15, 2005

  15. The Unitarity TriangleVisualizing CKM information from Bd decays d s b u Vud Vus Vub Vcd Vcs Vcb Vtd Vts Vtb • The CKM matrix Vij is unitary with 4 independent fundamental parameters • Unitarity constraint from 1st and 3rd columns: i V*i3Vi1=0 • Testing the Standard Model • Measure angles, sides in as many ways possible • SM predicts all angles are large c t CKM phases (in Wolfenstein convention) K. Honscheid, WSU Apr. 15, 2005

  16. Penguin decay Tree decay g G(B) – G(B) G(B) + G(B) A1 = a1 e -if1 A2 = a2 e-if2eid2 A1 = a1 e-if1eid1 |A|2 – |A|2 |A|2 + |A|2 Understanding CP Violation in B  Kp A1 = a1 eif1eid1 A1 = a1 e if1 B0K-p+ + A2 = a2 eif2eid2 B0K+p- + include the strong phase (doesn’t change sign) more than one amplitude with different weak phase; (A = A1+A2) ~ 2sin(f1 - f2) sin(d1 - d2) = 0 Asymmetry = = K. Honscheid, WSU Apr. 15, 2005

  17. CPV through interference between mixing and decay amplitudes The SM allows B0 B0 oscillations f = b Interference between ‘B  B  fCP’ and ‘B  fCP’ N(B0)-N(B0) N(B0)+N(B0) f = b B0 B0 Mixing and CP Violation A neutral B Meson Mixing frequency Dmd 0.5 ps-1 B0 fraction ~ sin(DmdDt) K. Honscheid, WSU Apr. 15, 2005

  18. Amplitude of CP asymmetry B0 mixing K0 mixing Quark subprocess Time-Dependent CP Asymmetries c b c CP Eigenstate:hCP = -1 W+ B0 s d d K. Honscheid, WSU Apr. 15, 2005

  19. t =0 Dz = Dt gbc bg =0.56 l - (e-, m -) The two mesons oscillate coherently : at any given time, if one is a B0 the other is necessarily a B0 Dt picoseconds later, the B 0 (or perhaps its now a B 0) decays. In this example, the tag-side meson decays first. It decays semi-leptonically and the charge of the lepton gives the flavour of the tag-side meson : l -= B 0l+ = B 0. Kaon tags also used. (4S) Time-dependent analysis requires B0flavor tagging At t=0 we know this meson is B0 B 0 rec We need to know the flavour of the B at a reference t=0. B 0 B 0 tag K. Honscheid, WSU Apr. 15, 2005

  20. sin 2b B tagged sinDmDt B tagged Step by Step Approach to CP Violation 1. Start with a few x 108 B0 B0pairs (more is better) 2. Reconstruct one B0 in a CP eigenstate decay mode 3. Tag the other B to make the matter/antimatter distinction 4. Determine the time between the two B0 decays, Dt 5. Plot Dt distribution separately for B and B tagged events 6. Extract ACP and sin2b Dt (ps) ACP(Dt) Dt (ps) K. Honscheid, WSU Apr. 15, 2005

  21. (1-2w) sin(2b) w = mis-tag fraction Results: sin 2b and the observation of CP J/yKs and otherb  cc s final states 227 million BB pairs CP = -1 • B  J/ Ks0, Ks0p+p-, p0p0 • B (2S) Ks0 • B c1 Ks0 • B  J/ K*0, K*0  Ks0 • B c Ks0 7730 events CP = +1 • B  J/ KL0 BaBar result: sin2b = 0.722  0.040  0.023 K. Honscheid, WSU Apr. 15, 2005

  22. (r,h) a * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb g (0,0) (0,1) The Unitarity Triangle b [23.3 ± 1.5]o K. Honscheid, WSU Apr. 15, 2005

  23. Tree decay B0B0mixing yKs is not the only CP Eigenstate Access to a from the interference of a b→u decay (g) with B0B0 mixing (b) g a = p - b - g sin2a ACP(t)=sin(2a)sin(DmdDt). K. Honscheid, WSU Apr. 15, 2005

  24. Time-dependent ACP of B0→p+p- Blue : Fit projection Red : qq background + B0→Kp cross-feed BR result in fact obtained from 97MBB K. Honscheid, WSU Apr. 15, 2005

  25. pp pp Kp q Kp Kp q pp Houston, we have a problem B0 p+p- B0  K+p- Penguin/Tree ~ 30% K. Honscheid, WSU Apr. 15, 2005

  26. Tree decay B0B0mixing Penguin decay  The route to sin(2a): Penguin Pollution • Access to a from the interference of a b→u decay (g) with B0B0 mixing (b) g Inc. penguin contribution How can we obtain α from αeff ? Time-dep. asymmetry : NB : T = "tree" amplitude P = "penguin" amplitude K. Honscheid, WSU Apr. 15, 2005

  27. How to estimate |a-aeff| : Isospin analysis • Use SU(2) to relate decay rates of different hh final states (h  {p,r}) • Need to measure several related B.F.s 2|-eff| Difficult to reconstruct. Limiting factor in analysis Gronau, London : PRL65, 3381 (1990) K. Honscheid, WSU Apr. 15, 2005

  28. Using isospin relations and • 3 B.F.s • B0p+p- • B+ p+p0 • B0 p0p0 • 2 asymmetries • Cp+p- • Cp0p0 |a-aeff |< 35° • Large penguin pollution ( P/T ) • Isospin analysis not currently viable in the B→ppsystem Now we need B0→p0p0 • 61±17 events in signal peak (227MBB) • Signal significance = 5.0s • Detection efficiency 25% B±→r±p0 • Time-integrated result gives : K. Honscheid, WSU Apr. 15, 2005

  29. B → rr: Sometimes you have to be lucky P → VV decaythree possible ang mom states: S wave (L=0, CP even) P wave (L=1, CP odd) D wave (L=2, CP even) rhelicity angle We are lucky: ~100% longitudinally polarized! Transverse component taken as zero in analysis PRL 93 (2004) 231801 K. Honscheid, WSU Apr. 15, 2005

  30. very clean tags Time dependent analysis of B→r+r- • Maximum likelihood fit in 8-D variable space 32133 events in fit sample K. Honscheid, WSU Apr. 15, 2005

  31. Searching for B→r0r0 • Similar analysis used to search for r0r0 • Dominant systematic stems from the potential interference from B→a1±p± (~22%) c.f. B→p+p- B.F.= 4.7 x 10-6 and B→p0p0 B.F.= 1.2 x 10-6 B (B→r+r-) = 33 x 10-6 K. Honscheid, WSU Apr. 15, 2005

  32. Isospin analysis using B→rr • The small rate of means • |a-aeff | is small[er] • P/T is small in theB→rrsystem (…Relative to B→ppsystem) • No isospin violation (~1%) • No EW Penguins (~2%) |a-aeff |< 11° K. Honscheid, WSU Apr. 15, 2005

  33. (r,h) * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb g b (0,0) (0,1) The Unitarity Triangle [103 ± 11]o a [23.3 ± 1.5]o K. Honscheid, WSU Apr. 15, 2005

  34. Basic Idea Color suppressed The 3rd Angle: g K. Honscheid, WSU Apr. 15, 2005

  35. First Look at the Data Only a loose bound on rB with current statistics: (rB)2 = 0.19±0.23 BABAR-CONF-04/039 Several other methods are being investigated More data would help a lot… K. Honscheid, WSU Apr. 15, 2005

  36. Combined Experimental Constraint on g BABAR & Belle combined K. Honscheid, WSU Apr. 15, 2005

  37. a * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb b (0,0) The Unitarity Triangle [103 ± 11]o g [23.3 ± 1.5]o [51+20-34]o K. Honscheid, WSU Apr. 15, 2005

  38. Putting it all together • The complex phase in the CKM matrix correctly describes CPV in the B meson system. • Based on SM CPV the baryon to photon ratio in the universe should benb/ng~ 10-20 • Experimentally we findnb/ng~ (6.1±0.3) x 10-10 (WMAP) h r K. Honscheid, WSU Apr. 15, 2005

  39. Part 3: Beyond the Standard Model Part 3: Consistency Checks • FCNC transitions bsg and bdg are sensitive probes of new physics • Precise Standard Model predictions. • Experimental challenges for bdg (Brg Bwg) • Continuum background • Background from bsg (BK*g) (50-100x bigger) Ali et al hep-ph/0405075 K. Honscheid, WSU Apr. 15, 2005

  40. Combined B0r0g,B0wg,B-r-g results • No signals observed @90% CL K. Honscheid, WSU Apr. 15, 2005

  41. CKM constraints from Br(w)g BABAR BF ratio upper limit < 0.029 →|Vtd/Vts| < 0.19 (90% CL) Ali et al. hep-ph/0405075 (z2,DR) = (0.85,0.10) no theory error (z2,DR) = (0.75,0.00) with theory error Penguins are starting to provide meaningful CKM constraint rg95% CLBABAR allowed region (inside the blue arc) K. Honscheid, WSU Apr. 15, 2005

  42. + mixing lCP = -e-2b + mixing lCP = -e-2b + mixing lCP = -e-2b W - t s Vts* Vts* s Vtb Vtb d d W - t d d d d New CP Violating Phases in Penguin Decays? K. Honscheid, WSU Apr. 15, 2005

  43. hep-ex/0502019 preliminary 114 ± 12 events SM 98 ± 18 events Belle [BELLE-CONF-0435] Update on BfKo K. Honscheid, WSU Apr. 15, 2005

  44. Reaching for more statistics – B 0  K 0 revisited • Analysis does not require that ss decays through f resonance, it works with non-resonant K+K- as well • 85% of KK is non-resonant – can select clean and high statistics sample • But not ‘golden’ due to possible additional SM contribution with ss popping • But need to understand CP eigenvalue of K+K-KS: - f has well defined CP eigenvalue of +1, - CP of non-resonant KK depends angular momentum L of KK pair • Perform partial wave analysis • Estimate fraction of S wave (CP even) and P wave (CP odd) and calculate average CP eigenvalue from fitted composition K+K- Nsig = 452 ± 28(excl.  res.) OK Not OK K. Honscheid, WSU Apr. 15, 2005

  45. CP analysis of B  K+K- KS • Result of angular analysis • Result consistent with cross checkusing iso-spin analysis (Belle) • Result of time dependent CP fit hfSK+K-KS/(2fCP-even-1)] = +0.55 ±0.22 ± 0.04 ±0.11 (stat) (syst) (fCP-even) K. Honscheid, WSU Apr. 15, 2005

  46. s d d s s d K0 K0 K0 hep-ex/0502013 More penguin exercises – B0 KS KS KS • Use beam line as constraint and acceptonly KS with sufficient number of SVXhits. • Decay B0 KS KS KS is ‘golden’ penguin – little SM pollution expected • Although 3-body decay, only L=even partial waves allowed: • CP(KSKSKS) = CP(KS) = even • Result consistent with SM Gershon, Hazumi hep-ph/0402097 hfK0 K. Honscheid, WSU Apr. 15, 2005

  47. Same technique as Ksp0 hep-ex/0503011 p - p0 p + KS B0 4mm beam 200mm inflated beam IP-Constrained Vertexing • Constrain decay products to beam-spot in x-y: • Vertex precision depends on number of hits in SVT • For 4 hits, Dt resolution as good as with charged-tracks (60% events) • Crosscheck with J/yKS: K. Honscheid, WSU Apr. 15, 2005

  48. Combined “sin2b” Results Dsin2β~ -2.9 s Dsin2β~ -2.9 s + sin2βPenguin= 0.43 ±0.07 Dsin2β~ -3.7 s …but comparison ignores subleading diagrams ! K. Honscheid, WSU Apr. 15, 2005

  49. penguin u s s Corrections: b→s Decay Amplitude ~ VubVus* Decays involving Vub enter with decay phase g Doubly-CKM suppressed w.r.t dominant diagram Contributes to all b sss modes color-allowed tree color-suppressed tree Contribute to non-resonant KKKs (requires ss popup from soft g) Contribute to h’Ks, f0Ks, wKs, but not fKs [in KKKs (requires ss popup from soft g)] K. Honscheid, WSU Apr. 15, 2005

  50. 2xΔsin2β Adding Theoretical Uncertainties • size of possible discrepancies Δsin2β have been evaluated for some modes: • estimates of deviations based on QCD-motivated specific models; some have difficulties to reconcile with measured B.R. • Beneke at al, NPB675 • Ciuchini at al, hep-ph/0407073 • Cheng et al, hep-ph/0502235 • Buras et al, NPB697 • Charles et al, hep-ph/0406184 • model independent upper limits based on SU(3) flavor symmetry and measured b d,sqqB.R. • [Grossman et al, PRD58; Grossman et al, PRD68; Gronau, Rosner, PLB564; Gronau et al, PLB579; Gronau et al, PLB596; Chiang et al, PRD70] ‘naive’ upper limit based on final state quark content, CKM (λ2) and loop/tree (= 0.2-0.3) suppression factors [Kirkby,Nir, PLB592; Hoecker, hep-ex/0410069] K. Honscheid, WSU Apr. 15, 2005

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