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Results on CP Violation and CKM Unitary Triangle

Results on CP Violation and CKM Unitary Triangle. B-Factories in the World. Data taking finished on Jun.30 th , 2010 ∫ L dt = 1052.79 fb⁻¹. Belle (Japan). BaBar (US). Data taking finished in Apr, 2008 ∫ L dt = 558 fb⁻¹. KEKB Accelerator.

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Results on CP Violation and CKM Unitary Triangle

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  1. Results on CP ViolationandCKM Unitary Triangle Workshop on Synergy betweenHigh Energy and High Luminosity Frontiers

  2. B-Factories in the World Data taking finished on Jun.30th, 2010 ∫Ldt = 1052.79 fb⁻¹ Belle (Japan) BaBar (US) Data taking finished in Apr, 2008 ∫Ldt = 558 fb⁻¹

  3. KEKB Accelerator World highest luminosity2.1x10³⁴cm⁻²s⁻¹ Mt. Tsukuba World highest integrated luminosity 1052.79 fb⁻¹ e⁻ 8.0GeV IR e⁻ 3km incircumference e⁺ e⁺ 3.5GeV KEK History of the integrated luminosity

  4. Belle Detector γ and e± energy • Electromagnetic Calorimeter • CsI (Tl) crystal. • Energy measurements of γ and e±. • @ 1 GeV. Particle species • KLμ Detector • Sandwich of 14 RPCs and 15 iron plates. • μ-ID with iron-punch-through power. • Return path of magnetic flux. 3.5GeV e⁺ Particle species • Time-of-Flight Counter • Plastic scintillation counter. • K/π-ID of high range p. • Time resolution ~100 ps. 8.0GeV e⁻ Particle species • AerogelČerenkov Counter • Refractive index n=1.01-1.03. • K/π-ID of middle range p. Charged particle momentum • Central Drift Chamber • 8,400 sense wires along the beam direction. • Momentum resolution • PID with dE/dx measurement. • 1.5 T magnetic field. • Silicon Vertex Detector • Four detection layers. • Vertex resolution~ 100 μm. B decay position

  5. History of Belle • Dec.,1998 Detector construction had completed. • Jan.,1999 Cosmic-ray event taking had started. • Feb.,1999 The first e+-e– collision of KEKB. • May.,1999 The detector had been rolled in to the IR. • Jun.4th,1999 The first physics event. … • 9:00am Jun.30th,2010 Data taking finished.

  6. End Run Ceremony I was here. The e+/e– beams wereaborted by A. Suzuki, thedirector general of KEK. Collaborators’ snapshot at the run end:

  7. CKM Matrix and Unitarity Triangle Wolfenstein Parameterization KM ansatz:Irreducible complex phases (in Vub and Vtd inWolfenstein parameterization) cause the CP violation. One of the unitarity conditions: iη Unitarity condition forms a untarity triangle in the complex plane. (φ₁, φ₂, φ₃) = (β, α, γ) ρ O

  8. _ B0-B0 Mixing and Mixing-Induced CPV _ _ V*tb Vtd b d _ t B⁰ B⁰ ~ Vtd² ~ e⁻²iφ₁ W W t d b Vtd V*tb _ B⁰ andB⁰mix with each other through a box diagram shown above. _ Even if B⁰ andB⁰ decay to the same final state, the phase of the decayamplitude may differ depending on the B flavor at the decay time. B⁰ fCP phase == 0 interference _ B⁰ B⁰ fCP phase difference = 2φ₁ CPV due to the interference is called“mixing-induced CP violation”.

  9. CP Violation in Proper-Time Distribution The e⁺-e⁻ collision produces a pair of B mesons through bb resonance. • The mixing-induced CP violation manifests itself in the signed time duration “Δt = tBCP – tBtag”, where • tBCP … time when one B decays to the CP eigenstate. • tBtag … time when the other B decays to the flavor-specific state. S = 0.65 A = 0.00 Btag = B0 Btag = B0 _ Δt (ps)

  10. Reconstruct fCP (J/ψKS⁰ …) Analysis Method π⁺ ℓ⁺ π⁻ Silicon Vertex Detector ℓ⁻ KS⁰ Silicon Vertex Detector Beam pipe J/ψ B⁰ Determine proper-time differenceΔtof the two B mesons Determine S(= sin2φ₁) using the event-by-eventqandΔt e⁺-e⁻collision 3.5GeV 8.0GeV e⁻ e⁺ Δt _ B⁰ Determine the B meson flavor q opposite to the one decayed tofCP D⁺ Silicon Vertex Detector π⁺ K⁻ π⁻ Silicon Vertex Detector π⁺

  11. B⁰ J/ψK⁰: Golden Modes for φ₁ _ _ bccs tree _ _ c J/ψ b The decay diagram includesneither Vub nor Vtd.  The φ₁ is accessible. c B⁰ W _ s d K⁰ d • The B⁰ J/ψK⁰ is mediated by bccs tree transition. • SM prediction: S = –ηCPsin2φ₁, A≈ 0 • Test of Kobayashi-Maskawa theory.  Nobel prize in 2008 • Check for a NP phase with very precise unitarity tests.

  12. B⁰ J/ψK⁰ Reconstruction BCPJ/ψKS⁰ BCPJ/ψKL⁰ • data • MC: signal • MC: J/yKLX Nsig = 7482 Purity = 97 % ηCP = –1 • MC: J/yX • MC: comb. Events / 50 MeV/c Events / 1 MeV/c² Nsig = 6512 Purity = 59 % ηCP= +1 BCPmass (GeV/c²) BCPmomentum in the cms(GeV/c) Gaussian Gaussian Event-by-event S/N isobtained from an MC simulation. ARGUS func. slope peak @ 0 GeV peak @ 5.28 GeV/c² _ Event-by-event S/N isobtained from the model above. 535M BB

  13. _ S and A from BJ/ψK⁰ (535M BB) Phys. Rev. Lett. 98, 031802 (2007). Brec = J/ψKS⁰ + J/ψKL⁰ (stat) (syst) Dominant systematic error sources

  14. _ S and A Update (772M BB) _ from 772 x 10⁶BB pairs = final Belle data sample _ ccKS⁰ J/ψKL⁰ Belle preliminary We have more yields than the NBB increase, for we have improved the track finding algorithm.

  15. Latest Status of S and A Measurements _ • We are finalizing the S and A in bccs modes using the full data set. • Preliminarily expected statistical sensitivity • Predicted by a signal-yield scale applied to the ICHEP2006 results. • The statistical uncertainties are getting close to the systematic ones.

  16. _ bsqq Time-Dependent CP Violation _ _ _ _ bccs tree bsqq penguin _ _ W c _ _ J/ψ b s b φ, f₀… c t g B0 W B0 s _ _ s d d s K⁰ K⁰ d d S = sin2φ₁, A ≈ 0 S = sin2φ₁eff, A ≈ 0 In case of an extra CP phasefrom NP in the penguin loop Deviation of bsqqCP-violating parameter from bccs indicates NP in the penguin loop

  17. Interference in B⁰KS⁰K⁺K⁻ Final State Dalitz plot φKS⁰CP = –1 Dalitz-plot φKS⁰ A₁ f₀(980)KS⁰ f₀(980)KS⁰CP = +1 A₂ s₋ = M²(K⁻KS⁰) B⁰ KS⁰K⁺K⁻ Non-resonant Non-resonant AN Others … s₊ = M²(K⁺KS⁰) • B⁰KS⁰K⁺K⁻ final state has several different paths. • Fit to the Dalitz plot is need for the correct CPV measurement.

  18. Interference in B⁰KS⁰K⁺K⁻ Final State _ Dalitz plot B⁰-B⁰mixing φKS⁰CP = –1 Dalitz-plot φKS⁰ A₁ f₀(980)KS⁰ f₀(980)KS⁰CP = +1 A₂ s₋ = M²(K⁻KS⁰) B⁰ KS⁰K⁺K⁻ Non-resonant Non-resonant mixing AN _ Others … B⁰ s₊ = M²(K⁺KS⁰) • B⁰KS⁰K⁺K⁻ final state has several different paths. • Fit to the Dalitz plot is need for the correct CPV measurement.

  19. Interference in B⁰KS⁰K⁺K⁻ Final State _ + Dalitz plot B⁰-B⁰mixing  CPV measurement φKS⁰CP = –1 Dalitz-plot φKS⁰ A₁ f₀(980)KS⁰ f₀(980)KS⁰CP = +1 A₂ s₋ = M²(K⁻KS⁰) B⁰ KS⁰K⁺K⁻ Non-resonant Non-resonant mixing AN _ Others … B⁰ s₊ = M²(K⁺KS⁰) • B⁰KS⁰K⁺K⁻ final state has several different paths. • Fit to the Dalitz plot is need for the correct CPV measurement.

  20. B⁰KS⁰K⁺K⁻ Reconstruction ΔE signal continuum other B Mbc _ from 657 x 10⁶BB pairs • # of reconstructed events • Estimation by unbinned-maximum-likelihood fit to the ΔE-Mbc distribution • B⁰KS⁰K⁺K⁻ Nsig = 1176±51 • Reconstruction efficiency ~16% • Background • Continuum ~ 47% • Other B decays ~ 3% • Signal purity ~ 50%

  21. CPV Measurement in B⁰KS⁰K⁺K⁻ • The (φ₁, A) are determined by an unbinned-ML fit onto the time-dependent Dalitz distribution. • The signal probability density function: • Four parameter convergences from the fit • They are statistically consistent with each other. • Which is the most preferable solution?

  22. CPV Measurement in B⁰KS⁰K⁺K⁻ Intermediatestate-by-state fraction • Solution #1 is most preferred from an external information. • The Br(f₀(980)π⁺π⁻)/Br(f₀(980)K⁺K⁻) favors solutions withlow f₀(980)KS⁰ fraction, when compared to the PDG. • The Br(f₀(1500)π⁺π⁻)/Br(f₀(1500)K⁺K⁻) favors solutions withlow f₀(1500)KS⁰ fraction, when compared to the PDG. • Here, we assumefX as f₀(1500).

  23. CPV Measurement in B⁰KS⁰K⁺K⁻ Y.Nakahamaet al., Phys. Rev. D 82, 073011 (2010) [solution #1] Only in the φmass region Only in the φmass region SM prediction BG _ 657 x 10⁶ BB pairs The third error accounts for an uncertainty arises from Dalitz model.

  24. CP Violation in bs Penguin B⁰ φK⁰, η’K⁰ (bs) B⁰ J/ψK⁰ (bc) 0.8σdeviation • Latest tension in between tree and penguin • Sbc=SbsSM • W.A.: Sbs = 0.64±0.04 • W.A.:Sbc= 0.673±0.023 • Prospect • δ(Sbs) ~ 0.012 @ 50ab–1

  25. Measurement of φ₂ • φ₂ can be measured using B⁰π⁺π⁻, ρ⁺ρ⁻ decays. tree penguin _ W _ _ d _ W d π⁺, ρ⁺ b b t g π⁺, ρ⁺ u B⁰ B⁰ u _ _ d u u d π⁻, ρ⁻ π⁻, ρ⁻ d d If no penguin contribution …  In presence of penguin, (θ can be given from the isospin analysis.)

  26. Extraction of φ₂ from Isospin Analysis S = … A = … Complex amplitude: A • B ππ branching fraction • Bππ DCPV parameters _ Input φ₂can be solved _

  27. _ S and A from B⁰ π⁺π⁻, ρ⁺ρ⁻ (535M BB) B⁰ π⁺π⁻ B0ρ⁺ρ⁻ H.Ishinoet al.,Phys. Rev. Lett. 98, 211801 (2007) A.Somovet al.,Phys. Rev. D 76, 011104(R) (2007)

  28. Constraint on φ₂ J.Charles et al. [CKMfitter Group], Eur. Phys. J. C41, 1 (2005).

  29. KπPuzzle in B⁰/B⁺CPViolation _ B⁰ K⁻π⁺ B⁰ K⁺π⁻ B⁰ 5.3σ deviation Hint of NP S.-W. Lin et al. (The Belle collaboration), Nature 452, 332 (2008). B⁻K⁻π⁰ B⁺ K⁺π⁰ B⁺ T P Diagrams contributingto both B⁰ and B⁺ Diagrams contributingonly to B⁰ and B⁺ PEW C PEW contribution to CPVis large due to NP…?

  30. KπPuzzle in B⁰/B⁺CPViolation Four precise measurements of CP-violating parameters related to the Kπ and the “sum rule” will give the answer. 0.14± 0.13 ± 0.06@ 600 fb⁻¹ (Belle) CPV in K⁰π⁰ is statistically difficult to measure  Need for SuperKEKB. Present 50 ab⁻¹ Sum Rule Significant deviation may be seen with 10 ab⁻¹data. • Prospect • 10ab–1 data may conclude the existence of NP

  31. Direct CP Violation in B⁺ J/ψK⁺ 31 NEW!! Previous measurementsof ACP(B⁺ J/ψK⁺) [%] Belle –2.6±2.2±1.7 Phys. Rev. D67, 032003 (2003) BABAR +3.0±1.4±1.0 Phys. Rev. Lett. 94, 141801 (2005) D0 +0.75±0.61±0.30 Phys. Rev. Lett. 100, 211802 (2008) W/A +0.9±0.8 (PDG2009) Tree Penguin • Physics motivation • The B⁺ J/ψK⁺decay mediated by the bsu-penguin has a different weak phase from the tree. • The interference between the tree and penguin can cause the direct CP violationin B⁺ J/ψK⁺.

  32. Raw Asymmetry in B⁺ J/ψK⁺ • For K±(average), 80.5% K efficiency and 9.6% π fake rate. K-π likelihood ratio Yield: 41188±205 Mean: 5279.28±0.01 MeV/c² Width: 2.69±0.01 MeV/c² ΔE region: |ΔE|< 40 MeV _ Signal = single Gaussian Background = ARGUS BG Peaking BG is negligibly small  systematic uncertainty. 772 x 10⁶ BB pair data • B±J/ψK±event reconstruction • B± candidates are reconstructed from J/ψ and K±. • Raw asymmetry: ACPraw • Measured raw asymmetry, which still includes K⁺/K⁻ charge asymmetry in detection, is: ACPraw = (–0.33±0.50)% • The “raw asymmetry” is obtained from yields of the B⁺ J/ψK⁺ andthe B⁻ J/ψK⁻in a signal region.

  33. K⁺/K⁻ Charge Asymmetry • K⁺/K⁻ charge asymmetry in detection: AεK⁺ • The K+/K– charge asymmetry in detection arises due to • Non-symmetric detector geometry, • Different interaction rates in material of K⁺/K⁻, and • Different KID efficiencies of K⁺/K⁻. • The raw asymmetry ACPraw should be corrected for by theK⁺/K⁻ charge asymmetry AεK⁺.

  34. K⁺/K⁻ Charge Asymmetry Estimation 34 assuming • The K⁺/K⁻ charge asymmetry depends on the cosθKlaband pKlab. We bin the signal regions in the (cosθKlab, pKlab) plane into 10 boxes, and measure the charge asymmetry for each bin. Real data #10 #1 Each box corresponds toone of the 10 signal bins. • K⁺/K⁻ charge asymmetry estimation • The K⁺/K⁻detection asymmetry is estimated usingthe Ds⁺ φ[K⁺K⁻]π⁺ and D⁰K⁻π⁺, and their charge conjugate. • Estimated K⁺/K⁻ charge asymmetryin detection (averaged over bins) is:AεK⁺ = (–0.43±0.07±0.17)%

  35. CP Violation Measurement in B⁺ J/ψK⁺ 35 K.Sakai et al., Phys. Rev. D82, 091104(R) (2010). _ 772 x 10⁶ BB pairs • Fit result • From the sum of ACPraw and AεK⁺, we preliminarily determine • We observe no significant CP violation in B⁺ J/ψK⁺.

  36. Unitarity Triangle Opened? Unitarity triangle opened? • Prospect • 50ab–1data may conclude the real unitarity

  37. Summary _ _ • Following items have been presented: • Mixing-induced CPV (φ₁) measurement in bccs • Mixing-induced CPV measurement in bsqq • Mixing-induced CPV (φ₂) measurement in B⁰ π⁺π⁻, ρ⁺ρ⁻ • KπPuzzle in B⁰/B⁺CPviolation • Direct CPV in B⁺ J/ψK⁺ • Prospect of unitarity check by Belle II

  38. Backup Slides

  39. Reconstruction of Δt • Δt: proper-time difference of the two B mesons • The Δtis calculated from a Δz: displacement ofdecay vertices of the two B mesons. • Decay vertex reconstruction • Assume all decay tracksgoesthrough a commonpoint (vertex). • Minimizes • The Vi is the i-th inverse error matrix. • RMS of the vertex resolutionis ~ 120 μm j-th track i-th track δhj δhi vertex decay products vertex B

  40. Δt Resolution Function K π D* Btag ℓ secondary tracks true vertex reconstructed vertex primary tracks • One of dominant systematic error sourcesto the S/A • Convolution of the following 4 components • Detector resolution… modeled byσandχ²of the vertex fit. • Secondary track effect of Btag decay… modeled by exponential. • Higher priority is given to the ℓ of the BtagD*ℓνdecay. • Effect from... exactly calculated. • “Outlier” component... Gaussian with σ ~ 10τB⁰.

  41. Determination of BtagFlavor r = q(1–2w) _ _ Btag= B0 Btag= B0 –1 0 +1 Achg unambiguous no info. unambiguous |Δt| (ps) • Memory lookup method • Assign flavor to Btagdecay products track-by-track referring the MC-generated lookup table • Combine the track-by-track flavors and get flavor of the event. • Determine Btag flavor(q:±1)and its ambiguity (w:0…1). • Calibration of MC-originatedw • The w is calibrated using B⁰-B⁰ mixing.

  42. Unbinned-Maximum Likelihood Fit Δt resolution wrong tagging probability background contamination Btag = B⁰ Btag = B⁰ Btag = B⁰ Btag = B⁰ _ _ wrong tagging probability Δt resolution  background CPV-parameter determination from the UML fit

  43. B⁰KS⁰K⁺K⁻ CPVSystematic Uncertainty for the solution #1 List of the systematic-uncertainty sources

  44. B⁺ J/ψK⁺ Reconstruction Tightly identified edE/dx && EECL/p && ECL shower shape Tightly identified μ# of penetrating iron plates && shower Loosely identified edE/dx || EECL/p Loosely identified μ EECL ≈ E deposit by MIP e⁺e⁻ μ⁺μ⁻ tight + loose tight + tight tight + loose tight + tight • B±J/ψK±event reconstruction: J/ψ • J/ψ candidates are reconstructed from e⁺e⁻ or μ⁺μ⁻ pairs. • (Tightly identified lepton) + (tightly or loosely identified lepton). 2.947 < Mee < 3.133 GeV/c² 3.037 < Mμμ < 3.133 GeV/c²

  45. B⁺ J/ψK⁺CPV Systematic Uncertainty 45 List of the systematic-uncertainty sources

  46. CP Violation Measurement in B⁺ J/ψK⁺ List of bin-by-bin CP violation and charge asymmetry

  47. SuperKEKBAccerelator x40 luminosity of KEKB L = 2x10³⁵cm⁻²s⁻¹ IR Better “squeezing” magnet [NEG Pump] 4.0GeV e⁺ SuperKEKB 7.0GeV e⁻ Beam [SR Channel] Improvementsin the RF components SR Improvements in beam pipe [Beam Channel] Installation ofdamping ring

  48. Belle II Detector Time-of-propagation counter Central drift chamberSmaller cell, longer lever arm Ring image Čerenkovcounter Fast data acquisition system Intelligenthardware trigger Larger mass storage system 2-layerDEPFET pixel4-layer DSSD KLμdetector Barrel part: RPCEndcap part:scintillator+ SiPM Electromagnetic calorimeterBarrel part: CsI(Tℓ)Endcal part: pureCsI

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