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Flavor oscillation and CP violation Quark mixing and the CKM matrix Flavor oscillations: Mixing of neutral mesons CP violation Neutrino oscillations. 1. CKM Matrix. Unitarity. mass eigenstates. weak eigenstates. CKM matrix. Charged currents:. mass/ flavor. weak.

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Flavor oscillation and CP violation Quark mixing and the CKM matrix


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    1. Flavor oscillation and CP violation • Quark mixing and the CKM matrix • Flavor oscillations: Mixing of neutral mesons • CP violation • Neutrino oscillations

    2. 1. CKM Matrix Unitarity mass eigenstates weak eigenstates CKM matrix Charged currents: mass/ flavor weak

    3. parameter (9 complex elements) • -5 relative quark phases (unobservable) • -9 unitarity conditions • =4 independent parameters: 3 angles + 1 phase PDG parametrization 3 Euler angles 1 Phase 1.1 Parameters of CKM matrix Number of independent parameters:

    4. Unobservable Phases Phases of left-handed fields in Jcc are unobservable: possible redefinition Real numbers Under phase transformation: 5 unobservable phase differences !

    5. d s b u C t Magnitude of elements komplex in O(3) , A, , , = 0.22 Wolfenstein Parametrization Reflects hierarchy of elements in O()

    6. CP (T) violation i.e. Complex elements Complex CKM elements and CP violation CP T Remark: For 2 quark generations the mixing is described by the real 2x2 Cabbibo matrix  no CP violation !!. To explain CPV in the SM Kobayashi and Maskawa have predicted a third quark generation.

    7. 2. Mixing of neutral mesons As result of the quark mixing the Standard Model predicts oscillations of neutral mesons: Similar graphs for other neutral mesons: Neutral mesons: 1987 1960 2007 2006 discovery of mixing

    8. For neutral mesons consider 2 components M and Γhermitian: 2.1 Phenomenological description of mixing Schrödinger equation for unstable meson:

    9. Neutral B mesons Mass eigenstates (by diagonalizing matrix) Parameters of the mass states Heavy and light mass eigenstate: complex coefficients Flavor eigenstates

    10. Time evolution “Generic particle” ( PH,L )

    11. Time evolution of neutral meson states No mixing part: CPT With mixing:

    12. For  very small: H  L   (e.g. B0)

    13. Two mixing mechanisms: • Mixing through decays • Mixing through oscillation show different oscillation behavior CP, T- violation in mixing: In general:

    14. „long distant, on-shell states“ „short distant, virtual states“ For K0 important, for B0 negligible Mixing mechanisms: e.g. K0

    15. KL and KScan be identified with the mass eigenstates (ignoring CP violation) Phase convention: Large differences between lifetimes 2.2 Neutral kaons Observation of two neutral kaons KL (long) and KS(short)with different lifetimes:

    16. Neutral kaon system After the lifetime of the Ks the K0 consists entirely out of Kl’s, which are essentially an equal mixture of K0 and K0. Expectation Initially pure K0 beam Measurement self-tagging CPLEAR

    17. K0 - K0 (strangeness) oscillation in the SM Long range effects: difficult to calculate Short range effects Oscillation frequency m: c quark contribution dominant: although mt2 is very large, the factor |VtsVtd|2 ~ 5 is very small !

    18. Mixing mechanisms: • Mixing through decay: many possible hadronic decays   is large  Significant contribution only from top loop • Mixing through oscillation Large ms,d: ms~1/2 md  Bs osc. is about 35 times faster than Bd osc. 2.3 Neutral B Meson

    19. ARGUS 1987 Discovery of B0 mixing First e+e- B factory at DESY: Unmixed: Mixed: Same charge

    20. Mixing of neutral B mesons

    21. Observation: Spring 2006 D0 5 Messung (CDF Collaboration, September 2006) 35 times faster than B0

    22. 3. CP violation in the K0 and B0 system forbidden allowed forbidden • C and P violated in weak decays • CP conserved in weak interaction ?  No !

    23. Phase convention: 3.1 Observation of CP violation (CPV) in KL decays Reminder: If no CPV:

    24. If no CPV: Christenson, Cronin, Fitch, Turlay, 1964 should always decay into 3: CP(|3>)= -1 and never into 2 CP(|2>)= +1 Explanation: Not a CP eigenstate: CP violation !

    25. 1999 After 35 years of kaon physics: (mixing) (Direct CPV) Interpretation of CPV measured in the kaon system is difficult. Much easier to understand and to predict in the SM is the B meson system: CPV in the B0 system was observed in 2000.

    26. Phase angle0: complex CKM matrix Different mixing for quarks and anti-quarks Origin of CP Violation (CPV) Antiquarks: 3.2 CP Violation in the Standard Modell see Wolfenstein parametrization Quarks:

    27. Strength of CPV: Characterized by Jarlskog invariant In SM:  6 “triangle” relations in complex plane: Unitary CKM matrix: VV† = 1  area = J/2   Important for Bd and Bs decays

    28.   Rescaled unitarity condition Im Re 0 1

    29.  Phase measurement  Interference experiment 3.3 Observation of CP Violation Weak and CP invariant phase difference Need two phase differences between A1 and A2: Weak difference which changes sign under CP and another phase difference (strong) which is unchanged.

    30. weak strong 2 2  q/p p/q  “3 Ways” of CP violation in meson decays a) Direct CP violation b) CP violation in mixing

    31. c) CP violation through interference of mixed and unmixed amplitudes Asymmetrie modulated by Combinations of the 3 ways are possible!

    32. B0 B0 g Ad a) Direct CP violation (B system) Strong phase difference CP Asymmetrie

    33. 4.2s PRL93(2004) 131801.

    34. b) CP (T) violation in mixing T violation Reminder: Skipped. Measured using semileptonic decays

    35. Standard model prediction for B CPLEAR B0B0 System: K0K0 System: HFAG 2004 Skipped.

    36. CP=-1 c) CP violation in interference between mixing and decay

    37. K0 mixing B0 decay B0 mixing c s d b d b c W+ s s d d b d d SM prediction of CP for B0→J/Ks Same for all ccK0 channels Beside Vtd all other CKM elements are real no direct CPV, no CPV in mixing

    38. Interference = sin2 for B0J/KS indicates direct CP violation if |q/p|1 Calculation of the time-dependent CP asymmetry negligible Time resolved

    39. To measure CP violation in Bd system: • Need many B (several 100  109) • Need to know the flavor of the B at t=0 • Need to reconstruct the decay length to measure t

    40. 50% / 50% 3.4 Measurement of sin2: Asymmetric e+ e- B factory Symmetric: B mesons decay at rest  decay length z0 Asymmetric: decay length z250m Boost  = 0.56

    41. Measurement of sin2: Coherent oszillation (4s) Ereignisse

    42. PRL 94, 161803. • B0D*+p-fast • D0p+soft • K-p+ B0(Dt) (2S) Ks m+m- p+p- Measurement of sin2: Golden decay channel

    43. 3.5 Experimental status of the Unitarity Triangle • Standard Model CKM mechanism confirmed • Large CP Violation in B decays • Large direct CP violation observed • CPV parameter related to magnitude of non-CP observables A triple triumph

    44. No No • CP violation in quark sector is a factor ~1010 to small. • for MHiggs> 114 GeV: Symmetry breaking = 2nd order phase transition 3.6 Baryon asymmetry in the universe Does the Standard Model explain the baryon symmetry in universe? Andrei D. Sakharov, 1967 • Baryon number violation • C and CP Violation • Departure from thermal equilibrium Attractive: Super-symmetric extensions of Standard Model • Additional CP violation through supersymmetric particles • Extended Higgs-sector  strong phase transition Alternative: Lepto-genesis

    45. New Physics W New Physics W 3.7 Flavor and CP Physics as probe for New Physics Aim: Search for New Physics in loop-processes Penguin amplitudes Box-Diagramms (oscillation) Deviation from the Standard Model Absolute rates und phase dependent CP asymmetries Complementary to the direct searches for NP by ATLAS/CMS Historical examples: GIM Mechanism, B Oscillation

    46. Bs Future searches for New Physics Bs mixing (new phases): (visible) CP Violation in penguin decays: (visible) (visible) Precision meas. of CKM Phase : Tree Zerfälle: Loop Zerfälle: Rare deacys: T. Hurth

    47. LHCb – B Physics at the LHC

    48. bb Produktion b p p inel~ 80 mb bb~ 500 b qb qb b B Meson Production at the LHC Gluon-Gluon-Fusion: • LHC • pp Kollisionen bei s = 14 TeV • Korrelierte Vorwärtsproduktion der bb • für L ~ 2 x 1032 cm-2s-1 (defokussierte Strahlen am LHCb IP): • n = 0.5 IA / BX (ATLAS 5…25) • ~1012 bb Ereignisse/Jahr • LHCb • Ein-Arm Vorwärtsspektrometer 12 mrad <  < 300 mrad(1.8<<4.9)

    49. Typisches B Ereignis in LHCb Simuliertes Ereignis • Zerfallslänge L typisch ~ 7 mm • Zerfallsprodukte p ~ 1–100 GeV • Trigger auf “low pt” Teilchen (wie Untergrund) • Physik verlangt Rekonstruktion des Zerfalls alle 25 ns

    50. Massive neutrinos develop differently in time. for masses mi<<Ei:  there will be a mixing of the flavor states with time. 4. Neutrino Oscillations For massive neutrinos one could introduce in analogy to the quark mixing a mixing matrix describing the relation between mass and flavor states: Constant for massless : mixing is question of convention