A. Bay Beijng October 20051 Summary 1. Some history 2. Antiparticles 3. Standard Model of Particles (SM) Discrete symmetries, CP violation, Connection

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  • A. Bay Beijng October 20051 Summary 1. Some history 2. Antiparticles 3. Standard Model of Particles (SM) Discrete symmetries, CP violation, Connection with Cosmology Fermionic mass generation mechanism, 4. Why do we think that the SM is not the final word ? 5. How do we produce particles? 6. How do we measure particles ? 7. Conclusions
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  • A. Bay Beijng October 20052 The Standard Model e e u c t d s b Quarks Strong : gluons E.M. : photon Weak : W + W Z INTERACTIONSMATTER e.m. charge [e] 0 1 2/3 1/3 The SM incorporates: QED: photon exchange between charged particles Weak (Flavour-Dynamics): exchange of W and Z QCD: gluon exchange between quarks do not forget antiparticles... ! Spin 1/2 Spin 1
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  • A. Bay Beijng October 20053 Summary of this section Symmetries Parity (P), Charge Conjugation (C) and Time reversal (T) P and C violation Baryogenesis CP & T violation Experiments Conclusion
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  • A. Bay Beijng October 20054 Discrete symmetries Parity: left Charge particle antiparticle conjugation Temporal inversion right
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  • A. Bay Beijng October 20055 Discrete symmetries P and C e.m. interactions are P & C invariant P: (x,y,z) -> (-x,-y,-z). C: charge -> charge. angular momentum, spin.
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  • A. Bay Beijng October 20056 What about T ? If x(t) is solution of F = m d 2 x/dt 2 then x(-t) is also a solution (ex.: billiard balls) Ok with electrodynamics:
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  • A. Bay Beijng October 20057 Parity: (x,y,z) (-x,-y,-z) 1848 L. Pasteur discovers the property of optical isomerism. The synthesis of the lactic acid in the lab gives a "racemic" mixture: N left molecules = N right molecules (within statistic fluctuations) This reflects the fact that e.m. interaction is M (and P) invariant Mirror symmetry Asymmetry =
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  • A. Bay Beijng October 200527 Baryo genesis.5 1) processes which violate baryonic number conservation: B violation is unavoidable in GUT. 2) Interactions must violate C and CP. C violated in Weak Interactions. CP violation observed in K and B decays. 3) System must be out of thermal equilibrium Universe expands (but was the change fast enough ?) Starting from a perfectly symmetric Universe: 3 rules to induce asymmetry during evolution Andrej Sakarov 1967 B(t=0) = 0 B(today)>0
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  • A. Bay Beijng October 200528 Baryogenesis.6 Prob(X qq) = Prob(X qe - ) = (1 - - - Prob(X qq) = Prob(X qe + ) = (1 - Requirement: q ou q e + q ou q e X X 10 27 K... forbidden by CP symmetry ! { X qq - - - X qq CP mirror
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  • A. Bay Beijng October 200529 CP violation K 0 L e e MIRROR CP { CP symmetry implies identical rates. Instead... K 0 L is its own antiparticle K 0 L S. Bennet, D. Nygren, H. Saal, J. Steinberg, J. Sunderland (1967): July 1964: J. H. Christenson, J. W. Cronin, V. L. Fitch et R. Turlay find a small CP violation with K 0 mesons !!! e N e N e N e N + % provides an absolute definition of + charge
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  • A. Bay Beijng October 200530 CP violation experiment
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  • A. Bay Beijng October 200531 K0K0 K0K0 Processes should be identical but CPLear finds that neutral kaon decay time distribution anti-neutral kaon decay time distribution CPLear Other experiments: NA48, KTeV, KLOE factory in Frascati,...
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  • A. Bay Beijng October 200532 CPV in BABAR and BELLE World average (October 2005): S CP = 0.726 0.037 A CP ~ 0, compatible with no direct CPV SM: S CP = sin(2 ) => or 66.3)
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  • A. Bay Beijng October 200533 Origin of CP violation Hamiltonian H = H 0 + H CP with H CP responsible for CP violation. Let's take H CP = gH + g*H where g is some coupling. The second term is required by hermiticity. If under CP: H H that is CP H CP = H then CP H CP CP = CP (gH + g*H ) CP = gH + g*H CP invariance : H CP = CP H CP CP gH + g*H = gH + g*H The conclusion is that CP is violated if g g* i.e. g non real CP violation is associated to the existence of phases in the hamiltonian.
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  • A. Bay Beijng October 200534 CKM matrix CPV implies that some of the V ij complex. In 1972 Kobayashi & Maskawa show that, in order to generate CP violation (i.e. to get a complex phase), the matrix describing the weak decays of the quarks must be (at least) 3x3 this is a prediction of the three quark families of the SM: (u, d), (c, s), (t, b) V CKM = In the SM, with 3 and only 3 families of quarks, the matrix must be unitary The last quark, t, was observed 25 years later ! Cabibbo s u W VusVus
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  • A. Bay Beijng October 200535 CKM matrix in the SM L = L W,Z + L H + L Fermions + L interaction L Fermions contains the (Yukawa) mass terms: M U and M D complex matrices, diagonalized by a couple of non-singular matrices, to get the physical mass values:
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  • A. Bay Beijng October 200536 CKM matrix.2 After the transformation (idem for D quarks) e.m. and neutral currents unaffected. The charged currents are modified: "mixing matrix" V unitary s u W VusVus
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  • A. Bay Beijng October 200537 CKM matrix.3 downstrange beauty up 0.97 0.22 0.002 charm 0.22 0.97 0.03 top 0.004 0.03 1 + O( 4 ) = sin( Cabibbo ) =0.224 A=0.830.02 phase: change sign under CP parametrized by 4 real numbers (not predicted by the SM). Need to measure them. Magnitude ~ Wolfestein (1983)
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  • A. Bay Beijng October 200538 CKM matrix.4 downstrange beauty up 0.1% 1% 17% charm 7% 15% 5% top 20% ?% 29% V ij )/ V ij ~ Today precision from direct measurements, no unitarity imposed:
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  • A. Bay Beijng October 200539 CKM matrix.5 + O( 4 ) downstrange beauty up 0 0 115 charm 0 0 0 top 25 0 0 Phase ~ downstrange beauty up 0 0 115 charm 0 0 0 top 25 0 0 Wolfestein (1983)
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  • A. Bay Beijng October 200540 CKM Matrix and the Unitary Triangle(s) SM Unitarity V ji *V jk = ik V ud V ub + V cd V cb + V td V tb = 0 V ud V ub V td V tb * V cd V cb * * The Unitary Triangle Triangle Re Im
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  • A. Bay Beijng October 200541 Re Im 1 CKM Matrix and the Unitary Triangle(s).2 + O( 4 ) SM Unitarity V ji *V jk = ik V ud V ub + V cd V cb + V td V tb = 0 The Unitary Triangle Triangle after normalization by V cd V cb *=A 3
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  • A. Bay Beijng October 200542 Experimental program: measure sides and angles * CP violated in the SM => the area of triangle 0 * Any inconsistency could be a signal of the existence of phenomena not included in the SM ~V ub ~V td ~V cb Use B mesons phenomenology t quark oscillations CP asymmetries b quark decays
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  • A. Bay Beijng October 200543 Why do we expect some NEW PHYSICS ? * SM has 18 free parameters (more with massive neutrini), in particular masses and CKM parameters are free. * Some of the neutrinos have masses>0. * Why the electric charge is quantized ? * The choice of SU(2)U(1) is arbitrary. * Gravitation is absent. * Problems in Cosmology: What is the nature of dark matter and dark energy ? Baryogenesis does not work in the SM: The SM amount of CP violation is too low The requirement of non-equilibrium cannot be obtained with heavy Higgs => new light scalar must exist
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  • A. Bay Beijng October 200544 Cosmics
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  • A. Bay Beijng October 200545 masses & mixings In the SM, CPV is related to the mass generation mechanism for the fermions. The fermionic system is far from being understood. Is there any "periodicity" in the mass spectrum? Similar question for the mixing matrices.
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  • A. Bay Beijng October 200546 Any horizontal symmetry ? CPV, mix., baryogenesis: hep-ph/0108216v2 * Neutrino mix and CPV in B: hep-ph/0205111v2 Bs-Bs mixing in SO(10) SUSY GUT linked to mix. hep-ph/0312145 A. Buras, J. Ellis, M.K. Gaillard and D.V. Nanopoulos, Nucl. Phys. B135 (1978) 66 Lepton-quark mass relations first (?) discussed by V H ( CKM ) ( NMS ) ?
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  • A. Bay Beijng October 200547 Models beyond the SM SM is believed to be a low-energy effective theory of a more fundamental theory at a higher energy scale (compare situation of classical mechanics and relativistic). Grand Unified Theory (GUT) theories have been suggested to cope with (some of) the SM problems. They predicts that the coupling constants meet at EGUT~10 15-16 GeV EW SSB: SU(2) L U(1) Y U(1) em g GUT you are here
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  • A. Bay Beijng October 200548 SUSY particle superparticle The Minimal Supersymmetric extension of the SM (MSSM) with gauge coupling unification at E GUT = 10 16 GeV predicts the EW mixing parameter: sin 2 W = 0.2336 0.0017 to be compared with the experiemental value sin 2 W = 0.231200.00015. The model predicts the existence of new particles.
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  • A. Bay Beijng October 200549 How to detect New Physics ? Direct searches: search for new particles, for instance the supersymmetric partners of particles. New phenomenologies, indirect effects: ex.1: proton decay ex.2: EDM measurement ex.3: Hadronic flavour physics very powerful (think to KM prediction of 3 quark families). It can in principle probe very high energies (think to the Z was "seen" in low ener