1 / 58

Summary

Summary. 1. Some history 2. Antiparticles 3. Standard Model of Particles (SM ) Discrete symmetries, CP violation, Connection with Cosmology Fermionic mass generation mechanism, Why do we think that the SM is not the final word ?. The Standard Model. e.m. charge [e].

ruby
Download Presentation

Summary

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Summary 1. Some history 2. Antiparticles 3. Standard Model of Particles (SM) Discrete symmetries, CP violation, Connection with Cosmology Fermionic mass generation mechanism, Why do we think that the SM is not the final word ? A. Bay Beijing October 2005

  2. The Standard Model e.m. charge [e] MATTER INTERACTIONS n n n Weak : W+ W- Z e m t 0 - - - e 1 m t - E.M. : photon u c t 2/3 Quarks 1/3 d s b - Strong : gluons Spin 1/2 Spin 1 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... ! A. Bay Beijing October 2005

  3. Discrete symmetries Parity: left Charge particle antiparticle conjugation Temporal inversion right A. Bay Beijing October 2005

  4. symmetry violation Some symmetries might have a deep reason to exist ... other not. ... suddenly we discover that we can observe a "non - observable". A is discovered. The Right-Left symmetry (Parity) was considered an exact symmetry  1956 A. Bay Beijing October 2005

  5. Discrete symmetries P and C P: (x,y,z) -> (-x,-y,-z). C: charge -> -charge. angular momentum, spin. e.m. interactions are P & C invariant A. Bay Beijing October 2005

  6. What about T ? If x(t) is solution of F = m d2x/dt2 then x(-t) is also a solution (ex.: billiard balls) Ok with electrodynamics: A. Bay Beijing October 2005

  7. Parity: (x,y,z)  (-x,-y,-z) 1848 L. Pasteur discovers the property of optical isomerism. Mirror symmetry The synthesis of the lactic acid in the lab gives a "racemic" mixture: Nleft molecules = Nright molecules (within statistic fluctuations) Asymmetry = This reflects the fact that e.m. interaction is M (and P) invariant A. Bay Beijing October 2005

  8. Parity violation in biology snif snif Humans are mostly right handed: Asymmetry  A = (NR-NL)/(NR+NL) ≈ 0.9  “90%Parity violation" Lemmon and orange flavours are produced by the two "enantiomers" of the same molecule. A. Bay Beijing October 2005

  9. 100% P violation in DNA A. Bay Beijing October 2005

  10. Too much symmetry... LR LL RR A. Bay Beijing October 2005

  11. Partial R-L symmetry in Rome ? Bacchus, Arianna ? MUSEE ROMAIN DE NYON A. Bay Beijing October 2005

  12. Some asymmetry introduces more dynamics A. Bay Beijing October 2005

  13. P conserved in e.m. and strong interacctions 1924 O. Laporte classified the wavefunctions of an atom as either even or odd, parity +1 or -1. In e.m. atomic transitions a photon of parity -1 is emitted. The atomic wavefunction must change to keep the overall symmetry constant (Eugene Wigner, 1927) : Parity is conserved in e.m. transitions This is also true for e.m. nuclear or sub-nuclear processes (within uncertainties). H(strong) and H(e.m.) are considered parity conserving. A. Bay Beijing October 2005

  14. Parity in weak interactions * E. Fermi, 1949 model of W interactions: P conservation assumed *C.F. Powell,... observation of two apparently identical particles "tau" and "theta" weakly decaying tau 3 pions theta 2 pions which indicates P(tau) = -1 and P(theta) = + 1 If Parity holds "tau" and "theta" cannot be the same particle. *HEP conf. Rochester 1956 Tsung Dao Lee and Chen Ning Yang suggest that some particles can appear as parity doublets. Feynman brought up the question of non-conservation of parity (but bets 50 $ that P is conserved). Wigner suggests P is violated in weak interactions. A. Bay Beijing October 2005

  15. Parity in weak interactions .2 Lee and Yang make a careful study of all known experiments involving weak interactions. They conclude "Past experiments on the weak interactions had actually no bearing on the question of parity conservation" Question of Parity Conservation in Weak Interactions T. D. Lee Columbia University, New York, New York C. N. Yang Brookhaven National Laboratory, Upton, New York The question of parity conservation in beta decays and in hyperon and meson decays is examined. Possible experiments are suggested which might test parity conservation in these interactions. Phys. Rev. 104, 254–258 (1956) A. Bay Beijing October 2005

  16. Co 60 J Co p 1956 C. S. Wu et al. execute one of the experiments proposed by Lee and Yang. Co60 at 0.01 K in a B field. Observables: a "vector" : momentum p of beta particles an "axial-vector" : spin J of nucleus (from B). Compute m = <Jp> In a P reversed Word: P: Jpa-Jp P symmetry implies m = 0 J p Co m was found  0  P is violated A. Bay Beijing October 2005

  17. 152 Sm Counter g n 152 Sm NaI Polarimeter: selects g of defined helicity Measurement of neutrino helicity (Goldhaber et al. 1958) Result: neutrinos are only left-handed A. Bay Beijing October 2005

  18. Parity P and neutrino helicity P left n n right P symmetry violated at (NL-NR)/(NL+NR) = 100% A. Bay Beijing October 2005

  19. Charge conjugation C C left n - left n C transforms particles  antiparticle C symmetry violated at 100% A. Bay Beijing October 2005

  20. Last chance: combine C and P ! CP left right Is our Universe CP symmetric ? A. Bay Beijing October 2005

  21. (A)symmetry in the Universe matter Big Bang antimatter Big Bang produced an equal amount of matter andantimatter Today: we live in a matter dominated Universe time A. Bay Beijing October 2005

  22. Baryo genesis Big Bang models are matter/antimatter symmetric Where is ANTIMATTER today? 1) Anti-Hydrogen has been produced at CERN: antimatter can exist. 2) Moon is made with matter. Idem for the Sun and all the planets. 3) In cosmics we observe e+ and antiprotons, but rate is compatible with secondary production. 4) No sign of significant of e+e-annihilation in Local Cluster. 5) Assuming Big Bang models OK, statistical fluctuations cannot be invoked to justify observations. No known mechanism to separate matter and antimatter at very large scale e+e- annihilation in the Galaxy A. Bay Beijing October 2005 in the Univers !

  23. AMS sensitivity (0.5 - 20 GeV): He/He ~10-9 C/C ~10-8 A. Bay Beijing October 2005

  24. Baryogenesis .2 N protons £ 5 10 -8 2.5 10 -10 £ N photons -6 3 -6 3 =0.1 =1 10 GeV/cm 10 p/cm r r  matter C Today (age of Univers 10-20 109 years): no significant amount of antimatter has been observed. The visible Universe is maid of protons, electrons and photons The N of photons is very large compared to p and e A. Bay Beijing October 2005

  25. Baryogenesis .3 3 ( ) kT 2 3 N 412 photons/cm  1.202 = 2.7 2 ch p Sky T observed by COBE~ 2.7K This suggests a Big Bang annihilation phase in which matter + antimatter was transformed into photons... A. Bay Beijing October 2005

  26. Baryogenesis.4 A. Bay Beijing October 2005

  27. Baryogenesis.5 Starting from a perfectly symmetric Universe: 3 rules to induce asymmetry during evolution 1) $ processes which violate baryonic number conservation: B(t=0) = 0 B(today)>0 B violation is unavoidable in GUT. Andrej Sakarov 1967 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 ?) A. Bay Beijing October 2005

  28. Baryogenesis .6 q q ou + q e 27 10 { °K q q X ou - q e - + Prob(X qq) = Prob(X qe ) = (1  a  -a) - - - - Prob(X qq) = Prob(X qe ) = (1  b  -b) - - - X qq  X CP mirror Requirement: a > b... ... forbidden by CP symmetry ! CP X  qq  a = b A. Bay Beijing October 2005

  29. CP violation + - e p n { MIRROR provides an absolute definition of + charge CP - + e p n - + + - e N p n e p n - + + - N e e p n p n July 1964: J. H. Christenson, J. W. Cronin, V. L. Fitch et R. Turlay find asmall CP violation with K0 mesons!!! S. Bennet, D. Nygren, H. Saal, J. Steinberg, J. Sunderland (1967): K 0 L K 0 L 0 K is its own antiparticle L CP symmetry implies identical rates. Instead... - N % 0.3  + N A. Bay Beijing October 2005

  30. CP violation experiment A. Bay Beijing October 2005

  31. CPLear K0 K0 Processes should be identical but CPLear finds that neutral kaon decay time distribution  anti-neutral kaon decay time distribution Other experiments: NA48, KTeV, KLOE f factory in Frascati, ... A. Bay Beijing October 2005

  32. NA48 decay channel The Kaon decay channel of the NA48 experiment at CERN - the latest study to provide a precision measurement of CP violation. A. Bay Beijing October 2005

  33. CPT Schwinger-Lüders-Pauli show in the '50 that a theory with locality, Lorentz invariance spins-statistics is also CPT invariant. Consequences: * Consider particle y at rest. Its mass is related to:  particle and antiparticle have same mass (and also same life time, charge and magnetic moment) * If a system violates CP T must be violated,... A. Bay Beijing October 2005

  34. T from CPLear oscillations s t d W W K0 s d t K0 0 (6.61.6)10-3 A. Bay Beijing October 2005

  35. Electric Dipole Moments Energy shift for a particle with EDM d in a weak electric field E is linear in E: DE = E d . d can be calculated from d =  ri qi which is left unchanged by T: q aq T: rar Consider a neutron at rest. The only vector which characterize the neutron is its spin J. If a non-zero EDM exists in the neutron: d = k J Under time reversal T: Ja-J This implies k = 0 if T is a good symmetry: d = 0 A. Bay Beijing October 2005

  36. E D M 2 expt [e cm] SM prediction proton ( - 4  6 ) 10-23 10-31 neutron < 0.63 10-25 ( 95% CL) 10-31 electron ( 0.07  0.07 ) 10-26 10-38 muon ( 3.7  3.4 ) 10-19 10-35 129-Xe <10-27 199-Hg <10-28 muon measurement in future "neutrino factories"  10-24 No signal of T violation "beyond the Standard Model" so far ! A. Bay Beijing October 2005

  37. CP & T violation only in K0 system ??? Since 1964, CP and or T violation was searched for in other systems than K0, other particles decays, EDM... No other signal until 2001. In 2001 Babar at SLAC and Belle at KEK observe a large CP vioaltion in the B0-B0bar system A. Bay Beijing October 2005

  38. Origin of CP violation Hamiltonian H = H0 + HCP with HCP responsible for CP violation. Let's take HCP = 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 HCP CP† = CP (gH + g*H†) CP† = gH† + g*H CP invariance : HCP = CP HCP 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. A. Bay Beijing October 2005

  39. CP violation and SM Up type quark spinor field Q = 2/3 Down type quark spinor field Q = -1/3 u c t d s b SM does not predict these parameters... SM with 3 families canaccommodate CP violation in the weak interactions through the complexCabibbo-Kobayashi-Maskawa quark mixing matrix VCKM, with 4 parameters. I II III A. Bay Beijing October 2005

  40. In the '60 ... u W Vus s Parameters Vij are used to calculate the transitions quark(i)  quark(j) first introduced by N. Cabibbo for i,j=u, d, s Thequark c was introduced in 1970 (GIM), discovered in 1974. In the 1970 the "flavour mixing" matrix was VCabibbo= • cabibbo ~ 12° VCabibbo is real, while CPV implies that some of the Vij complex ! A. Bay Beijing October 2005

  41. CKM matrix CPV implies that some of the Vij complex. In 1972 Kobayashi & Maskawa show that, in order to generate CP violation (i.e. to get a complex phase), V must be (at least) 3x3  this is a prediction of the three quark families of the SM: (u, d), (c, s), (t, b) In the SM, with 3 and only 3 families of quarks, the matrix must be unitary VCKM= The last quark, t, was observed 25 years later ! A. Bay Beijing October 2005

  42. CKM matrix in the SM L= LW,Z + LH + LFermions + Linteraction LFermions contains the (Yukawa) mass terms: MU and MD complex matrices, diagonalized by a couple of non-singular matrices, to get the physical mass values: A. Bay Beijing October 2005

  43. CKM matrix .2 u W Vus s After the transformation (idem for D quarks) e.m. and neutral currents unaffected. The charged currents are modified: "mixing matrix" V unitary A. Bay Beijing October 2005

  44. CKM matrix .3 phase: change sign under CP • = sin(qCabibbo) =0.224 A=0.83±0.02 + O(l4) Wolfestein (1983) parametrized by 4 real numbers (not predicted by the SM). Need to measure them. down strange beauty up 0.97 0.22 0.002 charm 0.22 0.97 0.03 top 0.004 0.03 1 Magnitude ~ A. Bay Beijing October 2005

  45. CKM matrix .4 Today precision from direct measurements, no unitarity imposed: s(|Vij|)/|Vij| ~ down strange beauty up 0.1% 1% 17% charm 7% 15% 5% top 20% ?% 29% A. Bay Beijing October 2005

  46. CKM matrix .5 down strange beauty up 0 0 115° charm 0 0 0 top 25° 0 0 down strange beauty up 0 0 -115° charm 0 0 0 top -25° 0 0 + O(l4) Wolfestein (1983) Phase ~ A. Bay Beijing October 2005

  47. CKM Matrix and the Unitary Triangle(s) The Unitary Triangle * VcdVcb SM UnitarityVji*Vjk=dik VudVub + VcdVcb + VtdVtb = 0 Re VtdVtb * a(f2) * VudVub b(f1) g(f3) Im A. Bay Beijing October 2005

  48. CKM Matrix and the Unitary Triangle(s) .2 Im h a(f2) The Unitary Triangle g(f3) b(f1) Re r 1 + O(l4) SM UnitarityVji*Vjk=dik VudVub + VcdVcb + VtdVtb = 0 after normalization by VcdVcb*=Al3 A. Bay Beijing October 2005

  49. Experimental program: measure sides and angles a b quark t quark ~Vub g b ~Vtd decays ~Vcb oscillations CP asymmetries * 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 Use B mesons phenomenology A. Bay Beijing October 2005

  50. 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 A. Bay Beijing October 2005

More Related