1. P461 - particles VII1 Glashow-Weinberg-Salam Model EM and weak forces mix…or just EW force. Before mixing Bosons are massless: Group Boson Coupling Quantum No. SU(2) L W 1,2,3 g T weak isospin U(1) B g’ Y leptonic hypercharge Interaction Lagrangian is convert to physical fields. Neutrals mix (B,W3->Z, photon). W,Z acquire mass. Force photon mass=0. Higgs Boson introduced to break mass symmetry (A same field as in EM….4 vector)

2. P461 - particles VII2 Look at EM and 2 weak “current” charged current. Compare to mu/beta decay (have measured weak force, eg. weak mixing only “new” free parameter) weak neutral current

3. P461 - particles VII3 W and Z couplings EW model has left-handed doublets right handed singlets W couplings to left-handed component and ~always the same Z to left-handed doublet Z to right-handed singlet redefine as Vector and Axial parts of V-A Z

4. P461 - particles VII4 Z decays/vertices Color factor of 3 for quarks

5. P461 - particles VII5 Z Branching Fraction Can use couplings to get branching modes PDG measured values in ()