The two-gluonic decay modes ofW andZ in the broken colour model with integrally charged quarks are considered. The gluonic branching ratios are found to be 3% and 2·7% forW andZ respectively. The angular distributions of the decays ofW andZ to two jets of hadrons are also worked out.

We point out that the equivalent-photon approximation (EPA) for processes with massive spin-1 particles in the final state would have validity in a more restricted kinematic domain than for processes where it is commonly applied, viz., those with spin-1/2 or spin-0 particles in the final state. We obtain the criterion for the validity ofEPA for the two-photon production of a pair of charged, massive, point-like spin-1 particlesV^±, each of massM and with a standard magnetic moment (κ=1). In a process in which one of the photons is real and the other virtual with four-momentumq, the condition for the validity ofEPA is |q²|≪M², in addition to the usual condition |q²|≪W²,W being theV⁺V⁻ invariant mass. In a process in which both photons are virtual (with four-momentaq andq′), our condition is |q²||q′²|W⁴ ≪ 16M⁸, in addition to |q²| ≪M², |q′²| ≪M² and |q²| ≪W², |q′²| ≪W². Even when these extra conditions permitting the use ofEPA are not fulfilled, convenient approximate expressions may still be obtained assuming merely |q²| ≪W² and |q′²| ≪W².

We also discuss how the extra conditions are altered when the vector bosons are incorporated in a spontaneously broken gauge theory. Examples ofW boson production in Weinberg-Salam model are considered for which the condition |q²||q′²|W⁴ ≪ 16M⁸ is shown to be removed.

The concept of discrete symmetries in classical and quantum physics is reviewed. An account is given ofCP violation observed in theK-meson system and of other experiments whereCP symmetry has been tested. The present theoretical ideas onCP violation within the standard model, and problems needing extension of the model are described. Finally, ideas and experimental approaches toCP violation beyond the standard model are reviewed in brief.

This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently.