Applications of effective Lagrangians

This thesis contains some applications of effective field theories in particle physics. The impact of a fourth generation of quarks on neutral kaon mixing is considered, and the results are extended to the mixing and CP violating phenomenology of neutral bottom meson systems. A phenomenological Lagrangian is constructed to describe radiative vector meson decays. The measured decay rates are reproduced, and one prediction is made. It is shown that the large-N approximation in the standard model cannot explain the ΔI = 1/2 rule for kaon nonleptonic decays, even when short distance effects such as Penguins are included. Finally, the contribution of small instantons to the axion potential is calculated. The induced potential can be a large if the QCD coupling is non-decreasing at high energies, and if a suppression by light quark masses can be avoided using loops of scalars