Supercomposite Models and Rare Processes

This thesis will deal mainly with induced contact interactions in composite and supercomposite models that might contribute to various rare processes, most notably flavour-changing interactions. By supercomposite, we refer to composite models that have an underlying supersymmetry. Whereas a purely composite model can have induced four-fermion dimension-six operators suppressed by the square of the composite mass scale, supercomposite models can have induced dimension-five two-scalar, two-fermion induced interactions suppressed by only one power of the composite mass scale. The two-scalars would be the supersymmetric scalar partners of the fermions, and therefore this interaction could be "dressed" to a four-fermion interaction through the exchange of a gaugino (the supersymmetric partners of gauge bosons). This would lead to effective four-fermion interactions suppressed by one power each of the composite and supersymmetric mass scales. If the supersymmetric mass scale is significantly lower than the composite mass scale, this can lead to constraints on the composite mass scale that are much more restrictive than constraints on pure composite models. We investigate the processes, pi _{21} decay, muon conversion ( muNtoeN), the K_{rm L}-K _{rm S} mass difference (and B-B mixing), and the neutron electric dipole moment. For each of these processes we first set limits on the square of the composite mass scale from dimension-six operators induced by a pure composite model. We then set limits on the product of the composite and supersymmetric mass scales from possible supercomposite interactions. Also in this thesis we investigate possible contributions to the decays btosgamma and btosmu ^+mu^- by an anomalous W quadrupole moment. Such an anomalous quadrupole moment is often suggested in composite gauge boson theories. By using the experiment limits on the decay BtoK* gamma, we can constrain the coupling constant associate with this quadrupole moment to, | lambda_gamma| <= 10 for a top mass of 135 GeV. Further improvements on this limit could constrain the value to be | lambda_gamma| <= O(1).