The decays B→ Xsγ, B→ Xsgluon and B →Xsμ+μ- in universal extra dimensions and mass corrections in dimensional deconstruction

In this thesis an extension of the Standard Model of particle physics in Universal Extra Dimensions (UED) is discussed. The flavour-changing neutral current (FCNC) decays B → Xsγ, B → Xs gluon and B → Xsμ+μ- are used to constrain the compactification scale 1/R in the model introduced by Appelquist, Cheng and Dobrescu (ACD). Values of 1/R ≥ 300 GeV are found to be consistent with experimental data. In addition, the ultraviolet completion of UED models in the framework of Dimensional Deconstruction is investigated. In particular, the realization of chiral fermions and the issue of Kaluza-Klein parity is discussed. The calculated radiative corrections of fermion masses permit to draw conclusions on the renormalizability and structure of the fundamental Lagrangian. Moreover, the running contribution to the fermion masses from the cut-off scale is extracted and compared to the result in the corresponding continuum theory. (orig.)