  The present Thesis is dedicated to a formal and phenomenological
investigation of extensions to two separate sectors of the Standard Model of
particle physics (SM): the electroweak sector and the strong sector. The Thesis
is divided into two main parts: Part I focuses on the Lee-Wick Standard Model
(LW SM), which, by providing a solution to the Hierarchy problem, forms a
natural extension of the electroweak sector, while Part II studies the coloron
theory, arising from extending the strong sector gauge group. Providing a
general introduction about the current state of the SM and the associated
challenges in Chapter 1, we proceed in Chapter 2 to analyze the tension between
naturalness and isospin violation in the LW SM. Chapter 3 discusses the global
symmetries and the renormalizability of LW scalar QED. A first complete
calculation of QCD corrections to the production of a massive color-octet
vector boson (colorons) is reported in Chapter 4. Finally, we conclude the
Thesis in Chapter 5 by summarizing the discussed results and presenting an
outlook for future research in the surveyed areas.
