Supersymmetric Models with a hierarchical squark spectrum and a heavy Higgs boson

Low energy Supersymmetry is one of the best motivated extensions of the Standard Model of Particle Physics. Here we focus on a particular supersymmetric framework, taking the masses of the squarks of the rest two generations much larger than the others and a Higgs boson mass in the (200 ÷ 300) GeV range. The motivation is twofold: on the one hand a high mass scale for the squarks of the rest two generations allows at least to soften the Supersymmetric Flavour problem; on the other hand, a higher Higgs boson mass allows to explain the lack of signals in the Higgs sector. In Chapter 1 we summarise the main features of supersymmetric models at the Fermi scale and we identify the problems that shall be the subject of this thesis. In Chapter 2 we will consider the "Higgs boson mass problem" and the "Supersymmetric Flavour problem" as related naturalness problems. In Chapter 3 some phenomenological aspects of supersymmetric theories with such a "non standard" sparticle spectrum will be studied, namely gluino decays, production and decay rates of the lightest Higgs boson and some aspects relevant for the Dark Matter direct detection. At last, in Chapter 4, we will turn our attention to flavour signals, implementing an eff ective Minimal Flavour Violation in the case of a hierarchical squark spectrum and deriving lower bounds on the masses of the heavy squarks that allow to have agreement with experiments. The overall conclusions are summarised in Chapter 5.