Flavour constraints on sequestered supersymmetry breaking in string models

The Standard Model (SM) is the best theory which describes Nature at the fundamental level. Even if it provides very accurate predictions, the SM features some open problems. A promising extension of the SM is the Minimal Supersymmetric Standard Model (MSSM) provided by supersymmetry. The MSSM can provide solutions for some of the open problems of the SM but it can suffer from the flavour supersymmetric problem associated with the presence of large Flavour Changing Neutral Currents (FCNCs). The flavour supersymmetric problem is related to the mechanism which mediates supersymmetry breaking from the hidden to the visible MSSM sector. A popular supersymmetry breaking mediation mechanism is gravity mediation but generic gravity mediated models lead to large FCNCs. The conditions to avoid FCNCs in gravity mediated models are called mirror mediation. These conditions can naturally be satisfied in 4D string compactifications. 4D string models introduce new scalar particles, the moduli, which interact gravitationally with matter and represent natural candidates to mediate supersymmetry breaking to the MSSM. Promising 4D string scenarios are sequestered models where the MSSM lives on branes at singularities and the visible sector is sequestered from the sources of supersymmetry breaking in the bulk of the extra dimensions. So one can realise low-energy supersymmetry and all moduli can be heavy enough to avoid any cosmological moduli problem. In this thesis we shall focus on 4D sequestered string scenarios and determine which models can reproduce mirror mediation without the production of large FCNCs. We will find two different classes of sequestered models where only one can be compatible with present flavour constraints on FCNCs. This comparison with observations will provide information on important details of the microscopic theory like the functional dependence on the extra-dimensional volume of the physical Yukawa couplings and the Kähler potential for matter fields.