Flavour Physics in two-Higgs-doublet models

Despite the tremendous success of the Standard Model, the arguments for the necessity of an extension are compelling. An attractive option is provided by Two-Higgs-Doublet models, due to their simplicity and them being the low-energy limit of some more complete theories. In the most general version of the model, the fermionic couplings of the neutral scalars are non-diagonal in flavour and, therefore, generate unwanted flavour-changing neutral-current phenomena. Different ways to suppress FCNCs have been developed, giving rise to a variety of specific implementations of the 2HDM. Three of these are discussed in this talk, comparing their phenomenological influence in flavour observables: The use of a discrete Z2-symmetry, an expansion around this limit in a minimal flavour violation scenario assuming the decoupling limit, and the Aligned Two-Higgs-Doublet Model. All of these result in the absence of tree-level flavour-changing neutral currents. Their different phenomenological consequences are demonstrated for a selection of observables, namely (semi-) leptonic decays, B->X_s gamma and mixing in the B0_d,s-systems.

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