Seminarium "Teoria cząstek elementarnych i kosmologia"

In this talk, I explore some aspects of extended Higgs sectors that lead to exact mass degeneracies among some of the physical scalars. Natural scalar mass degeneracies are possible in the inert two Higgs doublet model (IDM). In the case of three doublets, I present an extension of the IDM and then generalize this model to obtain a scalar potential, first proposed by Ivanov and Silva (IS), with a CP4 symmetry that guarantees the existence of pairwise degenerate scalar states among the neutral and charged Higgs scalars. The symmetries of the model permit a term in the IS scalar potential with a complex coefficient that cannot be removed by any redefinition of the scalar fields within the class of Higgs bases (in which case, we say that no real Higgs basis exists and the conventional CP symmetry is absent). Moreover, I show that it is possible to physically distinguish between the existence or nonexistence of a real Higgs basis in the IS model despite the fact that no CP-violating observables exist in either case.