Resonant H and A Mixing in CP-noninvariant 2HDM and MSSM

In the general two--Higgs--doublet model, including the minimal supersymmetric standard model (MSSM) as its specific realization, the two heavy neutral Higgs bosons are nearly degenerate in the decoupling limit. If the theory is CP--noninvariant, the mixing between the heavy states can strongly be affected by the decay widths. We develop the formalism describing this CP--violating non--hermitian mixing and provide some interesting experimental signatures of the CP--violating mixing at a $\gamma\gamma$ collider with polarized beams in the context of the CP--noninvariant MSSM.